【拆分】【拆分】教材 Intensive Respiratory Care _82-188_1-98

WEANING 断乳

WEANING FROM MECHANICAL VENTILATION
机械通气脱机

DEFINITION 定义

Ventilator weaning may be defined as the discontinuation of mechanical ventilation in patients with acute respiratory failure, based upon predetermined, objective criteria and accompanied by appropriate physiological monitoring. By analogy to the original use of the verb, to wean, ventilator weaning often implies a gradual progressive withdrawal of support. It need not have this implication, however, and many patients requiring mechanical ventilation following surgery or for other brief indications can simply have the ventilator turned off. The application of objective physiological criteria in predicting and monitoring successful ventilator discontinuation, however, is important to the best possible respiratory care of patients and central to the concept of weaning as described here.
呼吸机脱机可定义为急性呼吸衰竭患者根据预先确定的客观标准停止机械通气，并伴有适当的生理监测。与动词 to wean 的原始用法类似，呼吸机脱机通常意味着逐渐逐渐退出支持。然而，它不需要有这种含义，许多手术后需要机械通气或其他短暂指征的患者可以简单地关闭呼吸机。然而，在预测和监测成功停用呼吸机时应用客观生理标准对于患者的最佳呼吸护理很重要，并且是本文所述脱机概念的核心。

Figure 15-1 diagrammatically shows the traditional forms of ventilator weaning. When continuous ventilation is employed in the assist/control mode (AMV), the patient receives all required minute ventilation (VE) from the ventilator; when this is withdrawn (Fig. 15-1A), the patient must then supply all required Ve spontaneously. This is known as traditional, or short, ventilator weaning. Using this technique, patients can also be weaned gradually through a series of brief periods of spontaneous ventilation interspersed with rest periods of AMV (Fig. 15-1B). When intermittent mandatory ventilation (IMV) is used in weaning after AMV, the proportion of machine-supplied ventilation is progressively diminished from 100 per cent to zero (Fig. 15-1C). When IMV has been the primary mode of ventilatory support, weaning is accomplished by further reducing a machine minute volume that was already only a portion of the patient’s required VE (Fig. 15-1D).
图 15-1 以图示方式显示了呼吸机脱机的传统形式。当在辅助/控制模式（AMV）下采用持续通气时，患者从呼吸机获得所有必需的分钟通气（VE）;当它被撤回时（图 15-1A），患者必须自发地提供所有需要的 Ve。这被称为传统或短呼吸机脱机。使用这种技术，患者也可以通过一系列短暂的自主通气和穿插 AMV 的休息时间逐渐撤机（图 15-1B）。当 AMV 后断奶时使用间歇指令通气（IMV）时，机器供给通气的比例从 100% 逐渐减少到零（图 15-1C）。当 IMV 成为通气支持的主要模式时，通过进一步减少机器的微小体积来完成脱机，而机器的体积已经是患者所需 VE 的一部分（图 15-1D）。

Pressure support ventilation (PSV) may be added to either of the traditional weaning regimens just described and has the effect of partially supporting the patient’s spontaneous breathing efforts.
压力支持通气（PSV）可以添加到刚才描述的任何一种传统脱机方案中，并具有部分支持患者自主呼吸努力的效果。

Figure 15-1. Traditional weaning techniques.

A

, Short T-piece weaning, in which full ventilatory support with assist-control (AMV) is simply stopped.

B

, Gradual weaning using the T-piece technique. Brief periods of spontaneous ventilation are gradually lengthened, with intervening rest periods with full ventilatory support (with either AMV or IMV).

C

, Weaning from full ventilatory support using the intermittent mandatory ventilation (IMV) technique. As compared with

A

, this technique starts earlier and completes weaning at about the same time.

D

, Gradual weaning from IMV (used as a primary ventilator mode) using IMV (used in weaning). Conceptually, the duration of mechanical ventilation is the same in

A

as in

C

, and the same in

B

as in

D

. Pressuresupport can be added to any of these scenarios and has the effect of partially supporting the patient by reducing the work of breathing. The pressure support itself must subsequently be weaned.

\dot{V} E =

total minute ventilation;

^{*} =

weaning begun;

↑=

weaning complete.
图 15-1.传统的脱机技术。

A

，短 T 型脱机，其中简单地停止带有辅助控制（AMV）的全面通气支持。

B

，使用 T 型件技术逐渐断奶。短暂的自主通气时间逐渐延长，中间休息时间，完全通气支持（使用 AMV 或 IMV）。

C

，使用间歇指令通气（IMV）技术从完全通气支持中撤机。与

A

相比，该技术开始得更早，并几乎同时完成断奶。

D

，使用 IMV（用于脱机）逐渐从 IMV（用作主要呼吸机模式）脱机。从概念上讲，机械通气的持续时间与

A

中相同，与

B

中

C

D

相同。压力支持可以添加到这些情况中的任何一种，并且具有通过减少呼吸功来部分支持患者的效果。压力支持本身随后必须撤机。

\dot{V} E =

总分钟通气量;

^{*} =

断奶开始;

↑=

断奶完成。

Pressure support can also be used as a stand-alone, third basic weaning strategy: Enough PSV is added to provide a tidal volume (VT) equivalent to that used with AMV or IMV, and then the added inspiratory pressure is progressively withdrawn as tolerated by the patient.
压力支持也可以用作独立的第三种基本脱机策略：添加足够的 PSV 以提供与 AMV 或 IMV 相当的潮气量（VT），然后根据患者耐受情况逐渐撤回增加的吸气压力。

ASSESSMENT FOR WEANING 脱机评估

Oxygenation 氧合

For successful weaning from mechanical ventilation, the patient’s respiratory function should be adequate to saturate arterial blood at an inspired oxygen fraction (

{FIO}_{2}

) of 0.50 or less. Patients with larger oxygenation defects usually require further treatment of their primary disease process before weaning can be accomplished successfully.
为了成功从机械通气脱机，患者的呼吸功能应足以使吸入氧分数（

{FIO}_{2}

）为 0.50 或更低时使动脉血饱和。氧合缺损较大的患者通常需要进一步治疗其原发疾病过程，然后才能成功完成脱机。

Ventilatory Demand 通气需求

Patients requiring more than twice the normal VE in order to maintain a normal

{PaCO}_{2}

usually have significantly elevated

{CO}_{2}

production

({VCO}_{2})

, dead space fraction

(Vd / VT)

, or both. Therapy therefore should continue in an attempt to normalize these prior to weaning. Excessive

{VCO}_{2}

from sepsis, burns, or other hypermetabolic processes often prevents successful weaning despite adequate ventilatory mechanics. Similarly, a very high Vd/Vt, as is seen in the adult respiratory distress syndrome (ARDS), severe asthma, or massive pulmonary embolism, may prevent weaning from the ventilator despite adequate oxygenation and ventilatory mechanics.
需要两倍于正常 VE 才能维持正常

{PaCO}_{2}

的患者通常具有显著升高

{CO}_{2}

的生成

({VCO}_{2})

、死腔分数

(Vd / VT)

或两者兼而有之。因此，应继续治疗，以尝试在脱机前使这些恢复正常。脓毒症、烧伤或其他代谢亢进过程导致的过量

{VCO}_{2}

通常会阻止成功脱机，尽管有足够的通气机械。同样，非常高的 Vd/Vt，如成人呼吸窘迫综合征（ARDS）、严重哮喘或大面积肺栓塞，尽管有足够的氧合和通气机械装置，但仍可能会阻止脱离呼吸机。

Ventilatory Mechanics 通气力学

Perhaps the best overall indicator of a patient’s ability to sustain spontaneous ventilation following acute respiratory failure is the respiratory rate. Results of numerous studies show that measures of a patient’s ventilatory mechanics during spontaneous breathing for a minute or two can also be used in predicting weaning success, at least following short-term ventilatory support. Although many measurements have been used, the most clinically valuable are also the easiest to do, requiring only a bedside spirometer and a manometer. These devices quantitate the strength of the respiratory muscles [maximal inspiratory force (MIF)]; the adequacy of ventilatory mechanics [vital capacity (VC)] and tidal volume (VT); the ability of the patient to match with spontaneous breathing the VE furnished by the ventilator; and the patient’s capacity to increase this Ve on demand. This final measurement is the maximal voluntary ventilation (MVV). To obtain the MVV, the patient is instructed to breathe as vigorously as possible for 10 or 12 seconds, and the resultant volume is multiplied to obtain a theoretical minute volume. This tests not only mechanics and muscle strength but also comprehension and cooperation, factors that also affect weaning success.
也许患者在急性呼吸衰竭后维持自主通气能力的最佳总体指标是呼吸频率。大量研究的结果表明，至少在短期通气支持后，患者自主呼吸一两分钟期间的通气力学测量也可用于预测脱机成功。尽管已经使用了许多测量方法，但最具临床价值的测量也是最容易进行的，只需要一个床旁肺活量计和一个压力计。这些设备量化呼吸肌的力量 [最大吸气力（MIF）];通气力学 [肺活量（VC）] 和潮气量（VT）的充足性;患者与呼吸机提供的 VE 相匹配的能力;以及患者按需增加此 Ve 的能力。这个最终测量值是最大自主通气量（MVV）。为了获得 MVV，指导患者尽可能用力呼吸 10 或 12 秒，并将所得体积乘以得到理论分钟体积。这不仅考验力学和肌肉力量，还考验理解力和合作性，这些因素也会影响脱机成功。

TRADITIONAL VENTILATOR WEANING
传统呼吸机脱机

Rationale 理由

With this weaning technique a prediction can be made that the patient no longer requires mechanical ventilatory support and the ventilator is withdrawn. If the patient is not considered able to breathe spontaneously for an unlimited period, short sojourns off the ventilator are initiated, with rest periods between, during which full ventilatory support is again provided. This technique of weaning was the first to be used and is still the standard against which newer methods are compared.
通过这种脱机技术，可以预测患者不再需要机械通气支持，并且会撤出呼吸机。如果认为患者不能无限期地自主呼吸，则开始短暂离开呼吸机，中间有休息时间，在此期间再次提供全面的通气支持。这种脱机技术是最早使用的，并且仍然是比较新方法的标准。

Picking the Right Time 选择合适的时间

Premature attempts at ventilator weaning and complications resulting from withdrawing support too soon can be minimized if the patient is otherwise stable and the underlying cause for acute respiratory failure has resolved or substantially improved. If significant deterioration has occurred in other organ systems-acute upper gastrointestinal bleeding or renal failure, for exampleventilator weaning may have to be delayed until these processes resolve or improve.
如果患者其他方面情况稳定，并且急性呼吸衰竭的根本原因已解决或显著改善，则可以最大限度地减少过早尝试撤机和过早撤出支持导致的并发症。如果其他器官系统发生显著恶化 - 例如急性上消化道出血或肾功能衰竭，则可能需要延迟脱机，直到这些过程消退或改善。

Technique 技术

Prediction of Success. Table 15-1 gives a protocol for successful weaning by the traditional method. It may be used with either AMV or IMV as the baseline ventilatory support mode. Using predetermined objective measurements for judging readiness to be weaned as compared with simply deciding to proceed on clinical grounds will improve success rates. Which objective measuremical grou which numerical criteria are employed may be less and which nume of the same technique with be crucial than
成功预测。表 15-1 给出了通过传统方法成功脱机的方案。它可以与 AMV 或 IMV 一起使用作为基线通气支持模式。与简单地根据临床原因决定进行相比，使用预定的客观测量来判断脱机准备情况将提高成功率。采用哪些客观测量 grou 哪些数字标准可能更少，哪些相同技术的数量至关重要
the consistent use ould weaning partient.
始终使用 Ould 断奶参与者。
The most helpful weaning parameters are listed under objective criteria in Table 15-1. A Ve requirement during mechanical ventilation (delivered by the ventilator, or by the ventilator plus spontaneous breaths in the case of IMV) that is less than 10 or 12

L / \min

-or twice the patient’s predicted normal resting VE-indicates that the demand placed on the patient for sustained spontaneous breathing will not be too great. A VC of at least

10 ml / kg

may be more useful than measurement of VT, at least following
最有用的脱机参数列在表 15-1 的客观标准下。机械通气期间的 Ve 需求（由呼吸机提供，或在 IMV 的情况下由呼吸机加自主呼吸提供）小于 10 或 12

L / \min

- 或患者预测的正常静息 VE 的两倍 - 表明对患者持续自主呼吸的需求不会太大。至少

10 ml / kg

VC 可能比 VT 测量更有用，至少在以下情况下

Table 15-1. TRADITIONAL WEANING PROTOCOL
表 15-1.传统脱机方案

Satisfy some predetermined objective criteria for initiating weaning.
满足一些预先确定的开始脱机的客观标准。
a. Respiratory failure improved.
一个。呼吸衰竭改善。
b. ${FIO}_{2}$ requirement 0.50 or less.
b. ${FIO}_{2}$ 要求 0.50 或更低。
c. Demand for ventilation manageable ( V e for normal ${PaCO}_{2}$ less than twice normal or $10 - 12 L / \min$ ).
c. 通气需求可控（正常 VE ${PaCO}_{2}$ 小于正常的两倍或 $10 - 12 L / \min$ ）。
d. Spontaneous ventilatory mechanics adequate.
d. 自主通气机制足够。
i. MIE least $- 20 cm H_{2} O$ . i. MIE 最少 $- 20 cm H_{2} O$ .
iii. MVV at least twice resting ${\dot{V}}_{E}$ requirement.
iii. MVV 至少两次休息 ${\dot{V}}_{E}$ 要求。
Choose the right time of day.
选择一天中的正确时间。
Eliminate or minimize sedation
消除或尽量减少镇静
Suction airway and position patient appropriately.
抽吸气道并适当地定位患者。
Switch to spontaneous ventilation (T-piece) at same ${FIO}_{2}$ with or without CPAP.
在有或没有 CPAP 的同时 ${FIO}_{2}$ 切换到自主通气（T 形件）。
Monitor patient closely. 密切监测患者。
a. Bedside observation/reassurance.
a. 床边观察/安抚。
b. Arterial blood gas measurement in $20 - 30 \min$ .
b.动脉血气测量 $20 - 30 \min$ 。

KEY:

{FIO}_{2} =

Fraction of inspired oxygen

{\dot{V}}_{E} =

Minute ventilation,

{PaCO}_{2} =

Arterial cart dioxide tension,

V C =

Vital capacity. MIF

=

Maximum inspiratory force. MVV

=

Maximum voluntary ventilation,

CPAP =

Continuous positive airway pressure. force.

MV =

Maximum
关键：

{FIO}_{2} =

吸入氧

{\dot{V}}_{E} =

分数分钟通气，

{PaCO}_{2} =

动脉二氧化分压，

V C =

肺活量。MIF

=

最大吸气力。MVV

=

最大自主通气，

CPAP =

持续气道正压通气。力。

MV =

最大
short-term ventilation (up to three to four days), and measurement of spontaneous respiratory rate (f) while the patient is momentarily off the ventilator may not be a consistently reliable predictor of weaning. An MIF of more than

- 20 cm H_{2} O

indicates adequate inspiratory muscle strength. The ability to double the required resting Ve during the MVV maneuver indicates sufficient ventilatory reserve to compensate for a moderate increase in demand, should this occur.
短期通气（最多 3 到 4 天）和患者暂时离开呼吸机时测量自主呼吸频率（F）可能不是脱机的持续可靠预测指标。MIF 大于

- 20 cm H_{2} O

表示足够的吸气肌力量。在 MVV 机动期间能够将所需的静息 Ve 加倍的能力表明，如果发生这种情况，有足够的通气储备来补偿需求的适度增加。

Time of Day. Several factors in addition to measurements of ventilatory function are important in successful weaning. The weaning attempt should be made at a time when staffing is maximal and other activities will not interfere. If possible, weaning attempts should be made during the day shift, and initiation of weaning at night should be avoided. The patient should not be involved in other activities, such as bathing, eating, or visiting with relatives, when the weaning attempt is made. If bronchodilator drugs are being used, the attempt should be timed so that their effects are maximal. Drugs that depress ventilation, such as narcotics and sedatives, should be withheld or cut back as much as possible. Just prior to taking the patient off the ventilator, the airway should be cleared using the techniques described in Chapter 9, and if possible the patient should be in the sitting or semiupright position, unless he or she is quadriplegic, in which case the diaphragm may function better with the patient supine.
Time of Day（当日时间）。除了通气功能的测量外，还有几个因素对成功脱机很重要。断奶尝试应在人员配备最大且其他活动不会干扰的时候进行。如果可能，应在白班期间尝试脱机，并避免在夜间开始脱机。尝试脱机时，患者不应参与其他活动，例如洗澡、进食或探亲。如果正在使用支气管扩张剂药物，应安排尝试时间，以便其效果最大。应尽可能停用或减少抑制通气的药物，例如麻醉剂和镇静剂。在将患者从呼吸机上取下之前，应使用第 9 章中描述的技术清理气道，如果可能，患者应处于坐位或半直立位，除非他或她四肢瘫痪，在这种情况下，横膈膜在患者仰卧时可能会功能更好。

