Bshouty Z, Ali J, Younes M
Respiratory Investigation Unit, University of Manitoba, Winnipeg, Canada.
J Appl Physiol (1985). 1988 May;64(5):1900-7. doi: 10.1152/jappl.1988.64.5.1900.
The effects of raising tidal volume and positive end-expiratory pressure (PEEP) on rate of edema formation were studied in in situ canine left upper lobe preparations. Edema was induced by increasing blood flow to the left upper lobe (4-8 times normal). In the same animal, at equivalent flows and microvascular hydrostatic pressures, rate of edema formation observed with larger tidal volumes was significantly higher than that observed with smaller tidal volumes (0.73 +/- 0.29 vs. 0.58 +/- 0.30, P less than 0.001). Edema was also induced under static conditions (i.e., flow = 0) over a wide range of vascular pressures. Rate of edema formation was plotted against pressure and the best-fit linear regression was obtained. The slopes (g.min-1.mmHg-1.100 g-1) of the regression lines were significantly higher with larger tidal volumes compared with smaller tidal volumes [0.106 +/- 0.010 (SE) vs. 0.081 +/- 0.009, P less than 0.01]. The pressure intercepts were not different (16.1 +/- 1.6 vs. 15.7 +/- 1.8). When mean airway pressures were increased to levels equivalent to those obtained with larger tidal volumes, but by raising end-expiratory pressures, rate of edema formation dropped to levels below base line. We conclude that increasing the amplitude of cyclic changes in lung volume increases edema formation through mechanisms that are independent of changes in operating (i.e., mean) lung volume.
在犬左上叶原位标本中研究了增加潮气量和呼气末正压（PEEP）对水肿形成速率的影响。通过增加左上叶血流量（为正常的4 - 8倍）诱导水肿形成。在同一动物中，在相同流量和微血管静水压条件下，较大潮气量时观察到的水肿形成速率显著高于较小潮气量时观察到的速率（0.73±0.29对0.58±0.30，P＜0.001）。还在广泛的血管压力范围内在静态条件下（即流量 = 0）诱导水肿。将水肿形成速率与压力作图并获得最佳拟合线性回归。与较小潮气量相比，较大潮气量时回归线的斜率（g·min⁻¹·mmHg⁻¹·100g⁻¹）显著更高[0.106±0.010（标准误）对0.081±0.009，P＜0.01]。压力截距无差异（16.1±1.6对15.7±1.8）。当平均气道压力升高到与较大潮气量时相当的水平，但通过提高呼气末压力来实现时，水肿形成速率降至基线以下水平。我们得出结论，增加肺容积的周期性变化幅度通过独立于工作（即平均）肺容积变化的机制增加水肿形成。
