Pitt Ford T R, Sachs J R, Grotberg J B, Glucksberg M R
Biomedical Engineering Department, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208.
J Appl Physiol (1985). 1991 Jun;70(6):2750-6. doi: 10.1152/jappl.1991.70.6.2750.
We have developed a method to characterize fluid transport through the perialveolar interstitium using micropuncture techniques. In 10 experiments we established isolated perfused rat lung preparations. The lungs were initially isogravimetric at 10 cmH2O arterial pressure, 2 cmH2O venous pressure, and 5 cmH2O alveolar pressure. Perialveolar interstitial pressure was determined by micropuncture at alveolar junctions by use of the servo-null technique. Simultaneously a second micropipette was placed in an alveolar junction 20-40 microns away, and a bolus of albumin solution (3.5 g/100 ml) was injected. The resulting pressure transient was recorded for injection durations of 1 and 4 s in nonedematous lungs. The measurements were repeated after gross edema formation induced by elevated perfusion pressure. We model the interstitium as a homogeneous linearly poroelastic material and assume the initial pressure distribution due to the injection to be Gaussian. The pressure decay is inversely proportional to time, with time constant T, where T is a measure of the ratio of interstitial tissue stiffness to interstitial resistance to fluid flow. A linear regression was performed on the reciprocal of the pressure for the decaying portion of the transients to determine T. Comparing pressure transients in nonedematous and edematous lungs, we found that T was 4.0 +/- 1.4 and 1.4 +/- 0.6 s, respectively. We have shown that fluid transport through the pulmonary interstitium on a local level is sensitive to changes in interstitial stiffness and resistance. These results are consistent with the decreased stiffness and resistance in the perialveolar interstitium that accompany increased hydration.
我们已经开发出一种使用微穿刺技术来表征液体通过肺泡周围间质运输的方法。在10个实验中，我们建立了离体灌注大鼠肺标本。最初，肺在动脉压10 cmH₂O、静脉压2 cmH₂O和肺泡压5 cmH₂O时处于等重力状态。通过使用伺服零位技术，在肺泡连接处进行微穿刺来测定肺泡周围间质压力。同时，将第二个微量移液器放置在距离20 - 40微米的另一个肺泡连接处，并注入白蛋白溶液团（3.5 g/100 ml）。在非水肿肺中，记录注射持续时间为1秒和4秒时产生的压力瞬变。在因灌注压升高导致严重水肿形成后，重复进行测量。我们将间质建模为均匀的线性多孔弹性材料，并假设由于注射引起的初始压力分布为高斯分布。压力衰减与时间成反比，时间常数为T，其中T是间质组织刚度与间质对流体流动阻力之比的一种度量。对瞬变衰减部分的压力倒数进行线性回归以确定T。比较非水肿肺和水肿肺中的压力瞬变，我们发现T分别为4.0 +/- 1.4秒和1.4 +/- 0.6秒。我们已经表明，在局部水平上，液体通过肺间质的运输对间质刚度和阻力的变化敏感。这些结果与随着水合作用增加，肺泡周围间质刚度和阻力降低一致。