Equipment Set-up and Personnel. Traditional weaning is accomplished by switching the patient from the ventilator circuit to a Tpiece, through which humidified gas at the same

{FIO}_{2}

flows at a rate sufficient to prevent rebreathing. An extension tube should be added to the expiratory side of the T-piece to prevent entrainment of room air, which can both lower the

{FIO}_{2}

and dry the airway. Some clinicians add continuous positive airway pressure (CPAP) at levels of

5 cm H_{2} O

, although the need for this approach has not been demonstrated in all patients. The transition from ventilator to spontaneous breathing should be preceded by careful explanation to the patient of what is to be done and why, along with the assurance that the person performing the weaning will remain with the patient or be immediately available. Calm reassurance by and the physical presence of physician, nurse, or respiratory therapist at the bedside during weaning prevents much patient agitation and distress that can result in abortion of the attempt.
设备设置和人员。传统的脱机是通过将患者从呼吸机回路切换到 T 件来完成的，相同的

{FIO}_{2}

湿化气体以足以防止再次呼吸的速度流过。应在 T 形件的呼气侧添加一根延长管，以防止室内空气夹带，这既可以降低

{FIO}_{2}

气道，也可以使气道干燥。一些临床医生在水平

5 cm H_{2} O

上添加持续气道正压通气（CPAP），但尚未在所有患者中证明这种方法的必要性。从呼吸机过渡到自主呼吸之前，应向患者仔细解释要做什么和原因，并保证进行脱机的人员会留在患者身边或立即可用。脱机时，医生、护士或呼吸治疗师在床旁的安抚和身体在场，可以防止患者过多的激越和痛苦，从而导致尝试流产。

Expected Physiological Changes. The weaning attempt should be followed by arterial blood gas measurement after 20 to 30 minutes, with success or failure determined according to the results. Mild distress and agitation can usually be managed by calmly reassuring the patient. More severe discomfort, which is more frequent the longer the patient has been ventilated prior to the weaning attempt,
预期的生理变化。脱机尝试后应在 20 至 30 分钟后进行动脉血气测量，根据结果确定成功或失败。轻度痛苦和激越通常可以通过冷静地安抚患者来控制。更严重的不适，患者在尝试脱机前通气的时间越长，不适就越频繁，
cal ventilation may metry reinstitution of mech awaited.
等待 Cal Ventilation May metry reinstitution of mech。
Arterial carbon arterial blood gas analysis are awaited.
正在等待动脉碳素动脉血气分析。
Arterial carbon dioxide tension

({PaCO}_{2})

often rises and arterial oxygen tension

({PaO}_{2})

falls during a trial of spontaneous ventilation; that the

{PaO}_{2}

falls somewhat less in many patients receiving CPAP is a major rationale for its use. So long as arterial pH remains above 7.30 and arterial hemoglobin saturation ( SaO ) is above 90 per cent, spontaneous breathing with or without CPAP may be continued while the trend of these changes is asse serial measurements. The Passessed with serial measurements. The

{PaCO}_{2}

and

{PaO}_{2}

usually stabilize within a short time with continued spontaneous ventilation.
在尝试自主通气期间，动脉二氧化碳分压

({PaCO}_{2})

经常升高，而动脉血氧分压

({PaO}_{2})

下降;许多接受 CPAP 的患者

{PaO}_{2}

跌倒率略低，这是使用其主要理由。只要动脉 pH 值保持在 7.30 以上且动脉血红蛋白饱和度（SaO）高于 90%，就可以继续有或没有 CPAP 的自主呼吸，而这些变化的趋势是评估连续测量。通过连续测量进行预评估。和

{PaCO}_{2}

{PaO}_{2}

通常在短时间内稳定下来，并持续自主通气。

Gradual Traditional Weaning
渐进式传统断奶

Most patients ventilated for a few days or less can simply be disconnected from the ventilator once they meet the criteria discussed earlier, but others wean more successfully over a period of hours using alternating periods of assisted and spontaneous ventilation (see Fig. 15-1B). The intervals of spontaneous breathing via a T-piece are progressively lengthened until the patient is independent of the ventilator for one to several he patient is ine that, in some pateral hours at a time. Clinical experience shows that, in some patients who have been ventilated for many days, gradual weaning during the day with return to full ventilatory support during the night may be more successful than abrupt weaning. Some patients receiving long-term ventilatory support are able to be independent of the ventilat throughout their throughout their waking hours, but maintain better health if they are returned to the ventilator at night.
大多数通气几天或更短时间的患者在满足前面讨论的标准后可以简单地断开呼吸机，但其他患者使用交替的辅助通气和自主通气在几个小时内脱机更成功（见图 15-1B）。通过 T 形件进行自主呼吸的间隔逐渐延长，直到患者在一到几个小时内独立于呼吸机，一次在一些父系小时内。临床经验表明，在一些已经通气多天的患者中，白天逐渐脱机，夜间恢复完全通气支持可能比突然脱机更成功。一些接受长期通气支持的患者能够在清醒的整个时间内独立于呼吸机，但如果他们在晚上回到呼吸机上，则可以保持更好的健康状况。

WEANING WITH INTERMITTENT MANDATORY VENTILATION
间歇性指令通气脱机

Rationale 理由

Intermittent mandatory ventilation was originally introduced as a weaning technique, although it is now also used as a primary mode of ventilatory support. As a weaning technique, IMV allows mechanical ventilation to be withdrawn gradually rather than abruptly. In addition, rather than relying on prediction of success prior to attempting weaning, with IMV weaning is begun empirically and allowed to proceed as far as possible using blood gas results as the major measure of success.
间歇性指令通气最初是作为一种脱机技术引入的，尽管它现在也被用作通气支持的主要模式。作为一种脱机技术，IMV 允许逐渐而不是突然退出机械通气。此外，IMV 脱机不是依赖于尝试脱机前对成功的预测，而是根据经验开始脱机，并允许尽可能使用血气结果作为成功的主要衡量标准进行。

Picking the Right Time 选择合适的时间

Successful weaning with IMV requires adherence to the same principles discussed earlier under traditional weaning.
IMV 成功脱机需要遵守前面在传统脱机下讨论的相同原则。

Technique 技术

Weaning with IMV consists of repeating a two-step sequence until the ventilator rate is reduced to zero and the patient breathes
IMV 脱机包括重复两步序列，直到呼吸机频率降至零并且患者呼吸
without assistance. The machine rate is reduced, usually by one or two breaths

/ \min

, and arterial blood gas values are measured after 20 to 30 minutes. So long as the pH does not fall below a predetermined cut-off value-usually 7.30 or 7.35 -these steps are repeated. Used in weaning as originally intended, IMV permits most patients to be completely off the ventilator within a few hours, as shown in Figure 15-1C. This technique is commonly misused, however, with only one or two rate reductions per day, a regimen that increases total ventilator time (and cost) in comparison with traditional weaning. Used properly, weaning with IMV after short-term ventilatory support takes about the same amount of time as traditional weaning, although it may require more ventilator adjustments and thus more blood gas measurements.
没有帮助。机器频率降低，通常减少

/ \min

1 次或 2 次呼吸，并在 20 至 30 分钟后测量动脉血气值。只要 pH 值不低于预定的临界值（通常为 7.30 或 7.35），就会重复这些步骤。IMV 按最初预期用于脱机，允许大多数患者在几个小时内完全脱离呼吸机，如图 15-1C 所示。然而，这种技术经常被误用，每天只降低一到两次速率，与传统脱机相比，这种方案增加了呼吸机的总时间（和成本）。如果使用得当，短期通气支持后使用 IMV 脱机所需的时间与传统脱机大致相同，尽管它可能需要更多的呼吸机调整，因此需要更多的血气测量。

Gradual IMV Weaning 渐进式 IMV 脱机

With this technique the ventilator rate is reduced more slowly and mechanical support is withdrawn over a period of days rather than hours. Although unnecessary in most patients with short-term mechanical ventilation, this regimen may be helpful in some individuals who have required prolonged ventilation prior to the weaning attempt, and perhaps in those who fail attempts at gradual traditional weaning, especially at night. Any intrinsic advantage of one weaning method over another is probably insignificant, provided the basic principles of respiratory care are followed. Whether traditional or IMV weaning is used is more a matter of individual preference than of any inherent superiority of either technique.
使用这种技术，呼吸机频率降低得更慢，机械支持在几天而不是几小时内撤出。虽然对于大多数短期机械通气的患者来说没有必要，但这种方案可能对一些在脱机前需要长时间通气的个体有帮助，也可能对那些尝试逐渐传统脱机失败的患者有帮助，尤其是在夜间。只要遵循呼吸护理的基本原则，一种脱机方法相对于另一种脱机方法的任何内在优势可能都是微不足道的。是否使用传统或 IMV 脱机更多地是个人偏好的问题，而不是任何一种技术的固有优势。

WEANING WITH PRESSURE SUPPORT
使用压力支持脱机

Rationale 理由

With the current generation of ICU ventilators, peak inspiratory flow rates during patient-initiated breaths tend to be higher but at lower peak pressures with PSV than with AMV or IMV. The inspiratory pressure-wave form during PSV is more comfortable for many dyspneic patients than that delivered with the other modes. Use of PSV focuses on reducing the patient’s overall work of breathing, and on eliminating the added (imposed) work of breathing that rube and ventilator circuit.
使用最新一代的 ICU 呼吸机，PSV 在患者发起呼吸期间的峰值吸气流速往往高于 AMV 或 IMV，但峰值压力较低。PSV 期间的吸气压力波形式对许多呼吸困难患者来说比其他模式更舒适。PSV 的使用侧重于减少患者的整体呼吸功，并消除呼吸循环和呼吸回路的额外（强加）功。

Picking the Right Time 选择合适的时间

This in general is the same as with T-piece and IMV weaning, as discussed above.
这通常与如上所述的 T 型和 IMV 脱机相同。

Technique 技术

With PSV as a stand-alone weaning technique, the patient is switched from volume-limited ventilation (AMV or IMV) to PSV at a level sufficient to provide the same VT (e.g., 10 to

12 ml / kg

). The inspiratory pressure support level is then progressively reduced, monitoring primarily the patient’s spontaneous respiratory rate as an indicator of the adequacy of support. So long as the rate remains below 30 breaths

/ \min

the pressure is sequentially lowered until it is only 5 to

10 cm H_{2} O

, at which point the patient is extubated (assuming there is no other indication for an artificial airway-see Chapter 8). As with the other weaning techniques, arterial blood gas analysis should usually be carried out prior to extubation-to confirm the success of the weaning protocol, remembering that hypoxemia and/or acute respiratory acidosis cannot reliably be detected without such analysis.
将 PSV 作为一种独立的脱机技术，患者从容量限制通气（AMV 或 IMV）切换到足以提供相同 VT 的水平（例如，10 至

12 ml / kg

）的 PSV。然后逐渐降低吸气压力支持水平，主要监测患者的自主呼吸频率，作为支持是否充分的指标。只要呼吸频率保持在 30 次以下，

/ \min

压力就会依次降低，直到只有 5 到

10 cm H_{2} O

，此时患者被拔管（假设没有人工气道的其他适应症 - 见第 8 章）。与其他脱机技术一样，动脉血气分析通常应在拔管前进行 - 以确认脱机方案的成功，请记住，如果不进行此类分析，就无法可靠地检测到低氧血症和/或急性呼吸性酸中毒。

FAILURE TO WEAN 脱机失败

Definition 定义

The patient who cannot be removed from mechanical ventilatory support despite application of the principles discussed in this chapter may be said to have failed a weaning attempt. The most frequent manifestation of this failure is acute respiratory acidosis, an increase in

{PaCO}_{2}

to the degree that pH falls to 7.30 or less. Patients can also fail to be weaned because of uncontrollable agitation and respiratory distress despite correct use of equipment and technique. If gas exchange is adequate, this is usually controllable with reassurance and gentle sedation. It should be emphasized that most instances of apparent “failure” in weaning are due to neglect of one or more of the basics, either in treatment of the underlying problem or in preparation of the patient for weaning.
尽管应用了本章讨论的原则，但仍无法脱离机械通气支持的患者，可以说是脱机尝试失败。这种失败最常见的表现是急性呼吸性酸中毒，即 pH 值下降

{PaCO}_{2}

到 7.30 或更低的程度。尽管正确使用设备和技术，患者也可能因为无法控制的激越和呼吸窘迫而无法脱机。如果气体交换充分，通常可以通过安抚和温和镇静来控制。应该强调的是，大多数脱机明显 “失败 ”的情况是由于忽视了一项或多项基本知识，无论是在治疗潜在问题时，还是在为病人脱机做准备时。

Weakness 弱点

Patients whose VC is less than

10 ml / kg

or whose MIF is less than

- 20 cm H_{2} O

on preweaning assessment are unable to keep up with ventilatory needs even if these are normal. The following causes should be sought.
断奶前评估

- 20 cm H_{2} O

中 VC 小于

10 ml / kg

或 MIF 小于 MIF 的患者无法满足通气需求，即使这些需求是正常的。应寻找以下原因。

Drugs. Aminoglycoside antibiotics such as polymyxin, streptomycin, or gentamycin can produce neuromuscular blockade soon after the drug is given in very large amounts, particularly if instilled in the peritoneum. Weaning should not be attempted for patients who have received neuromuscular blocking agents such as pancuronium bromide (Pavulon) or curare until all effects of the drug have disappeared.
药物。氨基糖苷类抗生素（如多粘菌素、链霉素或庆大霉素）在大量给药后不久即可产生神经肌肉阻滞，特别是滴入腹膜时。对于已接受神经肌肉阻滞剂（如泮库溴铵（Pavulon）或箭毒）的患者，在药物的所有作用消失之前，不应尝试脱机。

Metabolic Abnormalities. Hypophosphatemia, hypomagnesemia, and hypokalemia can cause failure to wean because of muscular weakness. These conditions should be suspected in all patients who fail to wean because of weakness. Hypothyroidism is another potential contributor, although it is difficult to diagnose accurately in critically ill patients.
代谢异常。低磷血症、低镁血症和低钾血症可因肌肉无力而导致脱机失败。所有因虚弱而未能脱机的患者都应怀疑这些情况。甲状腺功能减退症是另一个潜在的促成因素，尽管在危重患者中很难准确诊断。
Malnutrition. Protein-calorie malnutrition in patients who have been seriously ill for weeks can produce neuromuscular weakness that interferes with weaning, although the mechanisms are unclear and this problem is difficult to document objectively. In poorly nourished patients, successful weaning sometimes becomes possible after a period of intensive nutritional repletion in conjunction with correction of metabolic and electrolyte abnormalities.
营养不良。重病数周的患者的蛋白质热量营养不良会导致神经肌肉无力，从而干扰脱机，但机制尚不清楚，而且这个问题很难客观记录。对于营养不良的患者，经过一段时间的强化营养补充并纠正代谢和电解质异常后，有时可以成功脱机。
Primary Neuromuscular Disease. Conditions such as multiple sclerosis and myasthenia gravis are usually evident prior to the onset of acute respiratory failure. This cause for failure to wean is hard to document and must usually be diagnosed by exclusion of other processes. Respiratory muscle dysfunction is discussed further in Chapter 5.
原发性神经肌肉疾病。多发性硬化症和重症肌无力等疾病通常在急性呼吸衰竭发作之前就很明显。这种脱机失败的原因很难记录，通常必须通过排除其他过程来诊断。呼吸肌功能障碍将在第 5 章中进一步讨论。

Insufficient Ventilatory Drive
通气驱动不足

Respiratory Alkalosis. This is the most common cause of the failure of a patient to breathe spontaneously when disconnected from a ventilator. Especially when AMV is used, dyspneic patients may establish an acute respiratory alkalosis that effectively suppresses their drive to breathe until hypoxemia or hypercapnia intervenes. In patients with normal

\dot{V} {CO}_{2}, PaCO

, rises 8 to 10 mmHg during the first minute of apnea and about 3 mmHg per With severe respiratory alkalosis, it may thus minute thereater. before

{PaCO}_{2}

rises to the usual apneic threshus take several minu mmHg when no metabolic component is presully 36 to 38 respiratory alkalosis should be corrected prior to initial weaning
呼吸性碱中毒。这是患者在断开呼吸机时无法自主呼吸的最常见原因。特别是当使用 AMV 时，呼吸困难患者可能会形成急性呼吸性碱中毒，从而有效抑制他们的呼吸动力，直到低氧血症或高碳酸血症介入。在正常

