Putensen C, Räsänen J, López F A
Department of Anesthesiology, University of South Florida, College of Medicine, Tampa.
Am J Respir Crit Care Med. 1994 Jul;150(1):101-8. doi: 10.1164/ajrccm.150.1.8025733.
Biphasic positive airway pressure (BIPAP) allows unrestricted spontaneous breathing throughout mechanical ventilation. Effects of spontaneous breathing during BIPAP on pulmonary gas exchange were studied on a randomized basis in 12 dogs with oleic acid-induced lung injury using the multiple inert gas elimination technique. Spontaneous breathing during BIPAP, accounting for 10% of minute ventilation (VE), increased PaO2 from 61 +/- 2 to 78 +/- 3 mm Hg (mean +/- SE) (p < 0.01), cardiac output from 4.2 +/- 0.3 to 4.6 +/- 0.3 L/min (p < 0.05), and oxygen delivery from 537 +/- 51 to 716 +/- 58 ml/kg/min (p < 0.05), whereas oxygen consumption and total VE remained unchanged. Improved pulmonary gas exchange caused by better ventilation/perfusion (VA/Q) matching was indicated by a 17 +/- 3% decrease (p < 0.01) in blood flow to shunt units (VA/Q < 0.005), a 15 +/- 3% increase (p < 0.05) in perfusion of normal VA/Q units (0.1 < VA/Q < 10), and a 6 +/- 3% reduction in ventilation of dead space (VA/Q > 100) areas (p < 0.05). Spontaneous breaths superimposed on mechanical ventilation may convert shunt VA/Q units to normal by increased ventilation of poorly or nonventilated units and/or increase blood flow to previously minimal or nonperfused areas.
双水平气道正压通气（BIPAP）允许在整个机械通气过程中进行不受限制的自主呼吸。使用多惰性气体消除技术，在12只油酸诱导的肺损伤犬中，随机研究了BIPAP期间自主呼吸对肺气体交换的影响。BIPAP期间的自主呼吸占分钟通气量（VE）的10%，使动脉血氧分压（PaO2）从61±2毫米汞柱升至78±3毫米汞柱（平均值±标准误）（p<0.01），心输出量从4.2±0.3升/分钟增至4.6±0.3升/分钟（p<0.05），氧输送量从537±51毫升/千克/分钟增至716±58毫升/千克/分钟（p<0.05），而氧耗量和总VE保持不变。更好的通气/灌注（VA/Q）匹配导致肺气体交换改善，表现为分流单位（VA/Q<0.005）的血流减少17±3%（p<0.01），正常VA/Q单位（0.1<VA/Q<10）的灌注增加15±3%（p<0.05），死腔（VA/Q>100）区域的通气减少6±3%（p<0.05）。叠加在机械通气上的自主呼吸可能通过增加通气不良或无通气单位的通气量和/或增加流向先前灌注极少或无灌注区域的血流，将分流的VA/Q单位转变为正常单位。
