Bikker Ido G, van Bommel Jasper, Reis Miranda Dinis, Bakker Jan, Gommers Diederik
Department of Intensive Care Medicine, Erasmus MC, 's Gravendijkwal 230, 3015 CERotterdam, The Netherlands.
Crit Care. 2008;12(6):R145. doi: 10.1186/cc7125. Epub 2008 Nov 20.
Functional residual capacity (FRC) reference values are obtained from spontaneous breathing patients, and are measured in the sitting or standing position. During mechanical ventilation FRC is determined by the level of positive end-expiratory pressure (PEEP), and it is therefore better to speak of end-expiratory lung volume. Application of higher levels of PEEP leads to increased end-expiratory lung volume as a result of recruitment or further distention of already ventilated alveoli. The aim of this study was to measure end-expiratory lung volume in mechanically ventilated intensive care unit (ICU) patients with different types of lung pathology at different PEEP levels, and to compare them with predicted sitting FRC values, arterial oxygenation, and compliance values.
End-expiratory lung volume measurements were performed at PEEP levels reduced sequentially (15, 10 and then 5 cmH2O) in 45 mechanically ventilated patients divided into three groups according to pulmonary condition: normal lungs (group N), primary lung disorder (group P), and secondary lung disorder (group S).
In all three groups, end-expiratory lung volume decreased significantly (P < 0.001) while PEEP decreased from 15 to 5 cmH2O, whereas the ratio of arterial oxygen tension to inspired oxygen fraction did not change. At 5 cmH2O PEEP, end-expiratory lung volume was 31, 20, and 17 ml/kg predicted body weight in groups N, P, and S, respectively. These measured values were only 66%, 42%, and 34% of the predicted sitting FRC. A correlation between change in end-expiratory lung volume and change in dynamic compliance was found in group S (P < 0.001; R2 = 0.52), but not in the other groups.
End-expiratory lung volume measured at 5 cmH2O PEEP was markedly lower than predicted sitting FRC values in all groups. Only in patients with secondary lung disorders were PEEP-induced changes in end-expiratory lung volume the result of derecruitment. In combination with compliance, end-expiratory lung volume can provide additional information to optimize the ventilator settings.
功能残气量（FRC）参考值来自自主呼吸患者，且是在坐位或站立位测量的。在机械通气期间，FRC由呼气末正压（PEEP）水平决定，因此更确切地说是呼气末肺容积。应用较高水平的PEEP会因已通气肺泡的复张或进一步扩张而导致呼气末肺容积增加。本研究的目的是测量不同类型肺部病变的机械通气重症监护病房（ICU）患者在不同PEEP水平下的呼气末肺容积，并将其与预测的坐位FRC值、动脉氧合及顺应性值进行比较。
对45例机械通气患者按肺部情况分为三组：正常肺组（N组）、原发性肺部疾病组（P组）和继发性肺部疾病组（S组），依次将PEEP水平降至15、10然后5 cmH₂O时测量呼气末肺容积。
在所有三组中，当PEEP从15 cmH₂O降至5 cmH₂O时，呼气末肺容积显著降低（P < 0.001），而动脉血氧分压与吸入氧分数之比未改变。在5 cmH₂O PEEP时，N组、P组和S组的呼气末肺容积分别为预测体重的31、20和17 ml/kg。这些测量值仅为预测坐位FRC的66%、42%和34%。S组中发现呼气末肺容积变化与动态顺应性变化之间存在相关性（P < 0.001；R² = 0.52），但其他组未发现。
在所有组中，5 cmH₂O PEEP时测量的呼气末肺容积均明显低于预测的坐位FRC值。仅在继发性肺部疾病患者中，PEEP引起的呼气末肺容积变化是肺泡萎陷的结果。结合顺应性，呼气末肺容积可为优化呼吸机设置提供额外信息。
Zotero 插件