\dot{V} {CO}_{2}, PaCO

患者中，在呼吸暂停的第一分钟内升高 8 至 10 mmHg，每严重呼吸性碱中毒时升高约 3 mmHg，因此可能会更轻微。在上升到正常的呼吸暂停阈值之前

{PaCO}_{2}

，当没有代谢成分时，服用几个 minu mmHg，36 至 38 呼吸性碱中毒应在初始脱机前纠正
Metabolic Alkalosis. As discussed in Chapter 4, metabolic alkalosis commonly results from diuretic-induced renal potassium and chloride depletion and from losses of hydrogen ion and electrolytes from the gastrointestinal tract, both of which are common in ventilated patients. The combination of metabolic and respiratory alkalosis is particularly troublesome in preventing successful weaning in many patients. These abnormalities should be corrected before another weaning attempt is made. Elimination of nasogastric suction loss and administration of potassium chloride to correct hypokalemic alkalosis are the most important measures here.
代谢性碱中毒。如第 4 章所述，代谢性碱中毒通常是由利尿剂诱导的肾钾和氯化物耗竭以及胃肠道氢离子和电解质流失引起的，这两者都在通气患者中很常见。代谢性碱中毒和呼吸性碱中毒的结合在阻止许多患者成功脱机方面特别麻烦。在再次尝试脱机之前，应纠正这些异常。消除鼻胃管抽吸损失和给予氯化钾以纠正低钾性碱中毒是最重要的措施。
Drugs. Patients receiving narcotic analgesics and large doses of sedative drugs may fail a weaning attempt because of suppression
药物。接受麻醉镇痛药和大剂量镇静药的患者可能会因抑制而无法尝试脱机
of their ventilatory drives by these agents. Careful review of the medication sheets of patients who are difficult to wean often reveals administration of several drugs that could suppress ventilation; frequently these have been continued inadvertently even though they are no longer needed. In any case, such drugs should be discontinued or substantially cut back before another weaning attempt is made.
这些药物对他们的通气驱动。仔细审查难以脱机的患者的药物表通常会发现服用几种可能抑制通气的药物;这些经常在不经意间继续进行，即使它们不再需要。在任何情况下，在再次尝试脱机之前，应停用或大幅减少此类药物。

Other Causes. Malnutrition depresses endogenous ventilatory drives in addition to weakening the respiratory muscles. Myxedema also depresses ventilatory drives. Occasionally patients with cerebrovascular accidents or congenital abnormalities may lack hypoxic or hypercapnic sensitivity or even central respiratory drive, although such occurrences as causes of weaning failure are rare. Administration of respiratory stimulant drugs such as doxapram (Dopram) or medroxyprogesterone acetate (Provera) seldom allows an otherwise unweanable patient to become completely ven-tilator-independent, and weaning in cases of insufficient drive requires correction of the underlying problem, if this can be accomplished.
其他原因。营养不良除了削弱呼吸肌外，还会抑制内源性通气驱动。粘液性水肿还会抑制通气驱动。偶尔，脑血管意外或先天性异常的患者可能缺乏低氧或高碳酸血症敏感性，甚至缺乏中枢呼吸驱动，尽管作为脱机失败原因的情况很少见。使用呼吸兴奋剂药物，如多沙普兰（Dopram）或醋酸甲羟孕酮（Provera），很少能使原本无法断奶的患者完全独立，在驱动力不足的情况下脱机需要纠正潜在问题，如果可以做到这一点。

Excessive Work of Breathing
过度呼吸功

Small or Obstructed Endotracheal Tube. Some patients who are unable to sustain spontaneous ventilation through an endotracheal tube are capable of breathing on their own when extubated. The resistance to flow through a tube, and hence the work required to overcome it, varies with the length of the tube and also inversely with the fourth power of the tube’s smallest effective radius. At a flow rate of

1 L / \sec

the resistance to flow through an endotracheal tube with an inside diameter of 9 mm is

0.6 cm H_{2} O

; for an

8 - mm

tube, it is

1.9 cm H_{2} O

. For a

7 - mm

tube the resistance increases to

4.0 cm H_{2} O

, and it is even greater for smaller tubes. This radius effect applies to the tube’s narrowest point, so that a kinked tube or one partly clogged by mucus has a smaller effective radius and much greater resistance than its caliber would suggest. Prolonged spontaneous ventilation through a 6 - or

7 - mm

endotracheal tube may be beyond the capability of the patient, especially if the required Ve is more than 10 or 12 L . For patients who are alert and who can be expected to protect their airways from aspiration, ventilator weaning and extubation can sometimes be accomplished simultaneously. If this cannot be done, the endotracheal tube should be exchanged for one at least 1 mm larger before spontaneous ventilation through a T-piece can be reattempted.
气管插管小或阻塞。一些无法通过气管插管维持自主通气的患者在拔管时能够自行呼吸。流经管子的阻力，以及克服它所需的功，随管子的长度而变化，也与管子最小有效半径的四次方成反比。在流速下

1 L / \sec

，流经内径为 9 mm 的气管插管的阻力为

0.6 cm H_{2} O

;对于管子

8 - mm

，它是

1.9 cm H_{2} O

。对于

7 - mm

管子，电阻增加到

4.0 cm H_{2} O

，对于较小的管子，电阻甚至更大。这种半径效应适用于管子的最窄点，因此扭结的管子或部分被粘液堵塞的管子具有比其口径所暗示的更小的有效半径和更大的阻力。通过 6 或气

7 - mm

管插管进行长时间自主通气可能超出患者的能力，特别是当所需的 Ve 超过 10 或 12 L 时。对于警觉且可以保护气道免受误吸的患者，有时可以同时完成呼吸机脱机和拔管。如果无法做到这一点，则应将气管插管更换为至少 1 mm 大的插管，然后才能再次尝试通过 T 形导管进行自主通气。

Pressure support can be added to compensate for the work of breathing imposed by the tube. For endotracheal tubes of 7.0 mm or greater inside diameter and VE requirements up to about

12 L /

min, 5 cm H_{2} O

is sufficient. If the tube is less than 70 mm or the
可以添加压力支持以补偿管子施加的呼吸功。对于内径为 7.0 毫米或更大的气管插管和 VE 要求就

12 L /

min, 5 cm H_{2} O

足够了。如果管子小于 70 mm 或

Ve 12 to

16 L / \min

, 8 to

10 cm H_{2} O

of pressure support should be used.
应使用 Ve 12 至

16 L / \min

， 8 至

10 cm H_{2} O

的压力支持。

High-Resistance Pathway for Spontaneous Breathing. Because different ventilators and tubing circuits have different resistances, it is important to examine the circuit through which a patient is required to breathe spontaneously during weaning. Depending on the physical arrangement of the valves and tubing, and also on the degree of pressurization of the circuit, the effort put forth by the patient to draw spontaneous breaths may be excessive and prevent successful weaning. This consideration is technical but can be crucially important: Breathing through a ventilator circuit at a machine rate of zero may require considerably more work than breathing through a T-piece, and familiarity with the circuitry in use is essential.
自主呼吸的高阻力通路。由于不同的呼吸机和管道回路具有不同的阻力，因此检查患者在脱机期间需要自主呼吸的回路非常重要。根据瓣膜和管道的物理布置，以及回路的压力程度，患者吸气的努力可能会过大，从而阻止成功脱机。这种考虑是技术性的，但可能至关重要：与通过 T 形件呼吸相比，通过呼吸机回路呼吸可能需要更多的工作，并且熟悉正在使用的回路是必不可少的。

Airway Obstruction. Patients with bronchospasm, thick secretions, or foreign bodies in the major airways should have these reversed or removed prior to another weaning attempt, as discussed under Traditional Ventilator Weaning.
气道阻塞。支气管痉挛、主要气道有浓稠分泌物或异物的患者，在再次尝试脱机之前，应将其倒转或取出，如传统呼吸机脱机中所述。

Chest Restriction. The patient whose chest excursion is limited by bandages or restraints may be unable to be weaned until these are removed or loosened. Very obese patients or those with postoperative bowel distention may not be weaned successfully if they cannot or will not sit up.
胸部限制。如果患者的胸部活动受到绷带或约束装置的限制，则在移除或松开绷带或约束装置之前，可能无法脱机。非常肥胖的患者或术后肠胀的患者如果不能或不愿坐起来，可能无法成功脱机。

Pain. Postoperative or postresuscitation pain can prevent weaning by causing patients to breathe rapidly and shallowly. Local or regional anesthesia may be more effective in such patients than systemic analgesia.
疼痛。术后或复苏后疼痛可通过导致患者呼吸急促和浅浅来阻止脱机。对于此类患者，局部或区域麻醉可能比全身镇痛更有效。

Anxiety. Excessively anxious or agitated patients often cannot be weaned until they can be calmed. If this cannot be accomplished without heavy sedation or paralysis, weaning will have to be deferred until the cause of the agitation can be removed.
焦虑。过度焦虑或激动的患者通常无法脱机，直到他们能够平静下来。如果不使用大量镇静剂或麻痹就无法完成此作，则必须推迟脱机，直到可以消除激越的原因。

High Ve Requirement 高 Ve 要求

High

{V C O}_{2}

. Ongoing sepsis, inflammation, and occasionally excessive hyperalimentation can increase the demand for ventilation to such an extent that the patient cannot keep up without mechanical assistance. This problem can be assessed easily by collecting expired gas for three minutes in a Douglas bag and analyzing it for

{CO}_{2}

on a blood gas machine, permitting calculation of

\dot{VCO} {CO}_{2}

in milliliters per minute. This technique works with both AMV and IMV; with the latter the collected volume is larger, but the

{CO}_{2}

produced will be the same. Carbon dioxide volume greater than
高

{V C O}_{2}

.持续的脓毒症、炎症和偶尔的过量营养会增加对通气的需求，以至于患者在没有机械帮助的情况下无法跟上。通过将呼出的气体收集在道格拉斯袋中三分钟，然后在血气机上进行分析

{CO}_{2}

，可以每分钟毫升数计算

\dot{VCO} {CO}_{2}

，从而轻松评估这个问题。该技术适用于 AMV 和 IMV;对于后者，收集的体积更大，但

{CO}_{2}

产生的体积是相同的。二氧化碳体积大于
the 200 to

250 ml / \min

expected in a normal-sized adult confirms the presence of excessive ventilatory demand due to high

{VCO}_{2}

. When this is the case, attention should be given to correcting this excess before another weaning attempt is made.
正常体型的成年人预期的 200

250 ml / \min

证实了由于高

{VCO}_{2}

.在这种情况下，应注意在再次尝试脱机之前纠正这种超额。

High Vd/Vt. Patients with severe ARDS typically have high physiological dead space ventilation, and this can persist well into the phase of clinical recovery. Severe COPD, status asthmaticus, and multiple pulmonary thromboemboli are also characterized by high Vd/Vt. The Vd/Vt can be measured at the same time that

{VCO}_{2}

is determined if an arterial blood gas analysis is done concurrently. VD/VT is calculated according to the following formula:
重度 ARDS 患者通常具有高生理死腔通气，并且可以很好地持续到临床恢复阶段。重度 COPD、哮喘持续状态和多发性肺血栓栓塞也以高 Vd/Vt 为特征。Vd/Vt 可以在确定动脉血气分析的同时进行

{VCO}_{2}

测量。VD/VT 根据以下公式计算：

Vd / VT = \frac{{PaCO}_{2} - {PECO}_{2}}{{PaCO}_{2}}

where

{PECO}_{2}

is the

{PCO}_{2}

in the mixed expired gas. A value for Vd/Vt exceeding 0.50 during mechanical ventilation is high, and patients usually cannot be weaned if the value exceeds 0.60 .
其中

{PECO}_{2}

是

{PCO}_{2}

混合过期气体。机械通气期间 Vd/Vt 值超过 0.50 很高，如果该值超过 0.60，患者通常无法脱机。

If high Vd/VT is documented in a patient being considered for weaning, efforts should be made to improve the condition causing the abnormality. In resolving ARDS it is often necessary to wait several days and monitor VD/VT and

\dot{V} C O_{2}

values repeatedly before reattempting weaning.
如果考虑脱机的患者记录到高 Vd/VT，则应努力改善导致异常的状况。在解决 ARDS 时，通常需要等待数天并反复监测 VD/VT 和

\dot{V} C O_{2}

值，然后再尝试脱机。

WEANING FROM ENDOTRACHEAL INTUBATION
气管插管脱机

DEFINITION 定义

The discontinuation of upper airway bypass by orotracheal, nasotracheal, or tracheostomy tube may be considered weaning in a sense analogous to the use of the word to describe the discontinuation of mechanical ventilation. As discussed in Chapter 8, this discontinuation can be either abrupt, as in the majority of patients when the tube is simply removed, or gradual, when transitional plugging or substitution of a button is used.
通过经口气管、鼻缝合或气管切开插管停止上气道旁路手术可被视为脱机，其意义类似于使用该词来描述机械通气的停止。如第 8 章所述，这种停药可以是突然的，就像在大多数患者中简单地拔除管子一样，也可以是逐渐的，当使用过渡性堵塞或替代按钮时。

PREDICTORS OF SUCCESS 成功的预测因素

Unlike ventilator weaning, no objectively defined parameters exist to predict successful endotracheal extubation other than those assessing postextubation cough ability (see Chapter 9). No studies
与呼吸机脱机不同，除了评估拔管后咳嗽能力的参数外，没有客观定义的参数可以预测气管插管成功（见第 9 章）。无研究
to date have examined the value of assessments made prior to removal in assuring that reintubation will not be required. Clinical experience shows, however, that recalling the indications for endotracheal intubation can help when assessing patients for extubation. The main reasons artificial airways are inserted are:
迄今为止，已经检查了拔除前所做的评估的价值，以确保不需要重新插管。然而，临床经验表明，回顾气管插管的适应证有助于评估患者是否拔管。插入人工气道的主要原因是：
a. to prevent or reverse upper airway restriction.
A. 防止或逆转上气道受限。
b. to protect the lower respiratory tract from aspiration of gastric or mouth contents.
b. 保护下呼吸道不吸入胃或口腔内容物。
c. to facilitate the removal of secretions.
c. 促进分泌物的排出。
d. to provide a closed system for mechanical ventilation.
d. 为机械通风提供一个封闭的系统。

Once a patient has been weaned from mechanical ventilation, the last of these indications no longer applies, although it is occasionally useful to leave patients intubated for another day when the success of ventilator weaning of more than several hours is uncertain. The need to protect the airway against aspiration is harder to assess. The usual procedure is to stroke the posterior pharynx with a tongue depressor to see if the patient gags, although this test has neither been standardized nor studied for its protective value once the patient is extubated.’ Unless a discrete bulbar neurological defect is present, however, patients who are alert and mobile can usually avoid aspiration. In individuals with impaired mental status or in patients who are immobilized by disease or treatment, no firm guidelines exist. For example, whether the patient with coma after head trauma or anoxia should remain intubated to protect the airway and to prevent pneumonia has never been investigated, and the decision must rest on the experience and preference of the clinician.
一旦患者脱离机械通气，这些适应证中的最后一种就不再适用，尽管当呼吸机脱机成功超过几个小时不确定时，让患者再插管一天有时是有用的。保护气道免受误吸的必要性更难评估。通常的程序是用压舌板抚摸咽后部，看看病人是否呕吐，尽管这种测试既没有标准化，也没有研究过病人拔管后的保护价值。然而，除非存在离散的延髓神经功能障碍，否则警觉且活动的患者通常可以避免误吸。对于精神状态受损的个体或因疾病或治疗而无法行动的患者，没有明确的指导方针。例如，颅脑外伤或缺氧后昏迷的患者是否应继续插管以保护气道和预防肺炎，从未研究过，必须根据临床医生的经验和偏好来决定。
When endotracheal intubation has been performed in order to facilitate the removal of secretions, extubation depends on the progress made in reversing this indication. Again, no objective measurable parameters exist other than for cough effectiveness, although it is reasonable to attempt extubation when there has been improyement in the chest roentgenogram, sputum culture, physical examination, or some other indicator of overall clinical improvement. Extubation in such instances is still an empirical trial, and the clinician must be prepared to reintubate if necessary.
当为了方便排出分泌物而进行气管插管时，拔管取决于逆转这一适应证的进展。同样，除了咳嗽效果外，不存在客观的可测量参数，尽管当胸部 X 线片、痰培养、体格检查或整体临床改善的其他指标出现不适时尝试拔管是合理的。在这种情况下，拔管仍然是一项经验性试验，临床医生必须准备好在必要时重新插管。

TECHNIQUE 技术

Technique and other aspects of airway care are discussed in Chapter 8.
第 8 章讨论了气道护理的技术和其他方面。

MONITORING THE PATIENT 监测患者

INTENSIVE CARE MONITORING
重症监护监测

WHAT TO MONITOR, AND WHY
要监控的内容和原因

Respiratory care monitoring is performed to supply appropriate and correct physiological information about patients and to measure the effects of therapy. In order to accomplish these goals, the clinician must decide, for each patient and often on multiple occasions in the course of an illness, what variables to measure and how to measure them. General guidelines for deciding on a given monitoring procedure are outlined in Table 16-1. Implicit in the guidelines are these questions:
进行呼吸护理监测是为了提供有关患者的适当和正确的生理信息并测量治疗效果。为了实现这些目标，临床医生必须为每位患者决定，并且通常在病程中的多个场合，决定要测量哪些变量以及如何测量它们。表 16-1 中概述了决定给定监视程序的一般准则。指南中隐含了以下问题：

Is the procedure needed? 是否需要该程序？
Is it safe? 安全吗？
Does it work? 它有效吗？
Is it cost effective? 成本效益高吗？
Are the data generated by the procedure accurate?
该程序生成的数据准确吗？
Will they be used? 它们会被使用吗？

