Maarek J M, Hakim T S, Chang H K
Department of Biomedical Engineering, University of Southern California, Los Angeles 90089-1451.
J Appl Physiol (1985). 1990 Feb;68(2):761-9. doi: 10.1152/jappl.1990.68.2.761.
In isolated canine lung lobes perfused with a pulsatile pump, arterial occlusions were performed and the postocclusion arterial pressure profiles were analyzed to estimate the pulmonary capillary pressure. A solenoid valve interposed between the pump and the lobar artery was used to perform arterial occlusions at several instants equally distributed within a pressure cycle. Double occlusions were also accomplished by simultaneously activating the solenoid valve and clamping the venous outflow of the lung lobe. To analyze an arterial occlusion pressure profile, we computed the best monoexponential fit of the pressure decay over a short period of time after the occlusion maneuvers. Two estimates of the capillary pressure were derived from this analysis: 1) the extrapolation of the exponential fit to the instant of occlusion, and 2) the point at which the recorded pressure decay curve merges with the exponential fit. The pressures thus determined were compared with the double occlusion pressure that provided an independent estimate of the pulmonary capillary pressure. Our results show that, under a wide range of conditions, the estimates of the capillary pressure obtained from the arterial occlusion data are nearly equal to the double occlusion pressures. Additionally, we estimated the capillary pressure variations within a pressure cycle by examining the occlusion pressures sampled at different instants of the cycle. The pulsatility of the pulmonary microvascular pressure varied with the pump frequency as well as the state of arterial and venous vasoaction. These variations are consistent with the representation of the lung vasculature as a low-pass filter.
在使用搏动泵灌注的离体犬肺叶中，进行动脉闭塞，并分析闭塞后动脉压力曲线以估计肺毛细血管压力。在泵和肺叶动脉之间插入一个电磁阀，用于在压力周期内等间隔的几个时刻进行动脉闭塞。通过同时激活电磁阀和夹住肺叶的静脉流出道也可实现双重闭塞。为了分析动脉闭塞压力曲线，我们在闭塞操作后的短时间内计算了压力衰减的最佳单指数拟合。从该分析中得出了两种毛细血管压力估计值：1）指数拟合外推到闭塞瞬间的值，以及2）记录的压力衰减曲线与指数拟合合并的点。将由此确定的压力与提供肺毛细血管压力独立估计值的双重闭塞压力进行比较。我们的结果表明，在广泛的条件下，从动脉闭塞数据获得的毛细血管压力估计值几乎等于双重闭塞压力。此外，我们通过检查在周期不同时刻采样的闭塞压力来估计压力周期内的毛细血管压力变化。肺微血管压力的搏动性随泵频率以及动脉和静脉血管作用状态而变化。这些变化与将肺血管系统表示为低通滤波器是一致的。
