In isolated dog lobes, pulmonary artery wedge pressure does not equal alveolar or average critical pressure, but is determined by closing pressures and downstream drainage time-constants.
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Wedge pressure may not reflect alveolar or critical closing pressure; leaves open human validation of pulmonary vascular models.
We studied the relationship between the pulmonary artery wedge pressure (Pw) and pulmonary venous pressure (Ppv) at 2 alveolar pressures (PA) in 7 isolated perfused dog lobes. If PA were the critical pressure in the pulmonary circulation, one would expect Pw to equal Ppv for all Ppv greater than PA. Relative to the hilum, the average critical pressure in these lobes was 15.07 +/- 0.40 cmH2O at PA = 5 cmH2O and increased significantly to 17.23 +/- 0.82 cmH2O at PA = 7 cmH2O. Because the critical pressure in fact exceeded PA, Pw was found to be relatively constant and independent of Ppv even when Ppv exceeded PA by 5 cmH2O or more. For example, at PA = 5.13 +/- 0.04 cmH2O and Ppv = 9.64 +/- 0.28, the mean value for Pw was 13.30 +/- 0.59 cmH2O. Pw is equal neither to the average critical pressure nor to PA, but instead lies between these two values. It is determined by the spectrum of closing pressures in the pulmonary circulation, and the time-constants for drainage of beds downstream from the occluded pulmonary arterial branch.
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Jasper et al. (1986) studied this question.
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