MONITORING WITHOUT MACHINERY
无需机械即可进行监控

No collection of numbers on a computer printout can substitute for bedside skills. In addition to such objective measures as respiratory rate, heart rate, and blood pressure, a bedside observer can assess such intangibles as patient comfort and respiratory distress. The “appropriateness” of the patient-something that encompasses mental status, communication, and cooperativenesscan be an important indicator of physiological deterioration or improvement. Observation of the patient and rapid physical examination are crucial when electronic monitoring equipment signals an abrupt change, e.g., the quick separation of physiological catastrophe from equipment malfunction or artifact. In cases of sudden patient distress during mechanical ventilation, inspection 246.
计算机打印输出上的数字集合不能替代床边技能。除了呼吸频率、心率和血压等客观指标外，床边观察者还可以评估患者舒适度和呼吸窘迫等无形因素。患者的“适当性”——包括精神状态、沟通和合作性的东西可能是生理恶化或改善的重要指标。当电子监测设备发出突然变化的信号时，例如，将生理灾难与设备故障或伪影快速分离时，对患者的观察和快速体格检查至关重要。在机械通气期间患者突然感到痛苦的情况下，检查 246。

Table 16-1. CLINICAL CONSIDERATIONS IN THE USE OF A GIVEN MONITORING PROCEDURE OR MEASUREMENT
表 16-1.使用特定监测程序或测量的临床注意事项

Ease or difficulty of obtaining the measurement Invasiveness or patient risk in obtaining the measurement Precision and variability of the measurement technique Raseline physiological variability of the function being measured decisions in this patient
获得测量的难易程度或困难获得测量的侵入性或患者风险测量技术的精度和可变性 Raseline 被测功能的生理变异性该患者的决策
Cost of the measurement 测量成本
for chest symmetry and examination for hyperresonance can be life-saving when the cause is tension pneumothorax.
对于胸部对称性，当原因是张力性气胸时，检查高共振可以挽救生命。
Actual measurement of the work of breathing is not presently feasible for routine clinical application in seriously ill patients. However, visual estimation of minute ventilation (VE) and the respiratory muscle exertion needed to maintain it can be extremely helpful, particularly if serial estimations are made. Similarly, although direct measurement of peripheral tissue perfusion is unavailable, a careful assessment of skin color, turgor, and temperature, along with mental status and urine output, may provide essential information.
呼吸功的实际测量目前对于重症患者的常规临床应用是不可行的。然而，目测估计每分钟通气量（minute ventilation， VE）和维持它所需的呼吸肌用力可能非常有帮助，尤其是在进行连续估计的情况下。同样，虽然无法直接测量外周组织灌注，但仔细评估肤色、肿胀和体温，以及精神状态和尿量，可能提供重要信息。

Despite the value of bedside observation, this monitoring technique is limited by the clinican’s skills. In addition, even the most experienced clinician may be unable to evaluate the meaning of the presence or absence of certain signs. Central cyanosis (discussed in Chapter 6) is usually suggestive of hypoxemia if present. Nevertheless, cyanosis may be evident in some patients with normal arterial oxygenation, whereas others with significant hypoxemia may not be cyanotic. Similarly, studies have demonstrated that the adequacy of alveolar ventilation cannot be reliably estimated by bedside observation, as confirmed by arterial blood gas measurements.
尽管床旁观察很有价值，但这种监测技术受到临床医生技能的限制。此外，即使是最有经验的临床医生也可能无法评估某些体征的存在或缺失的意义。中心性紫绀（在第 6 章中讨论）如果存在，通常提示低氧血症。然而，一些动脉氧合正常的患者可能明显发绀，而其他严重低氧血症的患者可能没有紫绀。同样，研究表明，动脉血气测量证实，床旁观察无法可靠地估计肺泡通气的充分性。

THE CHEST ROENTGENOGRAM AS A MONITORING TOOL
胸部 X 线片作为监测工具

Portable chest roentgenograms are an important adjunct in noninvasive monitoring of patients in the intensive care unit (ICU). However, while this diagnostic procedure can aid management, it also has definite shortcomings. The chest roentgenogram is essential following certain invasive procedures (central venous line placement, thoracentesis, chest tube insertion) to detect complications and to confirm the results of the procedure. Pneumothorax comm common and potentially deadly complication of respiratory illness and its management, can often only be detected radiographically. In addition, the course of pneumonia or the adult respiratory distress syndrome (ARDS) can be followed by assessment of general trends over several days.
便携式胸部 X 线片是重症监护病房（ICU）患者无创监测的重要辅助手段。然而，虽然这种诊断程序可以帮助管理，但它也有明确的缺点。在某些侵入性手术（中心静脉导管放置、胸腔穿刺术、胸管插入）后，必须进行胸部 X 线检查，以检测并发症并确认手术结果。气胸是呼吸系统疾病的常见且可能致命的并发症及其管理，通常只能通过放射学检查发现。此外，肺炎或成人呼吸窘迫综合征（ARDS）的病程后，可以评估数日的总体趋势。

248 / MONITORING THE PATIENT
248 / 监测病人

On the other hand, the bedside portable chest roentgenogram is a poor monitoring tool in numerous respects. It is expensive, and there is a tendency to read too much into it. The technical differences between portable and routine roentgenograms, discussed in Chapter 6, make interpretation of heart size difficult on a portable examination. When portable roentgenograms are taken, the patient often cannot cooperate; bandages, orthopedic devices, or other apparatus may lie in the path of the exposure; and exposure distance is hard to keep constant in serial films. Consequently, subtle abnormalities are often missed, and film-to-film variation in the appearance of pulmonary infiltrates occurs. Also, bedside roentgenograms are static, not dynamic, reflecting a patient’s condition at only one moment in time. For these reasons, the portable roentgenogram should not be used to judge hour-bythe portail roug or to mour-byhour clinical progress or to make specific diagnoses. Rather; it should be used as an adjunct to bedside examination, keeping in mind its limitations.
另一方面，床边便携式胸部 X 线片在许多方面都是一种糟糕的监测工具。它很昂贵，而且往往会读得太多。第 6 章中讨论的便携式和常规 X 线片之间的技术差异使得便携式检查难以解释心脏大小。当进行便携式 X 线片检查时，患者通常无法配合;绷带、矫形器械或其他器具可能位于暴露路径上;而且在连续电影中很难保持曝光距离恒定。因此，经常会漏掉细微的异常，并且肺部浸润的外观会出现薄膜间差异。此外，床边 X 线片是静态的，而不是动态的，只反映患者在某一时刻的状况。由于这些原因，便携式 X 线片不应用于按小时判断 portail roug 或按小时哀悼临床进展或做出具体诊断。而;它应该用作床旁检查的辅助手段，同时牢记其局限性。

MONITORING VENTILATORY MECHANICS
监测通气力学

Respiratory Rate 呼吸频率

Spontaneous breathing frequency (f) in a patient with respiratory disease can be thought of as an index of respiratory mechanics. Counting

f

by visual observation is the main way this function is monitored. Respirations should be counted under comparable conditions for meaningful serial comparisons. Counting at times of external manipulation such as bathing, suctioning, and turning should be avoided. If spontaneous

f

is measured during a brief period off a mechanical ventilator, the interval should be the same, e.g., for 30 seconds beginning at one minute, each time.
呼吸疾病患者的自主呼吸频率（f）可以被认为是呼吸力学的指标。通过目视观察进行计数

f

是监控此功能的主要方式。应在可比条件下计算呼吸次数，以便进行有意义的系列比较。应避免在进行外部作（例如沐浴、吸痰和翻身）时进行计数。如果在短暂停用机械呼吸机期间测量到自发

f

性呼吸，则间隔应相同，例如，每次从 1 分钟开始 30 秒。

Several methods are available for continuous mechanical monitoring of spontaneous f . These include chest impedance, utilizing two electrocardiogram leads on the chest wall; and inductance, using insulated wire coils imbedded in a mesh vest. Electromyograms and magnetometers have been tried as continuous respiratory rate monitors, but they are not accurate enough in the critically ill patient for routine use. Three techniques sometimes used to detect airflow are insertion of a thermistor or thermodilution catheter in a nasal cannula, expiratory

{CO}_{2}

monitoring through such a cannula, and the use of a microphone placed over the trachea.
有几种方法可用于自发 f 的连续机械监测。这些包括胸阻抗，在胸壁上使用两条心电图导联;和电感，使用嵌入网状背心中的绝缘线圈。肌电图和磁力计已尝试用作连续呼吸频率监测器，但它们在危重患者中的常规使用不够准确。有时用于检测气流的三种技术是将热敏电阻或热稀释导管插入鼻插管，通过这种插管监测

{CO}_{2}

呼气，以及使用放置在气管上的麦克风。

Lung Volumes 肺容量

The lung volumes useful in management of the patient on a ventilator include expired tidal volume (VT), vital capacity (VC), and functional residual capacity (FRC). Although some ventilators
对使用呼吸机的患者进行管理有用的肺容量包括呼气量（VT）、肺活量（VC）和功能残活量（FRC）。虽然一些呼吸机
have built-in devices giving a breath-by-breath Vt readout, these must be checked for accuracy and often are only rough approximations. For VT and VC, the time-honored Wright Respirometer, a mechanical, spinning-vane spirometer, is still the most dependable, accurate, and durable device for routine use. Hand-held electronic spirometers may also be used, although their accuracy should be checked against a known volume, and they easily damaged by rough use or improper cleaning. water-seal or rolling-seal spirometer may leaning. A standard VT and VC, but bulk and more cor may be used for measuring less suitable for routine man complicated operation make these graphs that have becom management. Lightweight pneumotacho-graphuous VT measurements by integrating inspiratory or expiratory flow: These devices also register

f

and combine it with VT to compute Ve.
具有内置设备，可提供逐次呼吸的 Vt 读数，必须检查这些设备的准确性，并且通常只是粗略的近似值。对于 VT 和 VC，历史悠久的 Wright 呼吸计是一种机械旋片肺活量计，仍然是日常使用中最可靠、最准确和最耐用的设备。也可以使用手持式电子肺活量计，但应根据已知体积检查其准确性，并且它们很容易因粗暴使用或清洁不当而损坏。水封或滚动密封肺活量计可能倾斜。标准的 VT 和 VC，但体积和更多的 cor 可用于测量，不太适合常规的人工复杂作，使这些图表成为管理。通过整合吸气或呼气流量进行轻型肺气流-图形 VT 测量：这些设备还记录

f

并将其与 VT 相结合以计算 Ve。

Measurements of expired Vt during mechanical ventilation must take into consideration the expansion volume of the ventilator tubing. As a rule of thumb, in standard disposable circuits this volume is approximately

3 ml / cm H_{2} O

of static airway pressure. In patients with ARDS and other conditions producing marked lung stiffness, this compression volume can be considerable. Direct measurement rather than calculated estimation of this volume is necessary for research applications but not for day-to-day clinical management so long as the same technique is used each time Vt is measured.
机械通气期间呼出的 Vt 测量必须考虑呼吸机管的膨胀容积。根据经验，在标准一次性回路中，该体积大约

3 ml / cm H_{2} O

为静态气道压力。对于患有 ARDS 和其他产生明显肺僵硬的疾病的患者，这个按压量可能相当大。对于研究应用来说，直接测量而不是计算估计这个体积是必要的，但对于日常临床管理来说不是，只要每次测量 Vt 时都使用相同的技术。

Because ARDS is characterized by a reduction in FRC, and because positive end-expiratory pressure (PEEP) therapy is geared physiologically to increase FRC in order to improve arterial oxygenation, direct measurement of FRC during the course and therapy of these disorders would be a valuable monitoring tool. Unfortunately, although several devices and protocols have been published for measuring FRC in ventilated patients, none of these is simple enough for routine use. Only an indirect assessment of FRC through the chest roentgenogram is presently available outside the specialized research setting.
由于 ARDS 的特征是 FRC 降低，并且因为呼气末正压（PEEP）治疗在生理上旨在增加 FRC 以改善动脉氧合，因此在这些疾病的病程和治疗期间直接测量 FRC 将是一种有价值的监测工具。不幸的是，尽管已经发布了几种用于测量通气患者 FRC 的设备和协议，但这些都不够简单，无法常规使用。目前，在专业研究环境之外，只能通过胸部 X 线片对 FRC 进行间接评估。
Auto-PEEP. During mechanical ventilation, particularly with the assisted mechanical ventilation (AMV) or controlled mechanical ventilation (CMV) modes, patients with airflow obstruction may fail to complete exhalation before the next ventilator breath begins. When this happens, progressive air trapping results, raising FRC and causing inadvertent “auto-PEEP.” This auto-PEEP effect can seriously reduce cardiac filling pressures, alter vascular pressure readings, and cause cardiovascular compromise. Auto-PEEP can be measured by stopping expiratory airflow at end-expiration just prior to the next breath and allowing the pressure inside the airways and in the ventilator tubing to equilibrate; auto-PEEP is read directly from the ventilator’s pressure manometer. Several currently manufactured ICU ventilators incorporate mechanisms for the semiautomated measurement of auto-PEEP.
自动 PEEP。在机械通气期间，特别是使用辅助机械通气（AMV）或受控机械通气（CMV）模式时，气流阻塞患者可能无法在下一次呼吸机呼吸开始前完成呼气。发生这种情况时，会导致渐进性空气滞留，提高 FRC 并导致无意的“自动 PEEP”。这种自体 PEEP 效应会严重降低心脏充盈压，改变血管压读数，并导致心血管损害。可以通过在下一次呼吸前在呼气末停止呼气气流，并让气道内和呼吸机管内的压力达到平衡来测量 Auto-PEEP;自动 PEEP 直接从呼吸机的压力计中读取。目前制造的几种 ICU 呼吸机集成了自体 PEEP 的半自动测量机制。

Measures io reduce or eliminate auto-PEEP do so by increasing expiratory time and include the following:
减少或消除自体 PEEP 的措施通过增加呼气时间来实现，包括以下内容：

Correcting respiratory alkalosis by reducing $f$ and/or VT. 2. Increasing inspiratory flow rate (which will increase peak inspiratory pressure as a reflection of resistance to flow in large airways, but will not increase the risk of barotrauma).
通过减少 $f$ 和/或 VT 来纠正呼吸性碱中毒。2. 增加吸气流速（这将增加吸气峰值压力，反映出大气道中对流动的阻力，但不会增加气压伤的风险）。
Replacing the standard high-compressible-volume disposable ventilator circuit with a nondisposable, low-compressible-volume circuit (which will decrease the total volume the ventilator must deliver with each breath, shortening the time required to deliver it) it).
用非一次性、低可压缩体积的回路（这将减少呼吸机每次呼吸必须输送的总体积，缩短输送所需的时间）取代标准的高可压缩体积一次性呼吸机回路）。

Patients who are making some spontaneous breathing effort (with either AMV or IMV) in the presence of auto-PEEP must overcome the latter to initiate each breath, thus increasing breathing work. For example, if a patient has

12 cm H_{2} O

of auto-PEEP because of incomplete lung emptying prior to the delivery of the next breath, and if it takes

- 3 cm H_{2} O

to trigger that next breath, then the patient must perform sufficient ventilatory muscle work to generate

12 + 3 = 15 cm H_{2} O

every time a breath is taken. Adding dialed-in PEEP (external PEEP) to a level near that of the patient’s own auto-PEEP may reduce this added work of breathing and relieve patient distress. However, this should not be done if it results in an increase in the total PEEP measured using the auto-PEEP maneuver.
在存在自体 PEEP 的情况下进行一些自主呼吸努力（使用 AMV 或 IMV）的患者必须克服后者才能开始每次呼吸，从而增加呼吸功。例如，如果患者由于在下一次呼吸前肺排空不完全而患有

12 cm H_{2} O

自体 PEEP，并且需要

- 3 cm H_{2} O

触发下一次呼吸，那么患者必须进行足够的通气肌肉工作，以便在每次呼吸时产生

12 + 3 = 15 cm H_{2} O

。将拨入式 PEEP（外部 PEEP）添加到接近患者自身自身自动 PEEP 的水平可能会减少这种增加的呼吸工作并缓解患者的痛苦。但是，如果它导致使用自动 PEEP 作测量的总 PEEP 增加，则不应这样做。

Respiratory System Compliance
呼吸系统顺应性

Definition. Compliance measures the change in pressure

(Δ P)

required to produce a certain volume

(Δ V)

; thus, compliance

=

Δ V / Δ P

. Respiratory system compliance (CRS) is the pressure required to inflate the lungs and move the chest wall with a given volume of gas. Its two components, lung compliance and chest wall compliance, are altered by many disease processes but are difficult to measure separately, especially in sick, mechanically ventilated patients. For this reason, approximations of Crs under dynamic and static conditions are used.
定义。柔度测量产生一定体积

(Δ V)

所需的压力

(Δ P)

变化;因此，合规性

=

Δ V / Δ P

.呼吸系统顺应性（CRS）是用给定体积的气体给肺部充气和移动胸壁所需的压力。它的两个组成部分，肺顺应性和胸壁顺应性，会因许多疾病过程而改变，但很难单独测量，尤其是在生病的机械通气患者中。因此，使用动态和静态条件下 Crs 的近似值。

