Intravascular and Extravascular Pulmonary Fluid Volumes II. Response to Rapid Increases in Left Atrial Pressure and the Theoretical Implications for Pulmonary Radiographic and Radionuclide Imaging

摘要

Slutsky RA, Higgins CB. Intravascular and extravascular pulmonary fluid volumes II. Response to rapid increases in left atrial pressure and the theoretical implications for pulmonary radiographic and radionuclide imaging.The response of intravascular (pulmonary blood volume, PBV) and extravascular (extravascular lung water, EVLW) pulmonary fluid volume was examined using double indicator techniques (thermal-green dye) in 15 open-chest anesthetized dogs during the production of rapid left atrial (LA) hypertension by a LA balloon. In five dogs, the LA pressure was quickly increased from 1.0 plusmn; 1.1 mm Hg to 10.6 plusmn; 2.4 mm Hg (P .01), associated with an increase in PBV (164 plusmn; 76 ml to 223 plusmn; 128 ml, P .01) and an insignificant increase in EVLW (168 plusmn; 84 ml to 181 plusmn; 89 ml, P = not significant). In five dogs, the LA pressure was quickly increased from 1 plusmn; 1 mm Hg to 17.3 plusmn; 2.1 mm Hg (P .01), with a marked increase in PBV (174.3 plusmn; 81.1 ml to 262 plusmn; 127 ml, P .05) and a small change in EVLW (178 plusmn; 101 to 204 plusmn; 74 ml, P = not significant). In five dogs, LA pressure was increased from 1.0 plusmn; 0.2 mm Hg to 32.2 plusmn; 2.1 mm Hg (P .001). In these dogs, PBV rose from 206 plusmn; 99 ml to 342.8 plusmn; 12.1 ml (P .005, +66percnt; over control), while the EVLW also rose significantly (230 plusmn; 72 ml to 270 plusmn; 69, P .05) though slightly. With large rapid pressure rises, PBV rose in proportionately greater increments (delta;LA pressure 9.6 plusmn; 1.4 mm Hg, delta;PBV 59 plusmn; 8 ml; delta;LA pressure 16.4 plusmn; 1.7 mm Hg,delta;PBV 87.7 plusmn; 14.6; and delta;LA pressures of 31.3 plusmn; 2.1 mm Hg, delta;PBV of 136.8 plusmn; 31.2 ml). This study suggests that acute changes in LA pressure cause immediate increases in PBV and would presumably produce radiographically detectable pulmonary venous congestion. On the other hand, elevation in LA pressure even to levels above 30 mm Hg causes only a small immediate increase in EVLW. Because fluid transudes slowly into the extravascular space, prolonged elevation in LA pressure must occur before radioisotopes that measure EVLW could identify congestion. This study provides the physiologic basis for the proposed acute phase lag between pulmonary capillary wedge pressure and radiographic signs of pulmonary edema in acute cardiac disease states.