Zakynthinos S G, Vassilakopoulos T, Zakynthinos E, Roussos C
Dept of Critical Care and Pulmonary Services, Athens University Medical School, Evangelismos Hospital, Greece.
Eur Respir J. 1997 Mar;10(3):522-9.
It has been shown that expiratory muscle contraction leads to an overestimation of intrinsic positive end-expiratory pressure (PEEPi). To quantify this overestimation, we compared PEEPi, measured during spontaneous breathing (SB) by the end-expiratory airway occlusion technique (PEEPi,occl) with static PEEPi (PEEPi,st). PEEPi,st was measured using end-expiratory airway occlusion during simulation of SB by the ventilator with the patient relaxed, and was considered to represent the "gold standard" for PEEPi,occl. Twelve ventilator-dependent patients were studied during SB (pressure support 5-7 cmH2O). Full mechanical ventilation was resumed when they were unable to sustain SB. Subsequently, by manipulating the variables of the ventilator, we simulated the pattern of SB and measured PEEPi,st, corresponding to PEEPi,occl. On the basis of the presence or absence of expiratory rise in gastric pressure (Pga) (rapid drop of end-expiratory Pga at the beginning of inspiration, Pga,exp,rise), and abdominal muscle electromyographic (EMG) activity, patients were subdivided into those either actively (Group 1) or passively expiring (Group 2). In Group 1 (8 patients), PEEPi,occl was higher than PEEPi,st (13.3+/-2.0 vs 6.8+/-1.1 cmH2O; p<0.01). PEEPi,occl-Pga,exp,rise (6.9+/-1.1 cmH2O) was quite similar to PEEPi,st; their mean difference was 0.03 cmH2O with limits of agreement -0.48 to +0.53 cmH2O. In Group 2, PEEPi,occl was similar to PEEPi,st. We conclude that, in actively expiring patients, an accurate estimation of the actual PEEPi,st can be obtained by subtracting Pga,exp,rise from PEEPi,occl.
研究表明，呼气肌收缩会导致对内在呼气末正压（PEEPi）的高估。为了量化这种高估，我们将通过呼气末气道阻断技术在自主呼吸（SB）期间测量的PEEPi（PEEPi,occl）与静态PEEPi（PEEPi,st）进行了比较。PEEPi,st是在患者放松状态下由呼吸机模拟SB期间通过呼气末气道阻断测量的，被视为PEEPi,occl的“金标准”。对12例依赖呼吸机的患者在SB期间（压力支持5 - 7 cmH2O）进行了研究。当他们无法维持SB时恢复完全机械通气。随后，通过操纵呼吸机变量，我们模拟了SB模式并测量了与PEEPi,occl相对应的PEEPi,st。根据胃内压（Pga）呼气时是否升高（吸气开始时呼气末Pga快速下降，Pga,exp,rise）以及腹肌肌电图（EMG）活动，将患者分为主动呼气组（第1组）或被动呼气组（第2组）。在第1组（8例患者）中，PEEPi,occl高于PEEPi,st（13.3±2.0 vs 6.8±1.1 cmH2O；p<0.01）。PEEPi,occl - Pga,exp,rise（6.9±1.1 cmH2O）与PEEPi,st非常相似；它们的平均差异为0.03 cmH2O，一致性界限为 - 0.48至 + 0.53 cmH2O。在第2组中，PEEPi,occl与PEEPi,st相似。我们得出结论，在主动呼气的患者中，可以通过从PEEPi,occl中减去Pga,exp,rise来准确估计实际的PEEPi,st。