Dynamic Compliance. Dynamic respiratory system compliance (CDYN) is a measure of the maximum airway pressure (PMAX) required to deliver a given VT to a ventilated patient, minus the amount of PEEP also used to expand the lungs. Thus, CDYN = Vt/(Pmax - PEEP). As dynamic measurements, CDYN and Pmax reflect the resistance to gas flow in the airways and ventilator tubing as well as the compliance characteristics of the lungs and chest wall. Peak airway pressure will rise and CDYN will fall in the presence of bronchospasm, airway secretions, a small endotracheal tube, an agitated patient, or any combination of these.
动态合规性。动态呼吸系统顺应性（CDYN）是衡量向通气患者输送给定 VT 所需的最大气道压力（PMAX）的指标，减去也用于扩张肺部的 PEEP 量。因此，CDYN = Vt/（Pmax - PEEP）。作为动态测量，CDYN 和 Pmax 反映了气道和呼吸机管道中气流的阻力以及肺和胸壁的顺应性特性。在支气管痉挛、气道分泌物、小气管插管、激越的患者或这些的任意组合存在的情况下，气道峰值压力会升高，CDYN 会下降。

Static Compliance. Static respiratory system compliance (Cstat) is a measure of the airway pressure (PSTAT) required to hold the lungs and chest wall at end-inspiration after a VT has been delivered and gas flow is not present. The amount of PEEP being used should be subtracted; thus, Cstat

= Vt / (

Pstat - PEEP

)

. A normal value is 60 to

90 ml / cm H_{2} O

. As static measurements, Cstat and Pstat reflect only the compliance of the lungs and chest wall and are not affected by resistance to gas flow. Static airway pressure will rise, and Cstat will fall, in the presence of lung stiffness, which is most pronounced in ARDS, and also with abnaliti, of the is pronoun abnormalities of the chest wall, such as obesity, vigorous respiratory muscle contraction, and casts and bandages that limit movement. Tension pneumothorax and large pleural effusions also make Cstat fall.
静态合规性。静态呼吸系统顺应性（Cstat）是衡量 VT 输送且不存在气流后，在吸气末保持肺和胸壁所需的气道压力（PSTAT）的量度。应减去正在使用的 PEEP 量;因此，Cstat

= Vt / (

Pstat - PEEP

)

.正常值为 60 到

90 ml / cm H_{2} O

。作为静态测量，Cstat 和 Pstat 仅反映肺和胸壁的顺应性，不受气流阻力的影响。在肺僵硬的情况下，静态气道压力会上升，Cstat 会下降，这在 ARDS 中最为明显，并且在 abnaliti 中也是如此，胸壁的代词异常，例如肥胖、剧烈的呼吸肌收缩，以及限制运动的石膏和绷带。张力性气胸和大量胸腔积液也使 Cstat 下降。

Serial Compliance Measurements. Although single determinations of Cdyn and Cstat provide some information, serial measurements are more helpful. Abrupt increases in Cdyn but not Cstat may provide important clues as to the presence of airflow obstruction; on the other hand, decreases in Cstat but not Cdyn may reflect increased lung stiffness as found in pulmonary edema. Multiple-breath volume-pressure curves may also be generated at the bedside using serial measurements of dynamic airway pressure (Pdyn) and Pstat at different Vts. Plotting Vts against Pdyns produces a dynamic compliance curve; plotting Vts against Pstats produces a static compliance curve. In the presence of increased airways resistance, the dynamic curve is shifted to the right and flattened, indicating a much higher PMAX with increasing VT, but the static curve is unchanged. The static wave is shifted to the right when preumotherax static wave is shifted to the right
串行一致性测量。尽管 Cdyn 和 Cstat 的单次测定提供了一些信息，但连续测量更有帮助。Cdyn 突然升高而 Cstat 未升高可能为存在气流阻塞提供重要线索;另一方面，Cstat 降低而不是 Cdyn 降低可能反映了肺水肿中发现的肺硬度增加。也可以在床旁使用不同 Vts 的动态气道压力（Pdyn）和 Pstat 的连续测量来生成多次呼吸量-压力曲线。绘制 Vts 与 Pdyns 的关系图可产生动态顺应性曲线;绘制 Vts 与 Pstats 的关系会产生一条静态柔度曲线。在气道阻力增加的情况下，动态曲线向右移动并变平，表明 PMAX 随着 VT 的增加而高得多，但静态曲线保持不变。当 preumotherax 静波向右移动时，静波向右移动

Flow Rates 流速

Measurements of expiratory volume in the first second of a forced vital capacity maneuver (

{FEV}_{1}

) are possible in intubated patients but are rarely made. Spontaneously breathing, nonintubated patients with severe airflow obstruction, such as individuals with status asthmaticus, may be able to perform this maneuver, and serial

{FEV}_{1}

determinations are sometimes used in following these patients acutely. More commonly employed in this setting is the measurement of peak flow, which is often better tolerated and can be done with convenient portable devices such as the MiniWright Peak Flow Meter.
在气管插管患者中，可以在用力肺活量作（

{FEV}_{1}

）的第一秒测量呼气容积，但很少进行。有严重气流阻塞的自主呼吸、非插管患者（例如哮喘持续状态患者）可能能够进行该作，有时在急性随访这些患者时采用连续

{FEV}_{1}

测定法。在这种情况下，更常用的是峰值流量的测量，这通常耐受性更好，并且可以使用方便的便携式设备（如 MiniWright 峰值流量计）来完成。

Respiratory Muscle Function
呼吸肌功能

Although diaphragmatic and intercostal electromyography are used in research, clinical respiratory muscle function is usually assessed by bedside observation and measurement of maximum
虽然在研究中使用了膈肌和肋间肌电图，但临床呼吸肌功能通常通过床旁观察和测量最大值来评估
inspiratory force (MIF), as discussed in Chapter 6. Discoordination of chest and abdominal muscles during spontaneous breathing or patient-initiated breathing during mechanical ventilation produces a pattern similar to that seen with bilateral diaphragmatic paralysis, as described in Chapter 5. This finding is predictive of risk for acute ventilatory failure and of difficulty in weaning from the ventilator.
吸气力（MIF），如第 6 章所述。自主呼吸或机械通气期间患者发起呼吸期间胸部和腹部肌肉不协调会产生类似于双侧膈肌麻痹的模式，如第 5 章所述。这一发现可预测急性通气衰竭的风险和脱离呼吸机的困难。

MONITORING GAS EXCHANGE 监测气体交换

Oxygenation of the Arterial Blood
动脉血氧合

General Considerations. The maintenance of adequate arterial oxygenation, as reflected in the arterial oxygen tension

({PaO}_{2})

, is one of the fundamental goals of respiratory intensive care. Arterial oxygenation can be monitored either intermittently or continuously, and several different techniques are available.
一般注意事项。维持足够的动脉氧合，如动脉氧分压

({PaO}_{2})

所反映的那样，是呼吸重症监护的基本目标之一。动脉氧合可以间歇性或连续性监测，并且有几种不同的技术可供选择。

Inspired Oxygen Fraction. Measurement or approximation of the

{PaO}_{2}

is most useful when compared with the concurrent fraction of inspired

O_{2} ({FIO}_{2})

. Some ventilators have built-in sensors to measure

{FIO}_{2}

, although the accuracy of these devices varies and must be checked against a more reliable

O_{2}

analyzer. Various analyzers are available; some have rapid response time, although this is not necessary for routine clinical measurement. The introduction of mass spectrometry into some intensive care units has made rapid, continuous, accurate

{FIO}_{2}

monitoring possible in routine patient care, although the overall need for this outside the research setting remains to be seen.
吸入氧分数。与 inspired

O_{2} ({FIO}_{2})

的并发分数相比，的

{PaO}_{2}

测量或近似值最有用。一些呼吸机有内置传感器进行测量

{FIO}_{2}

，尽管这些设备的准确性各不相同，必须与更可靠的

O_{2}

分析仪进行检查。提供各种分析仪;有些具有快速响应时间，尽管这对于常规临床测量不是必需的。在一些重症监护病房中引入质谱技术后，在常规患者护理中实现了快速、连续、准确的

{FIO}_{2}

监测，尽管在研究环境之外对质谱的总体需求仍有待观察。

Arterial Oxygen Tension. The

{PaO}_{2}

may be measured in a 2- to

3 - ml

sample obtained from either percutaneous arterial puncture or indwelling arterial catheter. Repeated percutaneous sticks, if done with skill using a small-bore (25-gauge) needle, are safe even when repeated dozens of times over the course of a week. Their disadvantages are inconvenience, the risk of bleeding if the site is not held under pressure or if the patient is anticoagulated, and the pain they cause. Arterial catheters are convenient once in place and allow rapid, reliable arterial access for multiple specimens. They carry a higher risk for complications such as ischemia and embolization than do percutaneous sticks, however, and may be overused. Arterial lines are necessary when hemodynamic instability demands continuous arterial pressure monitoring, and are justified when multiple blood samples must be obtained in critically ill patients, for example, during PEEP trials. Although indwelling continuous arterial blood gas samplers with either fine catheters or
动脉血氧分压。

{PaO}_{2}

可以在从经皮动脉穿刺或留置动脉导管获得的 2 对

3 - ml

样本中测量。如果使用小口径（25 号）针头熟练地完成重复经皮支扎，即使在一周内重复数十次也是安全的。它们的缺点是不便、如果该部位没有承受压力或患者接受抗凝治疗，则有出血的风险，以及它们引起的疼痛。动脉导管一旦就位就位就方便，即可快速、可靠地为多个样本提供动脉通路。然而，与经皮栓塞相比，它们发生缺血和栓塞等并发症的风险更高，并且可能被过度使用。当血流动力学不稳定需要持续监测动脉压时，动脉导管是必要的，当危重患者必须获得多个血样时，例如在 PEEP 试验期间，动脉导管是合理的。虽然留置连续动脉血气采样器带有细导管或
intra-arterial electrodes are available, they are not yet sufficiently accurate or reliable for routine use.
动脉内电极可用，但它们对于常规使用还不够准确或可靠。

Capillary and Venous Oxygen Tension. Systemic capillary or arterialized peripheral venous blood can be used in certain settings to reflect arterial pH and carbon dioxide tension

({PCO}_{2})

. However, the oxygen tension

({PO}_{2})

of these sources is lower than that of arterial blood, especially if local blood flow is impaired. These measurements do not have a significant role in the management of adult patients in the ICU.
毛细血管和静脉氧分压。在某些情况下，可以使用全身毛细血管或动脉化外周静脉血来反映动脉 pH 值和二氧化碳分压

({PCO}_{2})

。然而，这些来源的氧分压低于动脉血的氧分压

({PO}_{2})

，尤其是在局部血流受损的情况下。这些测量在 ICU 成年患者的管理中没有重要作用。

Transcutaneous Oxygen Tensions. Transcutaneous

{PO}_{2} ({PtcO}_{2})

monitors accurately reflect

{PaO}_{2}

in neonates and small children, but not in adults because of their thicker dermis; they also are inaccurate in the presence of varying peripheral perfusion. Thus,

{PtcO}_{2}

, monitoring is not acceptable as a sole index of oxyge in adult patients whose condition is unstable.
经皮氧分压。经皮监护仪

{PO}_{2} ({PtcO}_{2})

在新生儿和幼儿中准确反映，但在成人中则不能准确反映

{PaO}_{2}

，因为他们的真皮较厚;在存在不同外周灌注的情况下，它们也不准确。因此，

{PtcO}_{2}

监测作为病情不稳定的成年患者的 oxyge 的唯一指标是不可接受的。

Pulse Oximetry. The availability of accurate, reliable pulse oximeters has made continuous monitoring of arterial

O_{2}

saturation

({SaO}_{2})

practical in several clinical settings. These devices are important in the evaluation of sleep disorders, in regulating lowflow

O_{2}

therapy in some patients with severe chronic obstructive pulmonary disease (COPD), and in clinical exercise testing. They may also be helpful in the continuous assessment of patients whose

{PaO}_{2}

values are below about 65 mmHg . Above this

{PaO}_{2}

, because of the flat shape of the

O_{2}

-hemoglobin dissociation curve, the pulse oximeter is less useful as a monitoring tool. Its accuracy is about

\pm 3

per cent, and hemoglobin is effectively completely saturated at

{PaO}_{2}

values in excess of about 80 mmHg , so that its value in continuous monitoring is mainly in the detection of falls in

{PaO}_{2}

below this level. The pulse oximeter cannot distinguish between

{PaO}_{2}

values of 100 and 300 mmHg . It may also be inaccurate in the presence of high serum bilirubin concentrations, green dye (used in some determinations of cardiac output by indicator dilution), and poor ear perfusion.
脉搏血氧测定法。准确、可靠的脉搏血氧仪的可用性使得在多种临床环境中

({SaO}_{2})

持续监测动脉

O_{2}

血氧饱和度变得实用。这些设备在评估睡眠障碍、调节一些严重慢性阻塞性肺疾病（COPD）患者的低流量

O_{2}

治疗以及临床运动测试中非常重要。它们还可能有助于对

{PaO}_{2}

值低于约 65 mmHg 的患者进行持续评估。在此

{PaO}_{2}

之上，由于

O_{2}

- 血红蛋白解离曲线的平坦形状，脉搏血氧仪作为监测工具的用处较小。它的准确性约为

\pm 3

%，血红蛋白在

{PaO}_{2}

超过 80 mmHg 的值时实际上完全饱和，因此它在连续监测中的价值主要在于检测

{PaO}_{2}

低于该水平的跌落。脉搏血氧仪无法区分 100 和 300 mmHg

{PaO}_{2}

的值。在血清胆红素浓度高、绿色染料（用于通过指示剂稀释测定心输出量的某些指标）和耳灌注不良的情况下，也可能不准确。

Alveolar-Arterial Oxygen Differences. The adequacy of oxygen transfer from alveolus to arterial blood can be assessed precisely are known. Alveolar

{PO}_{2}

and the alveolar air can be estimated using the measured

{FiO}_{2}

and equation (see Chapter 2) and from this an alveolar-arterial

O_{2}

difference or gradient

[P (A - a) O_{2}]

can be calculated.
肺泡-动脉氧差异。可以精确评估氧气从肺泡转移到动脉血的充分性是已知的。肺泡

{PO}_{2}

和肺泡空气可以使用测量

{FiO}_{2}

方程（见第 2 章）进行估计，由此

[P (A - a) O_{2}]

可以计算出肺泡-动脉差异

O_{2}

或梯度。

A rough approximation of the

P (A - a) O_{2}

can be derived from the ratio of

{PaO}_{2}

{FIO}_{2}

(

P / F

ratio). This easy calculation allows comparison of serial

{PO}_{2}

determinations even when

{FIO}_{2}

varies, and is acceptably accurate over the range of

{FIO}_{2}

of 0.40 to 0.70 . Thus, if a patient has a

{PaO}_{2}

of 80 mmHg on an

{FIO}_{2}

of 0.40 , the P/F ratio is 200 , which would be the same if this patient had a
可以从

{PaO}_{2}

的

{FIO}_{2}

比率（

P / F

ratio）中得出 the

P (A - a) O_{2}

的粗略近似值。这种简单的计算允许在变化时

{FIO}_{2}

对序列

{PO}_{2}

测定进行比较，并且在 0.40 至 0.70 的范围内

{FIO}_{2}

是可接受的准确度。因此，如果患者的 P/F 为 80 mmHg，

{FIO}_{2}

而 P/F 比为 200，如果该患者的 P

{PaO}_{2}

/F 为

{PaO}_{2}

of 120 mmHg on an

{FIO}_{2}

of 0.60 . A worsening of arterial blood oxygenation may be detected using P/F ratios even when

{FIO}_{2}

has been changed since the previous specimen was obtained.

