Obermiller T, Lakshminarayan S, Willoughby S, Mendenhall J, Butler J
Department of Pulmonary and Critical Care Medicine, University of Washington, Seattle.
J Appl Physiol (1985). 1992 Jul;73(1):195-9. doi: 10.1152/jappl.1992.73.1.195.
We have reported that left atrial blood refluxes through the pulmonary veins to gas-exchanging tissue after pulmonary artery ligation. This reverse pulmonary venous flow (Qrpv) was observed only when lung volume was changed by ventilation. This was believed to drive Qrpv by alternately distending and compressing the alveolar and extra-alveolar vessels. Because lung and pulmonary vascular compliances change with lung volume, we studied the effect of positive end-expiratory pressure (PEEP) on the magnitude of Qrpv during constant-volume ventilation. In prone anesthetized goats (n = 8), using the right lung to maintain normal blood gases, we ligated the pulmonary and bronchial arterial inflow to the left lung and ventilated each lung separately. A solution of SF6, an inert gas, was infused into the left atrium. SF6 clearance from the left lung was determined by the Fick principle at 0, 5, 10, and 15 and again at 0 cmH2O PEEP and was used to measure Qrpv. Left atrial pressure remained nearly constant at 20 cmH2O because the increasing levels of PEEP were applied to the left lung only. Qrpv was three- to fourfold greater at 10 and 15 than at 0 cmH2O PEEP. At these higher levels of PEEP, there were greater excursions in alveolar pressure for the same ventilatory volume. We believe that larger excursions in transpulmonary pressure during tidal ventilation at higher levels of PEEP, which compressed alveolar vessels, resulted in the reflux of greater volumes of left atrial blood, through relatively noncompliant extra-alveolar veins into alveolar corner vessels, and more compliant extra-alveolar arteries.
我们曾报道，肺动脉结扎后左心房血液经肺静脉反流至气体交换组织。这种反向肺静脉血流（Qrpv）仅在通气改变肺容积时才会观察到。据信这是通过交替扩张和压缩肺泡及肺泡外血管来驱动Qrpv的。由于肺和肺血管顺应性随肺容积变化，我们研究了在定容通气期间呼气末正压（PEEP）对Qrpv大小的影响。在俯卧位麻醉山羊（n = 8）中，利用右肺维持正常血气，我们结扎了左肺的肺动脉和支气管动脉血流，并分别对每侧肺进行通气。将一种惰性气体六氟化硫（SF6）溶液注入左心房。根据菲克原理，在0、5、10和15分钟时以及再次在0 cmH2O PEEP水平下测定左肺中SF6的清除率，并用其来测量Qrpv。左心房压力在20 cmH2O时几乎保持恒定，因为仅对左肺施加了逐渐升高的PEEP水平。在10和15 cmH2O PEEP时，Qrpv比在0 cmH2O PEEP时大三至四倍。在这些较高的PEEP水平下，对于相同的通气量，肺泡压力有更大的波动。我们认为，在较高PEEP水平下进行潮式通气时，跨肺压的更大波动压缩了肺泡血管，导致更多的左心房血液通过相对不顺应的肺泡外静脉反流至肺泡角血管以及更顺应的肺泡外动脉。
