Schumacker P T, Sznajder J I, Nahum A, Wood L D
J Appl Physiol (1985). 1987 Mar;62(3):1255-63. doi: 10.1152/jappl.1987.62.3.1255.
Previous work by Lehnert et al. (J. Appl. Physiol. 53:483-489, 1982) has demonstrated that adequate alveolar ventilation can be maintained during apnea in anesthetized dogs by delivering a continuous stream of inspired ventilation through cannulas aimed down the main-stem bronchi. Because an asymmetric distribution of ventilation might introduce ventilation-perfusion (VA/Q) inequality, we compared gas exchange efficiency in nine anesthetized and paralyzed dogs during constant-flow ventilation (CFV) and conventional ventilation (intermittent positive-pressure ventilation, IPPV). Gas exchange was assessed using the multiple inert gas elimination technique. During CFV at 3 l X kg-1 X min-1, lung volume, retention-excretion differences (R-E*) for low- and medium-solubility gases, and the log standard deviation of blood flow (log SD Q) increased, compared with the findings during IPPV. Reducing CFV flow rate to 1 l X kg-1 X min-1 at constant lung volume improved R-E* and log SD Q, but significant VA/Q inequality compared with that at IPPV remained and arterial PCO2 rose. Comparison of IPPV and CFV at the same mean lung volume showed a similar reversible deterioration in gas exchange efficiency during CFV. We conclude that CFV causes significant VA/Q inequality which may be due to nonuniform ventilation distribution and a redistribution of pulmonary blood flow.
莱纳特等人（《应用生理学杂志》53:483 - 489，1982年）之前的研究表明，在麻醉犬呼吸暂停期间，通过沿主支气管向下插入的插管输送持续的吸入气流，可维持足够的肺泡通气。由于通气的不对称分布可能会导致通气 - 灌注（VA/Q）失衡，我们比较了9只麻醉且瘫痪的犬在恒流通气（CFV）和传统通气（间歇正压通气，IPPV）过程中的气体交换效率。使用多惰性气体消除技术评估气体交换。与IPPV期间的结果相比，在3 l·kg⁻¹·min⁻¹的CFV过程中，肺容积、低溶解度和中等溶解度气体的潴留 - 排泄差异（R - E*）以及血流的对数标准差（log SD Q）增加。在恒定肺容积下将CFV流速降至1 l·kg⁻¹·min⁻¹可改善R - E*和log SD Q，但与IPPV相比，仍存在显著的VA/Q失衡，且动脉PCO₂升高。在相同平均肺容积下比较IPPV和CFV，结果显示CFV期间气体交换效率出现类似的可逆性恶化。我们得出结论，CFV会导致显著的VA/Q失衡，这可能是由于通气分布不均匀和肺血流重新分布所致。