{PaO}_{2}

120 mmHg 在

{FIO}_{2}

0.60 .使用 P/F 比值可以检测到动脉血氧合恶化，即使自获得先前标本以来

{FIO}_{2}

已经改变。

Alveolar Ventilation 肺泡通气

General Considerations. As discussed in Chapter 2, the body normally maintains an alveolar and arterial

{PCO}_{2}

of approximately 40 mmHg by adjusting alveolar ventilation (VA) to meet its

{CO}_{2}

production

({VCO}_{2})

. This process is symbolized in the alveolar ventilation equation:

{PACO}_{2} = {PaCO}_{2} = {VCO}_{2} / VA

. Assuming a near-constant

{VCO}_{2}

, the

{PaCO}_{2}

is an accurate reflection of VA , and hyperventilation and hypoventilation are defined by this measurement.
一般注意事项。如第 2 章所述，身体通常通过调整肺泡通气（VA）来维持约 40 mmHg 的肺泡和动脉

{PCO}_{2}

以满足其

{CO}_{2}

产生

({VCO}_{2})

。这个过程在肺泡通气方程中表示：

{PACO}_{2} = {PaCO}_{2} = {VCO}_{2} / VA

。假设几乎恒定

{VCO}_{2}

，则

{PaCO}_{2}

准确反映了 VA ，并且过度换气和通气不足由此测量定义。

Arterial Carbon Dioxide Tension. Monitoring

{PaCO}_{2}

is subject to the same constraints as with

{PaO}_{2}

: An arterial sample is required, and with present technology this means intermittent rather than continuous assessment.
动脉二氧化碳分压。监测

{PaCO}_{2}

受到与以下

{PaO}_{2}

相同的限制：需要动脉样本，而根据目前的技术，这意味着间歇性评估而不是连续评估。

Transcutaneous Carbon Dioxide Tension. Transcutaneous

{PCO}_{2}

({PtcCO}_{2})

, although slightly higher than

{PaCO}_{2}

, is a reflection of the latter in hemodynamically stable patients. Although subject to limitations similar to those for

{PtcO}_{2}

, the cutaneous monitoring of

{PCO}_{2}

may become more useful in detecting acute changes and trends in VA while allowing fewer arterial blood specimens to be drawn. At present, however, the

{PtCO}_{2}

should be thought of as a supplement to, but not a replacement for, the

{PaCO}_{2}

.
经皮二氧化碳分压。经皮

{PCO}_{2}

({PtcCO}_{2})

，虽然略高于

{PaCO}_{2}

，但反映了后者在血流动力学稳定的患者中。尽管受到与类似的

{PtcO}_{2}

限制，但皮肤监测

{PCO}_{2}

可能在检测 VA 的急性变化和趋势方面变得更有用，同时允许抽取更少的动脉血标本。然而，目前应将 the

{PtCO}_{2}

视为

{PaCO}_{2}

的补充，而不是替代。

Expired Gas Tension. Measuring

{PCO}_{2}

in expired gas rather than in blood (capnography) currently is an adjunct to other monitoring techniques and in certain circumstances can replace repeated arterial sampling. In normal individuals, end-tidal expired

{PCO}_{2}

({PetCO}_{2})

is approximately the same as

{PaCO}_{2}

and

{PaCO}_{2}

. However, in patients with a large physiological dead space (VD), with extensive ventilation and perfusion (VA/Q) mismatching, or with prolonged expiration due to severe COPD or asthma,

{PETCO}_{2}

is not an accurate measure of VA. Because changes in either

{PaCO}_{2}

\dot{VA} / \dot{Q}

distribution can change

{PetCO}_{2}

, this measure can also be misleading if used to follow trends between arterial samplings. Thus, patients with severe respiratory insufficiency of any cause and patients whose condition is acutely unstable from either a cardiovascular or a respiratory standpoint are not candidates for continuous end-tidal

{CO}_{2}

monitoring as a primary surveillance technique.
过期气体张力。目前，用呼出的气体而不是血液（二氧化碳图）进行测量

{PCO}_{2}

是其他监测技术的辅助手段，在某些情况下可以替代重复的动脉采样。在正常个体中，呼气末过期

{PCO}_{2}

({PetCO}_{2})

与

{PaCO}_{2}

和

{PaCO}_{2}

大致相同。然而，对于生理死腔（VD）较大的患者，广泛通气和灌注（VA/Q）不匹配，或由于严重 COPD 或哮喘而延长呼气时间，

{PETCO}_{2}

并不是 VA 的准确衡量标准。因为 or

{PaCO}_{2}

\dot{VA} / \dot{Q}

分布的变化可能会发生变化

{PetCO}_{2}

，所以如果用于跟踪动脉采样之间的趋势，该指标也可能具有误导性。因此，任何原因导致的严重呼吸功能不全患者以及从心血管或呼吸角度来看病情急性不稳定的患者都不适合将持续呼气末

{CO}_{2}

监测作为主要监测技术。
Mixed expired

{CO}_{2}

tension (

{PeCO}_{2}

) is also a useful measurement in respiratory care. It reflects overall ventilatory efficiency in that the lower the

{PECO}_{2}

in relation to

{PaCO}_{2}

, the higher the patient’s
混合呼

{CO}_{2}

气张力（

{PeCO}_{2}

）也是呼吸护理中的一种有用测量方法。它反映了整体通气效率，因为相对于越低

{PECO}_{2}

{PaCO}_{2}

，患者的通气效率越高

Vd. The

{PECO}_{2}

in pooled expiratory gas samples is necessary for measuring

{VCO}_{2}

and the dead space to tidal volume ratio (VD/ VT ) in assessment for ventilator weaning.
Vd.

{PECO}_{2}

混合呼气样本对于测量

{VCO}_{2}

是必要的，死腔与潮气量比（VD/VT）在评估呼吸机脱机时是必要的。

pH 酸碱度

Arterial pH is an index of the body’s acid-base status as affected by respiratory and metabolic processes. The pH is necessary in judging whether abnormal

{PaCO}_{2}

values are acute or chronic and whether they threaten life, as described in Chapter 7. At present, arterial pH can be monitored only by repeated arterial blood gas sampling.
动脉 pH 值是人体受呼吸和代谢过程影响的酸碱状态的指标。如第 7 章所述，pH 值在判断异常

{PaCO}_{2}

值是急性还是慢性以及它们是否威胁生命时是必要的。目前，只能通过重复动脉血气采样来监测动脉 pH 值。

MONITORING OXYGEN TRANSPORT
监测氧气运输

General Considerations 一般注意事项

Systemic

O_{2}

transport, as discussed in Chapters 2 and 7, is equal to the product of the amount of

O_{2}

carried in arterial blood, the arterial

O_{2}

content

({CaO}_{2})

, and the total blood flow to the tissues, the cardiac (left ventricular) output (QT). Thus, systemic

O_{2}

transport

= {CaO}_{2} \times QT

.
如第 2 章和第 7 章所述，全身

O_{2}

转运等于动脉血中携带的

O_{2}

量、动脉

O_{2}

内容

({CaO}_{2})

物和流向组织的总血流量、心脏（左心室）输出量（QT）的乘积。因此，全身

O_{2}

运输

= {CaO}_{2} \times QT

Arterial Oxygen Content 动脉血氧含量

The

{CaO}_{2}

is equal to the hemoglobin concentration in grams per 100 ml of blood times the

O_{2}

carrying capacity of the hemoglobin (normally

1.34 ml O_{2} / gm

) times the

{SaO}_{2}

, plus the small amount of

O_{2}

normally dissolved in blood (

0.003 ml / 100 ml

) times the

{PaO}_{2}

. All these variables can be measured; the most important are the hemoglobin concentration and the

{SaO}_{2}

.
等于

{CaO}_{2}

每 100 毫升血液中的血红蛋白浓度（克）乘以血红蛋白（正常

1.34 ml O_{2} / gm

）

O_{2}

的承载能力乘以

{SaO}_{2}

，加上少量正常溶解在血液中的

O_{2}

血红蛋白（

0.003 ml / 100 ml

）乘以

{PaO}_{2}

。所有这些变量都可以测量;最重要的是血红蛋白浓度和

{SaO}_{2}

Cardiac Output 心输出量

Calculated Values. The

\dot{Q} T

is the product of heart rate (HR) and stroke volume (SV); it also may be calculated by dividing the systemic perfusion pressure [mean arterial pressure (MAP) minus right atrial pressure] by the systemic vascular resistance (SVR). Although HR is easily counted and SV can be measured by echocardiographic techniques, determinations of the latter variables are relatively crude so far. The SVR cannot be measured directly, although MAP and right atrial pressure can be, so other methods are used to measure

\dot{Q T}

.
计算值。它是

\dot{Q} T

心率（HR）和每搏输出量（SV）的乘积;它也可以通过将体循环灌注压 [平均动脉压（MAP）减去右心房压] 除以体循环血管阻力（SVR）来计算。尽管 HR 很容易计数并且 SV 可以通过超声心动图技术测量，但到目前为止，后一个变量的测定相对粗略。SVR 不能直接测量，尽管 MAP 和右心房压可以测量，因此使用其他方法进行测量

\dot{Q T}

。

Indicator Dilution. The most commonly used clinical method for measuring

{\dot{Q}}_{T}

is the indicator dilution technique. Although dyes may be used for this purpose, thermodilution is usually employed.
指示剂稀释。临床最常用的测量

{\dot{Q}}_{T}

方法是指示剂稀释技术。虽然染料可用于此目的，但通常采用热稀释法。

256 / MONITORING THE PATIENT
256 / 监测病人

Thermodilution requires a catheter with openings in the right atrium and in the pulmonary artery. A bolus of cold liquid is injected rapidly into the right atrium, causing its negative heat to be diluted by mixing with blood as it passes from the right atrium, through the right ventricle, and into the pulmonary artery. A thermistor senses the temperature of the blood passing the distal catheter opening, and with the aid of a computer, the area under the cooling curve caused by the injected bolus can be calculated and expressed as Qt in liters per second. Five per cent glucose in water, 10 ml at

0^{\circ} C

, is used for the cold injection in adult patients. Care is taken to inject the bolus at a constant, reproducible rate, and the average of three measurements is used as the QT.
热稀释法需要在右心房和肺动脉中开通导管。将一团冷液体迅速注入右心房，使其负热在从右心房通过右心室进入肺动脉时与血液混合而被稀释。热敏电阻感应通过远端导管开口的血液温度，在计算机的帮助下，可以计算出由注射的推注引起的冷却曲线下的面积，并以每秒升数表示为 Qt。5% 葡萄糖水溶液，10 ml at

0^{\circ} C

，用于成年患者的冷注射。注意以恒定、可重复的速率注射推注，并将三次测量的平均值用作 QT。

The thermodilution technique has several potential limitations, the most important of which is that it measures right ventricular output, which may differ from that of the left ventricle from beat to beat. Thermodilution also has several possible sources of error, on the part of the person performing the measurements and the instruments used. (The references listed at the end of this chapter provide further information.)
热稀释法有几个潜在的局限性，其中最重要的是它测量右心室输出量，这可能与左心室的心输出量不同。热稀释法也有几个可能的误差源，与执行测量的人员和使用的仪器有关。（本章末尾列出的参考资料提供了更多信息。

The Fick Method. The Fick equation holds that QT is equal to the body’s

O_{2}

consumption (

{VO}_{2}

) divided by the amount of

O_{2}

extracted by the peripheral tissues, which is the difference between the arterial and mixed venous

O_{2}

contents

[{CaO}_{2} - C \overset{―}{v} O_{2}

C (a - \overset{―}{v}) O_{2}]

. The

{CaO}_{2}

and

C \overset{―}{v} O_{2}

can be calculated from simultaneously obtained samples of arterial and mixed venous blood; a pulmonary artery catheter is required for the latter. The

{VO}_{2}

may be calculated from the differences between the inspired and expired fractions of

O_{2} ({FIO}_{2}, {FEO}_{2})

in a sampling of expired gas. However, gas samples are technically difficult to collect in mechanically ventilated patients, and the difference between

{FIO}_{2}

and

{FEO}_{2}

approaches the measurement error for most

O_{2}

analyzers when

V_{E}

exceeds

10 L / \min

, as it often does in patients. One way around these logistical difficulties is to assume that

{VO}_{2}

is constant and equal to the normal value of

250 ml / \min

. Unfortunately, however, these assumptions rarely apply to sick patients. Thus, although the Fick principle provides conceptual insights (as discussed later in this chapter), it is difficult to use in intensive care monitoring.
菲克方法。菲克方程认为 QT 等于身体

O_{2}

的消耗量（

{VO}_{2}

）除以外周组织提取的

O_{2}

量，即动脉内容物和混合静脉

O_{2}

内容

[{CaO}_{2} - C \overset{―}{v} O_{2}

物之间的差值或

C (a - \overset{―}{v}) O_{2}]

。和

{CaO}_{2}

C \overset{―}{v} O_{2}

可以从同时获得的动脉血和混合静脉血样本中计算;后者需要肺动脉导管。

{VO}_{2}

可以根据呼出气体采样

O_{2} ({FIO}_{2}, {FEO}_{2})

中的吸气馏分和呼出馏分之间的差异来计算。然而，在机械通气的患者中，气体样品在技术上很难收集，并且和之间的差异

{FIO}_{2}

接近大多数

O_{2}

分析仪的测量误差，就像

V_{E}

10 L / \min

在患者中经常出现

{FEO}_{2}

的那样。解决这些逻辑困难的一种方法是假设是

{VO}_{2}

常数并等于的正常值

250 ml / \min

。然而，不幸的是，这些假设很少适用于病人。因此，尽管 Fick 原则提供了概念性见解（如本章后面讨论），但它很难用于重症监护监测。

INVASIVE HEMODYNAMIC MONITORING TECHNIQUES
有创血流动力学监测技术

Arterial Catheters 动脉导管

As noted previously, the need for continuous pressure monitoring and for repeated sampling of arterial blood often mandates that indwelling arterial catheters be used in critically ill patients. The main complications of arterial catheters-thrombosis and infection-can be minimized if care is taken in insertion and
如前所述，需要持续监测压力和反复采集动脉血样本，这通常要求危重患者使用留置动脉导管。动脉导管的主要并发症 - 血栓形成和感染 - 如果小心插入并且
maintenance and if the catheter is removed promptly when no longer essential.
维护和当导管不再必要时立即拔除。

Central Venous Catheters 中心静脉导管

Passage of a catheter into the right atrium via the superior or inferior vena cava permits measurement of right ventricular enddiastolic pressure (preload) and hence systemic return to the heart. However, in acute respiratory failure of any etiology, or in the presence of intrinsic cardiac disease, right atrial pressure cannot be assumed to reflect left atrial end-diastolic pressure, that is, leftsided filling pressure and left-ventricular preload. Elevated left atrial pressure can coexist with normal or even low right atrial pressures and vice versa because of differences in the compliance characteristic of the two ventricles. In addition, vena caval or right atrial blood cannot be used to represent mixed venous blood; the latter must be sampled from the pulmonary artery to avoid the from inadequate mixing. Thus, central venous catheters provide adequate pressure monitoring or blood sampling for critically ill patients, and their use has diminished significantly.
导管通过上腔静脉或下腔静脉进入右心房，可以测量右心室舒张末期压力（前负荷），从而测量全身回流到心脏。然而，在任何病因的急性呼吸衰竭或存在内源性心脏病的情况下，不能假设右心房压反映了左心房舒张末期压力，即左心房充盈压和左心室前负荷。升高的左心房压可以与正常甚至低的右心房压共存，反之亦然，因为两个心室的顺应性特征不同。此外，腔静脉或右心房血不能用于表示混合静脉血;后者必须从肺动脉中取样，以避免混合不充分。因此，中心静脉导管为危重患者提供了足够的压力监测或血液采样，并且其使用已显着减少。

Balloon-Tipped Pulmonary Artery (Swan-Ganz) Catheters
球囊尖端肺动脉（Swan-Ganz）导管

General Considerations. Although direct measurement of left atrial pressures would permit monitoring of left ventricular preload, this is not done because of the difficulty and danger of the direct leftsided approach. However, if a catheter with an inflated balloon just proximal. to the distal tip is carried by the flow of blood into a branch of a pulmonary artery as far as it will go until it “wedges” there, so that the branch is momentarily occluded and blood flow in it and its downstream pulmonary vein ceases, then the pressure sensed by the catheter tip will be that transmitted back through the pulmonary veins from the left atrium. In other words, during peripheral pulmonary artery occlusion, the pulmonary artery wedge pressure (Ppaw) reflects left atrial pressure, which is the same as left ventricular pressure at end-diastole, when the mitral valve is open. Left-sided filling pressures can thus be monitored by a series of brief pulmonary artery occlusions, achieving access to left ventricular preload measurements without actually entering the left side of the heart.
一般注意事项。尽管直接测量左心房压力可以监测左心室前负荷，但由于直接测量左侧方法的困难和危险，因此没有这样做。但是，如果带有充气球囊的导管就在近端。到远端尖端被血液流入肺动脉的一个分支，直到它“楔入”那里，这样分支暂时被阻塞，其中的血流及其下游肺静脉停止，然后导管尖端感应到的压力将从左心房通过肺静脉传回。换句话说，在外周肺动脉闭塞期间，肺动脉楔压（Ppaw）反映了左心房压力，这与二尖瓣打开时舒张末期的左心室压力相同。因此，可以通过一系列短暂的肺动脉闭塞来监测左侧充盈压，无需实际进入心脏左侧即可获得左心室前负荷测量。

In addition to supplying information about Ppaw, the pulmonary artery catheter also can be used to determine pressures in the central veins, the right atrium and ventricle, and the pulmonary artery as it is being inserted. When the balloon is deflated and flow is present through the pulmonary artery, samples of mixed venous blood may be obtained through the tip. A hole at the right atrial level provides a site for the cold injection used for the thermodilution measurement of

\dot{Q}

T. Pulmonary artery catheters are also
除了提供有关 Ppaw 的信息外，肺动脉导管还可用于确定插入时中央静脉、右心房和心室以及肺动脉的压力。当球囊放气并且血流流经肺动脉时，可以通过尖端获得混合静脉血样本。右心房水平的孔为冷注射提供了用于 T 热

\dot{Q}

稀释度测量的部位。肺动脉导管也是
available with additional ports for assessing right ventricular function, and with fiberoptic bundles for continuous monitoring of mixed venous oxygen saturation.
提供用于评估右心室功能的附加端口，以及用于连续监测混合静脉血氧饱和度的光纤束。

Indications. The major indications for passage of a pulmonary artery catheter are:
迹象。肺动脉导管通过的主要适应症是：

