Rossi A, Santos C, Roca J, Torres A, Félez M A, Rodriguez-Roisin R
Servei de Pneumologia i Allérgia Respiratòria, Hospital Clínic, Universitat de Barcelona, Spain.
Am J Respir Crit Care Med. 1994 May;149(5):1077-84. doi: 10.1164/ajrccm.149.5.8173744.
Recent work in patients with acute respiratory failure (ARF) due to exacerbation of chronic airflow obstruction (CAO) suggests that application of low degrees of positive end-expiratory pressure (PEEP) can improve rather than impair respiratory mechanics, because PEEP replaces intrinsic PEEP (PEEPi). However, the impact of PEEP on pulmonary gas exchange has not been fully investigated. We designed this study to examine the effects of PEEP and those of PEEPi on ventilation/perfusion (VA/Q) mismatching in mechanically ventilated patients with CAO. Eight patients were studied under four conditions: (1) during controlled mechanical ventilation with the ventilatory setting established by the attending physicians (PEEPi-100%), according to standard criteria; (2) after application of PEEP amounting to 50% (PEEP-50%), and then (3) to 100% (PEEP-100%) of the original PEEPi; and finally, (4) after reduction of PEEPi to 50% of the initial value (PEEPi-50%), obtained by increasing expiratory time and decreasing respiratory rate and tidal volume. Respiratory mechanics, hemodynamics, respiratory blood gases, and VA/Q distributions were measured during each ventilatory mode. At low values of PEEP (PEEP-50%) no changes in respiratory mechanics nor in hemodynamics were observed, but PaO2 moderately increased (from 103 +/- 25.2 to 112 +/- 29.6 mm Hg) and PaCO2 slightly decreased (from 42 +/- 3.7 to 40 +/- 3.3 mm Hg) essentially because of an increase in the mean VA/Q ratio (first moment) of both flood flow (Q, from 0.65 +/- 0.28 to 0.78 +/- 0.29) and ventilation (V, from 4.02 +/- 1.55 to 4.93 +/- 2.00) distributions (p < 0.05, each).(ABSTRACT TRUNCATED AT 250 WORDS)
近期针对因慢性气流阻塞（CAO）急性加重导致急性呼吸衰竭（ARF）患者的研究表明，应用低水平呼气末正压（PEEP）可改善而非损害呼吸力学，因为PEEP替代了内源性PEEP（PEEPi）。然而，PEEP对肺气体交换的影响尚未得到充分研究。我们设计本研究以探讨PEEP及PEEPi对机械通气的CAO患者通气/灌注（VA/Q）不匹配的影响。对8例患者在四种情况下进行了研究：（1）根据标准标准，在主治医师设定的通气参数下进行控制机械通气时（PEEPi-100%）；（2）应用相当于原始PEEPi 50%的PEEP后（PEEP-50%），然后（3）应用至原始PEEPi的100%（PEEP-100%）；最后，（4）通过延长呼气时间、降低呼吸频率和潮气量，将PEEPi降至初始值的50%后（PEEPi-50%）。在每种通气模式下测量呼吸力学、血流动力学、呼吸血气及VA/Q分布。在低水平PEEP（PEEP-50%）时，未观察到呼吸力学及血流动力学的变化，但PaO2适度升高（从103±25.2升至112±29.6 mmHg），PaCO2略有下降（从42±3.7降至40±3.3 mmHg），这主要是由于肺血流量（Q，从0.65±0.28升至0.78±0.29）和通气量（V，从4.02±1.55升至4.93±2.00）分布的平均VA/Q比值（一阶矩）增加所致（各p<0.05）。（摘要截短于250词）
