Indirect estimate of perimicrovascular pressure rise in edema in isolated zone 1 lung.
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.
Tanita
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Cardiovascular Research Institute, University of California, San Francisco 94143-0130.
Onizuka
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M
Staub
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D000465:Algorithms; D000818:Animals; D004285:Dogs; D005110:Extracellular Space / Q000032:analysis*; D005374:Filtration; D008833:Microcirculation; D009929:Organ Size; D011312:Pressure; D011652:Pulmonary Circulation; D011654:Pulmonary Edema / Q000503:physiopathology*; D013997:Time Factors