Tanita T, Onizuka M, Staub N C
Cardiovascular Research Institute, University of California, San Francisco 94143-0130.
J Appl Physiol (1985). 1988 Jul;65(1):337-42. doi: 10.1152/jappl.1988.65.1.337.
To determine how liquid accumulation affects extra-alveolar perimicrovascular interstitial pressure, we measured filtration rate under zone 1 conditions (25 cmH2O alveolar pressure, 20 or 10 cmH2O vascular pressure) in isolated dog lung lobes in which all vessels were filled with autologous plasma. In the base-line condition, starting with normal extra-alveolar water content, filtration rate decreased by about one-half over 1 h as edema liquid slowly accumulated. We repeated each experiment after inducing edema (up to 100% lung weight gain). The absolute values and time course of filtration in the edema condition did not differ from base-line, i.e., the edema did not affect the time course of filtration. To compute the maximal initial and maximal change in extra-alveolar perimicrovascular pressure that occurred over each 1-h filtration study, we first assumed that the reflection coefficient is 0 in the Starling equation, then calculated perimicrovascular pressure and filtration coefficient from two equations with two unknowns. The mean filtration coefficient in 10 lobes is 0.063 g/(min X cmH2O X 100 g wet wt), and the initial perimicrovascular pressure is 3.9 cmH2O, rising by 4-7 cmH2O at 1 h. Finally we tested low protein perfusates and found the filtration rate was higher. We calculated an overall reflection coefficient = 0.44, a decrease in the initial perimicrovascular pressure to 1.9 cmH2O and a slightly lower increase after 1 h of edema formation, 2.2-6.6 cmH2O.
为了确定液体蓄积如何影响肺泡外微血管周围间质压力，我们在区域1条件下（肺泡压25 cmH₂O，血管压20或10 cmH₂O）测量了分离的犬肺叶的滤过率，其中所有血管都充满了自体血浆。在基线条件下，从正常的肺泡外含水量开始，随着水肿液缓慢蓄积，滤过率在1小时内下降了约一半。在诱发水肿（肺重量增加高达100%）后，我们重复了每个实验。水肿条件下滤过的绝对值和时间进程与基线无差异，即水肿不影响滤过的时间进程。为了计算在每次1小时滤过研究中发生的肺泡外微血管周围压力的最大初始值和最大变化，我们首先假设在Starling方程中反射系数为0，然后从两个含有两个未知数的方程中计算微血管周围压力和滤过系数。10个肺叶的平均滤过系数为0.063 g/(min×cmH₂O×100 g湿重)，初始微血管周围压力为3.9 cmH₂O，在1小时时升高4 - 7 cmH₂O。最后，我们测试了低蛋白灌注液，发现滤过率更高。我们计算出总体反射系数 = 0.44，初始微血管周围压力降至1.9 cmH₂O，水肿形成1小时后的升高略低，为2.2 - 6.6 cmH₂O。
