Ayappa I, Brown L V, Wang P M, Katzman N, Houtz P, Bruce E N, Lai-Fook S J
Center for Biomedical Engineering, Wenner-Gren Research Laboratory, University of Kentucky, Lexington 40506 0070, USA.
Respir Physiol. 1996 Sep;105(3):203-16. doi: 10.1016/0034-5687(96)00056-4.
We used an isolated perfused lung preparation of the rabbit to study the effect of increasing blood flow on pulmonary capillary transit time by two methods. In one method, capillary transit time was measured from fluorescent dye dilution curves from arterioles and venules of the subpleural microcirculation. Values of transit time were similar to those for the whole lung determined by dividing capillary blood volume by blood flow. Capillary transit times averaged 0.50-0.62 sec at a control blood flow of 80 ml min-1 kg-1 and decreased to 0.14-0.18 sec as blood flow increased to 6 times control. To determine whether the reduced transit time would limit O2 transport, we studied the effect of blood flow on oxygenation. Two isolated rabbit lungs were perfused in series. Blood from one lung deoxygenated by ventilation with a N2-CO2 mixture was oxygenated by the test lung ventilated with air. Ventilation was matched to blood flow. PO2 and PCO2 were measured in blood flowing into and out of the test lung. At all flows, no significant alveolar gas-to-end-capillary blood PO2 gradient (A-aDO2) was measured. The isolated perfused rabbit lung showed no transit time limitation to oxygenation for blood flows that are consistent with heavy exercise in vivo.
我们采用兔离体灌注肺标本，通过两种方法研究增加血流对肺毛细血管转运时间的影响。一种方法是根据胸膜下微循环中小动脉和小静脉的荧光染料稀释曲线来测量毛细血管转运时间。转运时间的值与通过将毛细血管血容量除以血流来确定的全肺转运时间值相似。在80 ml·min⁻¹·kg⁻¹的对照血流下，毛细血管转运时间平均为0.50 - 0.62秒，当血流增加至对照的6倍时，转运时间降至0.14 - 0.18秒。为了确定转运时间缩短是否会限制氧气运输，我们研究了血流对氧合的影响。将两只兔离体肺串联灌注。用氮气 - 二氧化碳混合气通气使一只肺的血液脱氧，然后由用空气通气的受试肺使其氧合。通气与血流相匹配。测量流入和流出受试肺的血液中的PO₂和PCO₂。在所有血流情况下，均未测得显著的肺泡气 - 终末毛细血管血PO₂梯度（A - aDO₂）。对于与体内剧烈运动相符的血流，兔离体灌注肺未显示出转运时间对氧合的限制。