To guide fluid management in critically ill patients, especially those with shock, ARDS, severe cardiac disease, and acute renal failure.
指导危重患者的液体管理，尤其是休克、ARDS、严重心脏病和急性肾功能衰竭患者。
To optimize $O_{2}$ transport and prevent cardiovascular compromise in PEEP therapy (especially important when levels above 10 to $15 cm H_{2} O$ are used).
在 PEEP 治疗中优化 $O_{2}$ 运输并防止心血管损害（当使用高于 10 的 $15 cm H_{2} O$ 水平时尤其重要）。
To separate cor pulmonale from left ventricular failure when this cannot be done with certainty using conventional clinical signs. 4. To assess the response to $O_{2}$ therapy and exercise in patients with severe pulmonary hypertension.
当使用常规临床体征无法确定时，将肺心病与左心室衰竭分开。4. 评估严重肺动脉高压患者对 $O_{2}$ 治疗和运动的反应。
To determine a patient’s ability to withstand pulmonary resection when other evaluation gives inconclusive results.
确定患者在其他评估得出不确定结果时耐受肺切除术的能力。

Insertion. Pulmonary artery catheters can be inserted through the internal jugular, subclavian, antecubital, and femoral approaches. Internal jugular and subclavian approaches offer large vessels, ease in maintaining sterility of the skin site, and a short path. The internal jugular route is less likely to cause pneumothorax; the subclavian approach has the advantage of stability in avoiding inadvertent catheter movement loft by mproach subclavian approaches offer the easiest route because of their unidirectional bend, whereas the femoral route can be more difficult, especially if the right ventricle is enlarged. Catheter placement is easy in the femoral vein; this location also can be useful in patients with low QT, although it is the hardest site to keep clean. The antecubital fossa gives easy access but usually requires a cutdown and thus damages the vein. It is often more difficult to thread the catheter from this insertion site, and arm movement can change the position of the catheter tip.
插入。肺动脉导管可通过颈内、锁骨下、肘前和股骨入路插入。颈内静脉和锁骨下入路提供大血管，易于保持皮肤部位的无菌性，路径短。颈内静脉途径不太可能引起气胸;锁骨下入路具有稳定性的优势，可以避免意外的导管移动 MProach 锁骨下入路提供了最简单的途径，因为它们是单向弯曲的，而股骨途径可能更困难，尤其是在右心室扩大的情况下。在股静脉中放置导管很容易;这个位置对低 QT 患者也很有用，尽管它是最难保持清洁的部位。肘前窝很容易进入，但通常需要切开，从而损害静脉。从该插入部位穿入导管通常更困难，手臂运动会改变导管尖端的位置。

Figure 16-1 shows how a catheter is passed into the pulmonary artery and illustrates the characteristic pressure tracings obtained at each site. The catheter is inserted through the skin and advanced until its tip enters the thorax, as indicated by the appearance of pressure swings with respiration. The balloon is then filled with air to the volume prescribed by the manufacturer. The catheter is advanced via the superior or inferior vena cava into and through the righ the tricuspid valve, and into the right atrium (Fig. 16-1A), past the right ventricle. Arrival in the ventricle is signaled by an increase in the systolic and pulse pressures on the tracing, with the normal 20 to 35 mmHg over zero (Fig. 16-1B). The catheter is advanced further, through the pulmonic valve and into the pulmonary artery, at which point the diastolic component of the pressure tracing rises as compared with that of the right ventricle (normal

= 20 / 5 mmHg

,
图 16-1 显示了导管如何进入肺动脉，并说明了在每个部位获得的特征性压力描记。导管穿过皮肤插入并推进，直到其尖端进入胸部，如呼吸时压力波动的出现所示。然后将气球充满空气，使其达到制造商规定的体积。导管通过上腔静脉或下腔静脉进入并通过右三尖瓣，然后进入右心房（图 16-1A），经过右心室。通过示踪上收缩压和脉压的增加来表示到达心室，正常的 20 至 35 mmHg 超过零（图 16-1B）。导管进一步推进，通过肺动脉瓣进入肺动脉，此时压力示踪的舒张期分量与右心室的舒张分量相比升高（正常

= 20 / 5 mmHg

，

MONITORING THE PATIENT 监测患者

Figure 16-1. Insertion of a balloon flotation catheter into the pulmonary artery, with accompanying pressure tracings at each step.

A

, Right atrium.

B

, Right ventricle.

C

, Pulmonary artery.

D

, Pulmonary artery “wedge” position.
图 16-1.将球囊漂浮导管插入肺动脉，并在每一步进行压力追踪。

A

右心房。

B

右心室。

C

肺动脉。

D

、肺动脉“楔形”位置。
mean 15 mmHg ) (Fig. 16-1C). Finally, the catheter is passed further into the pulmonary artery until its tip, surrounded by the balloon, impacts a smaller branch and a typical “wedged” tracing appears (Fig. 16-1D).
平均 15 mmHg ）（图 16-1C）。最后，导管进一步进入肺动脉，直到其尖端被球囊包围，撞击较小的分支，并出现典型的“楔形”轨迹（图 16-1D）。
Several tips may facilitate passage of a pulmonary artery catheter. A number 7 French catheter is easier to pass than are smaller sizes, its greater stiffness preventing kinking and its larger lumen providing better quality tracings. The right lateral position may facilitate entry into the pulmonary outflow tract. Because catheter material can soften at body temperature, squirting a small quantity of iced saline through the lumen may restore enough stiffness to complete passage if this has taken longer than about 10 minutes. If a digital readout is used in guiding insertion, the “systole” reading should be used when passing from right atrium to right ventricle, the “diastole” reading when in the right ventricle, and “systole” again when attempting to wedge the catheter tip. The distance from ventricle to pulmonary artery outflow tract is not
有几个技巧可能有助于肺动脉导管的通过。7 号法式导管比较小尺寸的导管更容易通过，其更大的刚度可防止扭结，较大的管腔提供更高质量的描记。右侧卧位可能有助于进入肺流出道。由于导管材料在体温下会软化，因此如果喷洒时间超过约 10 分钟，通过管腔喷洒少量冰盐水可能会恢复足够的刚度以完成排尿。如果使用数字读数引导插入，则从右心房通过右心室时应使用“收缩”读数，在右心室时应使用“舒张”读数，当试图楔入导管尖端时应再次使用“收缩”读数。从心室到肺动脉流出道的距离不是
more than 15 cm , so the catheter should be withdrawn and another pass made if more than this has been advanced in the attempt. When the catheter is in the pulmonary artery, a wedge position should be achieved within 8 to 10 cm . The insertion of approximately 0.8 ml of air into the balloon should be all that is required to wedge the catheter.
超过 15 厘米，因此应在尝试中推进超过此长度，并再次通过。当导管位于肺动脉中时，应在 8 至 10 cm 内达到楔形位置。只需将大约 0.8 ml 空气插入球囊即可楔入导管。

Fluoroscopy can be of considerable help during catheter passage but is usually not necessary. When the procedure is complete and the catheter tip has been withdrawn from the wedge position to prevent ischemia and thrombosis in the distal vessel, a portable chest roentgenogram should be obtained promptly to confirm appropriate placement and to assure that no pneumothorax has occurred. If the catheter tip is more than about 3 cm beyond the hilum, an increased chance of pulmonary infarction develops, and the tip should be pulled back. This may not be required if the catheter continues to wedge with a

0.8 - ml

volume.
透视在导管通过期间有很大帮助，但通常不是必需的。当手术完成并且导管尖端已从楔形位置撤出以防止远端血管缺血和血栓形成时，应立即进行便携式胸部 X 线片检查，以确认放置适当并确保未发生气胸。如果导管尖端超出肺门约 3 cm，则肺梗死的机会会增加，应将尖端向后拉。如果导管继续楔入

0.8 - ml

体积，则可能不需要这样做。

Catheters usually go to areas with the greatest flow, which in a supine patient means into a pulmonary artery directed posteriorly. They are thus usually placed in a lung region in which vascular pressures are always greater than airway pressures and the catheter “sees” pulmonary arterial or Ppaw pressure as intended. Sometimes, however, the catheter may rest in a pulmonary artery whose flow is interrupted by the surrounding airway (alveolar) pressure during all or part of the respiratory cycle. This is more likely to occur during PEEP therapy or in the presence of severe obstructive lung disease or hypovolemia. In such circumstances the pressures registered from the catheter reflect alveolar pressure and may be erroneously high. This can usually be detected by examining the pressure tracing (rather than just a digital readout) for the characteristic vascular patterns (see Fig. 16-1). A significant respiratory variation should be present if the catheter is measuring alveolar pressure. If there is a suspicion of malpositioning of the catheter as described here, a cross-bed lateral roentgenogram, taken with the patient in the same position in which pressure readings were obtained, will clarify the catheter’s location in the chest’s anteriorposterior dimension. It is more likely to give artifactual readings if it lies above the level of the left atrium.
导管通常通向流量最大的区域，在仰卧位患者中，这意味着进入向后定向的肺动脉。因此，它们通常被放置在血管压力始终大于气道压力的肺部区域，并且导管按预期“看到”肺动脉或 Ppaw 压力。然而，有时导管可能位于肺动脉中，在全部或部分呼吸周期中，肺动脉的流动被周围的气道（肺泡）压力中断。这更可能发生在 PEEP 治疗期间或存在严重阻塞性肺病或低血容量的情况下。在这种情况下，从导管记录的压力反映了肺泡压力，并且可能错误地很高。这通常可以通过检查特征性血管模式的压力追踪（而不仅仅是数字读数）来检测（见图 16-1）。如果导管测量肺泡压，则应存在显着的呼吸变化。如果怀疑如此处所述的导管错位，则与患者在获得压力读数的相同位置拍摄的跨床侧位线片将阐明导管在胸部前后维度中的位置。如果它位于左心房的水平以上，则更有可能给出伪影读数。

These factors can help to confirm that a pulmonary artery catheter is “wedged.” In this position, the phasic pulmonary artery tracing flattens into a characteristic left atrial pattern. The mean Ppaw is lower than mean pulmonary artery pressure. Also, blood aspirated very slowly from the catheter in the “wedge” position should be fully saturated pulmonary venous blood. This last rule, however, may not hold in the presence of ARDS.
这些因素可以帮助确认肺动脉导管是“楔形的”。在这个位置，阶段性肺动脉轨迹变平，形成特征性的左心房模式。平均 Ppaw 低于平均肺动脉压。此外，从“楔形”位置的导管中非常缓慢地吸出的血液应该是完全饱和的肺静脉血。然而，这最后一条规则在存在 ARDS 的情况下可能不成立。

Interpretation. Several practical factors are crucial to obtaining meaningful information from a pulmonary artery catheter. The pressures measured are dynamic, not static, and the values used should be the average of at least two separate readings. Wedge
解释。几个实际因素对于从肺动脉导管获得有意义的信息至关重要。测得的压力是动态的，而不是静态的，使用的值应该是至少两个单独读数的平均值。楔

le, le, to the same (left atrial) level on the patient’s chest every time, and reading of the Ppaw from a calibrated tracing, rather than a digital readout, in order to be sure the numbers are not artifactual.

le， le，每次都调整到患者胸部的相同（左心房）水平，并从校准的描记而不是数字读数中读取 Ppaw，以确保这些数字不是人为的。

Measurements of vascular pressures, and especially Ppaw during therapy with PEEP, are an area of confusion and controversy. A common question is whether a PPAW value obtained during PEEP accurately reflects true intracavitary left atrial pressure. The answer is that it does, so long as the pressure tracing shows the characteristic “wedge” pattern. But does it correspond to what the Ppaw would be without the PEEP? Probably not, because PEEP physiologically alters intrathoracic hemodynamics. If taken off PEEP the patient would quickly manifest a different set of cardiovascular and airway pressures reflecting increased venous return to the thorax and other changes; these too would be accurate if correctly measured, but they would not necessarily reflect the situation present during PEEP. It seems most reasonable to measure the pressures that apply to the patient during therapy rather than during a brief interval without it, and for this reason mechanical ventilation or PEEP is not discontinued when making measurements.
血管压的测量，尤其是 PEEP 治疗期间的 Ppaw 测量，是一个令人困惑和争议的领域。一个常见的问题是，在 PEEP 期间获得的 PPAW 值是否准确反映了真实的左心房内压。答案是它确实如此，只要压力轨迹显示特征性的“楔形”模式。但它是否对应于没有 PEEP 的 Ppaw 是什么样子呢？可能不会，因为 PEEP 在生理上会改变胸腔内血流动力学。如果脱离 PEEP，患者将很快表现出一组不同的心血管和气道压力，反映静脉回流到胸部的增加和其他变化;如果测量正确，这些也是准确的，但它们不一定反映 PEEP 期间出现的情况。在治疗期间测量施加在患者身上的压力似乎是最合理的，而不是在没有治疗时的短暂间隔内测量，因此在进行测量时不会停止机械通气或 PEEP。

The amount of PEEP should not be subtracted from the Ppaw reading. Instead, a valid rule of thumb for estimating the effect of PEEP is to assume that approximately one-half the PEEP is transmitted to the left atrium, or about 1.5 mmHg for every 5 cm

H_{2} O

of PEEP. Because Ppaw is usually measured in millimeters of mercury and PEEP in centimeters of water, both must be seen in the same units. Thus, about half of the converted PEEP magnitude is then subtracted from the Praw reading to give an approximation of true intracavitary left atrial distending pressure. As an example, if in a given patient on

20 cm H_{2} O PEEP

, a Ppaw reading of 26 mmHg is obtained, subtracting 6 mmHg ( 1.5 mm

Hg / 5 cm H

, O PEEP) yields an intracavitary true left atrial pressure of 19 mmHg . When PEEP is increased, the measured PPAw should never increase by more than half the amount; if this happens, airway pressure is probably being detected rather than left atrial pressure.
不应从 Ppaw 读数中减去 PEEP 的量。相反，估计 PEEP 效果的有效经验法则是假设大约一半的 PEEP 传输到左心房，或每 5 cm

H_{2} O

PEEP 约 1.5 mmHg。因为 Ppaw 通常以毫米汞柱为单位，PEEP 以厘米水为单位，所以两者必须以相同的单位显示。因此，然后从 Praw 读数中减去大约一半的转换 PEEP 幅度，以得出真实腔内左心房扩张压的近似值。例如，如果在给定的患者中

20 cm H_{2} O PEEP

，获得的 Ppaw 读数为 26 mmHg，减去 6 mmHg（1.5 mm，O

Hg / 5 cm H

PEEP）得出腔内真实左心房压为 19 mmHg。当 PEEP 增加时，测得的 PPAw 增加不应超过量的一半;如果发生这种情况，则可能是检测到气道压迫，而不是左心房压。

Measurement of Ppaw in patients with severe airflow obstruction is technically difficult to perform with accuracy because of coexistent wide intrathoracic pressure swings when these patients breathe vars to . reading may simply not be possible. useful data collection are careful zeroing of the pressure transducer
在严重气流阻塞患者中测量 Ppaw 在技术上很难准确进行，因为当这些患者呼吸时，胸腔内压力波动较大。阅读可能根本不可能。有用的数据收集是将压力传感器仔细归零
pressures should not be recorded until distal venous runoff ceases, which may take 5 to 10 seconds in some patients. The Ppaw should be measured at the same point in the respiratory cycle each time (end-expiration is best, as there are no superimposed pressures and it is easily identified). Also, the patient should always be in the same position, although elevation of the backrest to 20 degrees does not affect the measurement. Uncontrollable agitation renders pressure readings erroneous, and in such situations a valid Ppaw
在远端静脉径流停止之前不应记录压力，某些患者可能需要 5 到 10 秒。每次应在呼吸周期的同一点测量 Ppaw（呼气末是最好的，因为没有叠加的压力并且很容易识别）。此外，患者应始终处于同一位置，尽管将靠背抬高 20 度不会影响测量。无法控制的搅动会导致压力读数错误，在这种情况下，有效的 Ppaw

1

r .
: ct . ： ct .

医学博士

. .

