Saito O, Lamm W J, Hildebrandt J, Albert R K
Department of Medicine, University of Washington, Seattle 98195, USA.
J Appl Physiol (1985). 1995 Mar;78(3):914-20. doi: 10.1152/jappl.1995.78.3.914.
We previously reported that mean pulmonary arterial pressure (Ppa) during pulsatile flow exceeded that for steady flow when flow was greater than the normal resting value and speculated that this was due to irregularities of the flow profiles in precapillary vessels, mainly the larger arteries. From this we hypothesized that neither mean microvascular pressure nor the rate of fluid filtration would be affected by flow pulsatility. We therefore compared the effects of steady vs. pulsatile flow on the double-occlusion pressure (Pdo) and on edema formation (rate of weight gain) in zone 3 rabbit lungs. Excised left lungs (n = 19) were perfused with Tyrode solution and ventilated with an end-expiratory pressure of 2.5 cmH2O. A diaphragm pump generated pulsatile flow with a stroke volume of 1.0 ml (approximately 0.8 the normal resting value for rabbit left lung). Nonpulsatile flow was generated by raising an arterial reservoir. Flow rate was set at 100 or 400 ml/min (approximately 0.4 or 1.6 x the normal resting cardiac output, respectively). Vascular pressures (referenced to the bottom of the lung) were measured after ventilation, at end expiration, was interrupted. Pdo values were obtained in random order at 15 time points that were evenly distributed within the pulse cycle, averaged across pulses to obtain the mean capillary pressure profile, and then averaged over time. At the lower flow of 100 ml/min, mean Ppa and Pdo were slightly lower (3-4%) during pulsatile compared with nonpulsatile conditions. At the higher flow of 400 ml/min, mean Ppa was higher under pulsatile conditions (13%), whereas downstream the mean Pdo values were equal.(ABSTRACT TRUNCATED AT 250 WORDS)
我们之前报道过，当流量大于正常静息值时，搏动流期间的平均肺动脉压（Ppa）超过稳定流时的平均肺动脉压，并推测这是由于毛细血管前血管（主要是较大动脉）中血流分布不规则所致。据此我们假设，微血管平均压力和液体滤过率均不会受血流搏动性影响。因此，我们比较了稳定流与搏动流对3区兔肺双阻断压力（Pdo）和水肿形成（体重增加速率）的影响。将19只切除的左肺用台氏液灌注，呼气末压力为2.5 cmH₂O进行通气。隔膜泵产生搏出量为1.0 ml（约为兔左肺正常静息值的0.8倍）的搏动流。通过升高动脉贮液器产生非搏动流。流速设定为100或400 ml/min（分别约为正常静息心输出量的0.4或1.6倍）。在通气结束、呼气末中断后测量血管压力（以肺底部为参考）。在脉搏周期内均匀分布的15个时间点以随机顺序获取Pdo值，对各脉搏进行平均以获得平均毛细血管压力曲线，然后随时间进行平均。在100 ml/min的较低流速下，搏动流期间的平均Ppa和Pdo与非搏动流条件相比略低（3 - 4%）。在400 ml/min的较高流速下，搏动流条件下的平均Ppa较高（13%），而下游的平均Pdo值相等。（摘要截断于250字）