部

spontaneously. Readings should be made at end-expiration, and the mean of several separate measurements should be used. In addition, “auto PEEP” should be looked for and the wedge pressure corrected in the same manner used for PEEP. In some patients with agitation or severe distress, valid PPAW measurements simply cannot be made until these resolve or improve.
自发性。应在到期时进行读数，并应使用几次单独测量的平均值。此外，应寻找“自动 PEEP”，并以与 PEEP 相同的方式校正楔形压力。在一些有激越或严重痛苦的患者中，在这些消退或改善之前根本无法进行有效的 PPAW 测量。
Fluid Challenge. The pulmonary artery catheter makes possible the direct assessment of circulatory dynamics in patients whose volume status is unclear. However, a single measurement may not completely clarify the issue. In such instances a fluid challenge can be employed as a monitoring tool. Having assessed the patient’s cardiovascular function as extensively as the clinical situation dictates-by using MAP, urine output, Ppaw, and thermodilution QT-the clinician rapidly infuses a bolus of fluid, usually 50 to 200 ml over 15 to 20 minutes, and repeats the assessment after 5 to 10 minutes. Using this procedure the appropriate fluid therapy for the individual patient can be judged according to the response elicited. An abrupt rise in Ppaw of 5 to 7 mmHg or more, or the onset of dyspnea, signals excessive fluid administration, whereas an improvement in the parameters measured, along with a lesser increment in PPAW, suggests that the infusion of more fluid will further improve circulatory dynamics.
流体挑战。肺动脉导管可以直接评估容量状态不明患者的循环动力学。但是，单个测量可能无法完全阐明问题。在这种情况下，可以采用液体激发试验作为监测工具。根据临床情况，通过使用 MAP、尿量、Ppaw 和热稀释 QT 对患者的心血管功能进行了最广泛的评估后，临床医生迅速推注液体，通常在 15 至 20 分钟内输注 50 至 200 毫升，并在 5 至 10 分钟后重复评估。使用该程序，可以根据引发的反应判断适合个体患者的液体治疗。Ppaw 突然升高 5 至 7 mmHg 或更高，或呼吸困难的发作，表明液体给药过多，而测量参数的改善以及 PPAW 的增加较小，表明注入更多的液体将进一步改善循环动力学。
Complications. Numerous complications can result from the insertion, maintenance, and use of a pulmonary artery catheter. Perhaps the most frequent of these are the generation of erroneous, artifactual, or improperly collected data and the misuse of good data by staff who do not fully understand the measurements. These detriments to good patient care can be eliminated by scrupulous attention to technique and thorough familiarity with the physiology underlying the use of underlying the use of the catheter. Several other complications occur, including bleeding, infection, pneumothorax, and local trauma to nerves and other tissues at the insertion site. Once inside the thorax, a catheter can produce serious dysrhythmias, air embolism, direct valve damage, laceration or rupture of a pulmonary artery, and pulmonary infarction distal to a catheter left too long in the wedged position. Familiarity with these and other potential complications will help decrease the likelihood of their occurrence.
并发症。插入、维护和使用肺动脉导管可导致许多并发症。其中最常见的可能是产生错误、人为或收集不当的数据，以及不完全了解测量结果的工作人员滥用优质数据。通过对技术的严格关注和对导管使用基础的生理机能的彻底熟悉，可以消除这些对良好患者护理的危害。还会发生其他几种并发症，包括出血、感染、气胸以及插入部位神经和其他组织的局部创伤。一旦进入胸腔，导管会产生严重的心律失常、空气栓塞、直接瓣膜损伤、肺动脉撕裂伤或破裂，以及导管在楔形位置停留时间过长的远端肺梗死。熟悉这些并发症和其他潜在并发症将有助于降低它们发生的可能性。

Infection at the catheter insertion site can be minimized if special effort is made to keep the area sterile. Dressings should be changed daily. As a general principle, a pulmonary artery catheter should be removed or changed in 72 hours; lack of other access sites may occasionally demand extension of this period, although this may increase the risk of infection.
如果特别努力保持导管插入部位的无菌，则可以最大限度地减少导管插入部位的感染。敷料应每天更换。作为一般原则，应在 72 小时内拔除或更换肺动脉导管;缺乏其他访问站点可能偶尔需要延长此期限，尽管这可能会增加感染风险。

MONITORING TISSUE OXYGENATION
监测组织氧合

Therapy to improve tissue oxygenation (see Chapter 14) is aimed at providing a steady supply of

O_{2}

to the tissues that is adequate
改善组织氧合的疗法（见第 14 章）旨在为组织提供足够的稳定供应

O_{2}

for their metabolic needs. According to the Fick equation, these needs-the

{VO}_{2}

-are the product of QT and the peripheral

O_{2}

extraction,

{CaO}_{2} - C \overset{―}{\bar{v}} O_{2}

C (a - \overset{―}{\bar{v}}) O_{2}

. Oxygen supply-

O_{2}

trans-port-is identified by the terms QT and

{CaO}_{2}

in this equation. The Fick equation predicts that Qt,

C (a - \overset{―}{v}) O_{2}

, or both must increase to maintain an increasing

{VO}_{2}

. It has been assumed, therefore, that

O_{2}

supply is set by

O_{2}

demand.
满足他们的新陈代谢需求。根据 Fick 方程，这些需求 - 是

{VO}_{2}

QT 和外围

O_{2}

提取的乘积，

{CaO}_{2} - C \overset{―}{\bar{v}} O_{2}

或

C (a - \overset{―}{\bar{v}}) O_{2}

。氧气供应 -

O_{2}

转位 - 由术语 QT 和

{CaO}_{2}

该方程式标识。Fick 方程预测 Qt、

C (a - \overset{―}{v}) O_{2}

或两者必须增加才能保持增加

{VO}_{2}

。因此，人们假设

O_{2}

供应是由

O_{2}

需求决定的。

In keeping with this assumption, the

C (a - \overset{―}{v}) O_{2}

or the

C \overset{―}{v} O_{2}

has been used as an indicator of the adequacy of tissue oxygenation. Even more popular indicators are the

{PO}_{2}

of mixed venous blood

({Pv}_{2} O_{2})

and the mixed venous

O_{2}

saturation (

S \overset{―}{v} O_{2}

) obtain pulmonary artery catheterizations. It generally is 2 cebtained by purped from the normal leved accepted that a marked decine 75 per cent indicates inadequal level of 40 mmHg or an

{SaO}_{2}

below 75 per cention. This inadequacy is attributed to the

{CaO}_{2}

and especially the QT , because it is believed that the peripheral tissues are extracting more

O_{2}

from their diminished supply of oxygenated blood. In fact, the

P \overset{―}{v} O_{2}

and

S \overset{―}{v} O_{2}

frequently are used to estimate QT, especially when thermodilution techniques are not available.
与此假设一致，或

C (a - \overset{―}{v}) O_{2}

已

C \overset{―}{v} O_{2}

用作组织氧合充分性的指标。更流行的指标是

{PO}_{2}

混合静脉血

({Pv}_{2} O_{2})

和混合静脉

O_{2}

饱和度（

S \overset{―}{v} O_{2}

）获得肺动脉导管插入术。它通常是 2 cebtain，从正常征税中抽离出来，公认的 75% 表示 40 mmHg 或

{SaO}_{2}

低于 75% 的不等水平。这种不足归因于

{CaO}_{2}

QT ，尤其是 QT ，因为人们认为外周组织从其减少的含氧血液供应中提取了更多

O_{2}

。事实上，和

P \overset{―}{v} O_{2}

S \overset{―}{v} O_{2}

经常用于估计 QT，尤其是在热稀释技术不可用时。

Although this is appropriate in many patients, it may not apply to those with severe ARDS. Recent studies have shown that VO, varies directly with

\dot{Q T}

and

{CaO}_{2}

in certain patients with ARDS; in other words,

{VO}_{2}

may be set by

O_{2}

supply rather than vice versa. As a result, in these individuals,

C (a - \overset{―}{v}) O_{2}

may not vary with changes in QT to the degree expected if

{VO}_{2}

remains constant, especially in the setting of a very low Qt. The mechanisms accounting for these findings are not clear, although alterations in regional blood flow or

O_{2}

extraction or both may be responsible. It also is not clear whether the findings are due to ARDS, to PEEP, or to both. Nevertheless, the link between

O_{2}

supply and demand implies that the CüO demand implies that the

{Cv}_{2} O_{2}, P \overset{―}{v} O_{2}

, and

S \overset{―}{v} O_{2}

may not accurately reflect the adequacy of tissue oxygenation in patients with severe ARDS. Of course, the same is true in cyanide poisoning, in which severe tissue hypoxia exists in the presence of an elevated

P_{\overset{―}{v}} O_{2}

, owing to a paralysis of intracellular respiration.
虽然这适用于许多患者，但可能不适用于重度 ARDS 患者。最近的研究表明，VO 与某些 ARDS 患者直接

\dot{Q T}

{CaO}_{2}

不同;换句话说，

{VO}_{2}

可以由

O_{2}

Supply 设置，而不是相反。因此，在这些个体中，

C (a - \overset{―}{v}) O_{2}

如果

{VO}_{2}

保持不变，可能不会随 QT 的变化而变化到预期的程度，尤其是在 Qt 非常低的情况下。解释这些发现的机制尚不清楚，尽管区域血流或

O_{2}

拔出物的改变或两者的改变可能是原因。目前也不清楚这些发现是由于 ARDS、PEEP 还是两者兼而有之。然而，供需之间的

O_{2}

联系意味着 CüO 需求意味着

{Cv}_{2} O_{2}, P \overset{―}{v} O_{2}

，并且

S \overset{―}{v} O_{2}

可能无法准确反映严重 ARDS 患者组织氧合的充分性。当然，氰化物中毒也是如此，其中严重的组织缺氧存在于升高

P_{\overset{―}{v}} O_{2}

，由于细胞内呼吸麻痹。

Given the limitations of the

P_{\overset{―}{v}} O_{2}

, what is the optimal indicator of tissue oxygenation? Ideally, the clinician requires some measurement of tissue activity or performance: lactate to pyruvate ratios from key tissue beds as reflections of alveolar metabolism, for example, or sophisticated tests of brain function. Yet these are not generally available. Until they are, the clinician must assess all hemodynamic and clinical data in concert with simple bedside observation, including a careful mental status exam.
鉴于的

P_{\overset{―}{v}} O_{2}

局限性，组织氧合的最佳指标是什么？理想情况下，临床医生需要对组织活动或性能进行一些测量：例如，来自关键组织床的乳酸与丙酮酸比率作为肺泡代谢的反映，或脑功能的复杂测试。然而，这些并非普遍可用。在此之前，临床医生必须评估所有血流动力学和临床数据，并进行简单的床旁观察，包括仔细的精神状态检查。

HOME RESPIRATORY CARE 家庭呼吸护理

Home care is the provision of health care services in a patient’s home rather than in the hospital or a physician’s office. Respiratory home care has assumed an increasingly important role as stricter reimbursement policies have shortened hospital stays and the costeffectiveness of managing patients in their own homes has been documented. In-home management of sicker, often technologydependent patients has led to development of sophisticated home care delivery systems and the emergence of the respiratory home care specialist-usually a respiratory care practitioner (respiratory therapist)-as a key liaison between physicians and patients. Unfortunately, to date the training of physicians in current respiratory home care practice has lagged behind that offered to nurses and respiratory care practitioners.
家庭护理是在患者家中而不是在医院或医生办公室提供医疗保健服务。随着更严格的报销政策缩短了住院时间，并且已经记录了在自己家中管理患者的成本效益，呼吸家庭护理发挥着越来越重要的作用。对病情较重、通常依赖技术的患者进行家庭管理，导致了复杂的家庭护理服务系统的发展，以及呼吸家庭护理专家的出现——通常是呼吸护理从业者（呼吸治疗师）——作为医生和患者之间的关键联络人。不幸的是，迄今为止，当前呼吸家庭护理实践中医生的培训落后于为护士和呼吸护理从业者提供的培训。

Although the field includes an expanding array of treatments and home care services, this chapter focuses on four: long-term oxygen therapy (for treatment of chronic hypoxemia and cor pulmonale), long-term ventilatory assistance (for individuals unable to breathe spontaneously or to rest the ventilatory muscles in patients with chronic respiratory insufficiency), nocturnal continuous positive airway pressure (for management of obstructive sleep apnea), and pulmonary rehabilitation (to increase functional capability in patients with a variety of chronic respiratory disorders). Information on other aspects of respiratory home care, as well as more comprehensive coverage of the modalities discussed here, can be found in the recommended reading listed at the end of this chapter.
尽管该领域包括越来越多的治疗和家庭护理服务，但本章重点介绍四项：长期氧疗（用于治疗慢性低氧血症和肺心病）、长期通气辅助（用于慢性呼吸功能不全患者无法自主呼吸或无法休息通气肌的个体）、夜间持续气道正压通气（用于管理阻塞性睡眠呼吸暂停）、和肺康复（提高患有各种慢性呼吸系统疾病的患者的功能能力）。有关呼吸系统家庭护理其他方面的信息，以及此处讨论的方式的更全面覆盖，可以在本章末尾列出的推荐阅读材料中找到。

LONG-TERM OXYGEN THERAPY 长期氧疗

THERAPEUTIC RATIONALE 治疗原理

Supplemental oxygen therapy is administered to hospitalized, acutely ill, hypoxemic patients to restore adequate tissue oxygenation and to prevent cardiac dysrhythmias and other potentially
对住院、急性病、低氧血症患者进行补充氧疗，以恢复足够的组织氧合并预防心律失常和其他潜在的

WEANING 断乳

WEANING FROM MECHANICAL VENTILATION机械通气脱机

DEFINITION 定义

ASSESSMENT FOR WEANING 脱机评估

Oxygenation 氧合

Ventilatory Demand 通气需求

Ventilatory Mechanics 通气力学

TRADITIONAL VENTILATOR WEANING传统呼吸机脱机

Rationale 理由

Picking the Right Time 选择合适的时间

Technique 技术

Table 15-1. TRADITIONAL WEANING PROTOCOL表 15-1.传统脱机方案

Gradual Traditional Weaning渐进式传统断奶

WEANING WITH INTERMITTENT MANDATORY VENTILATION间歇性指令通气脱机

Rationale 理由

Picking the Right Time 选择合适的时间

Technique 技术

Gradual IMV Weaning 渐进式 IMV 脱机

WEANING WITH PRESSURE SUPPORT使用压力支持脱机

Rationale 理由

Picking the Right Time 选择合适的时间

Technique 技术

FAILURE TO WEAN 脱机失败

Definition 定义

Weakness 弱点

Insufficient Ventilatory Drive通气驱动不足

Excessive Work of Breathing过度呼吸功

High Ve Requirement 高 Ve 要求

WEANING FROM ENDOTRACHEAL INTUBATION气管插管脱机

DEFINITION 定义

PREDICTORS OF SUCCESS 成功的预测因素

TECHNIQUE 技术

RECOMMENDED READING 推荐阅读

MONITORING THE PATIENT 监测患者

INTENSIVE CARE MONITORING重症监护监测

WHAT TO MONITOR, AND WHY要监控的内容和原因

MONITORING WITHOUT MACHINERY无需机械即可进行监控

THE CHEST ROENTGENOGRAM AS A MONITORING TOOL胸部 X 线片作为监测工具

248 / MONITORING THE PATIENT248 / 监测病人

MONITORING VENTILATORY MECHANICS监测通气力学

Respiratory Rate 呼吸频率

Lung Volumes 肺容量

Respiratory System Compliance呼吸系统顺应性

Flow Rates 流速

Respiratory Muscle Function呼吸肌功能

MONITORING GAS EXCHANGE 监测气体交换

Alveolar Ventilation 肺泡通气

pH 酸碱度

MONITORING OXYGEN TRANSPORT监测氧气运输

General Considerations 一般注意事项

Arterial Oxygen Content 动脉血氧含量

Cardiac Output 心输出量

256 / MONITORING THE PATIENT256 / 监测病人

INVASIVE HEMODYNAMIC MONITORING TECHNIQUES有创血流动力学监测技术

Arterial Catheters 动脉导管

Central Venous Catheters 中心静脉导管

Balloon-Tipped Pulmonary Artery (Swan-Ganz) Catheters球囊尖端肺动脉 （Swan-Ganz） 导管

MONITORING TISSUE OXYGENATION监测组织氧合

RECOMMENDED READING 推荐阅读

HOME RESPIRATORY CARE 家庭呼吸护理

LONG-TERM OXYGEN THERAPY 长期氧疗

THERAPEUTIC RATIONALE 治疗原理

WEANING FROM MECHANICAL VENTILATION
机械通气脱机

TRADITIONAL VENTILATOR WEANING
传统呼吸机脱机

Table 15-1. TRADITIONAL WEANING PROTOCOL
表 15-1.传统脱机方案

Gradual Traditional Weaning
渐进式传统断奶

WEANING WITH INTERMITTENT MANDATORY VENTILATION
间歇性指令通气脱机

WEANING WITH PRESSURE SUPPORT
使用压力支持脱机

Insufficient Ventilatory Drive
通气驱动不足

Excessive Work of Breathing
过度呼吸功

WEANING FROM ENDOTRACHEAL INTUBATION
气管插管脱机

INTENSIVE CARE MONITORING
重症监护监测

WHAT TO MONITOR, AND WHY
要监控的内容和原因

MONITORING WITHOUT MACHINERY
无需机械即可进行监控

THE CHEST ROENTGENOGRAM AS A MONITORING TOOL
胸部 X 线片作为监测工具

248 / MONITORING THE PATIENT
248 / 监测病人

MONITORING VENTILATORY MECHANICS
监测通气力学

Respiratory System Compliance
呼吸系统顺应性

Respiratory Muscle Function
呼吸肌功能

MONITORING OXYGEN TRANSPORT
监测氧气运输

256 / MONITORING THE PATIENT
256 / 监测病人

INVASIVE HEMODYNAMIC MONITORING TECHNIQUES
有创血流动力学监测技术

Balloon-Tipped Pulmonary Artery (Swan-Ganz) Catheters
球囊尖端肺动脉（Swan-Ganz）导管

MONITORING TISSUE OXYGENATION
监测组织氧合