Clinical studies of measuring extravascular lung water by the thermal dye technique in critically ill patients

Abstract

We measured extravascular lung water (EVLW) by the thermal-dye technique in a broad group of critically ill patients who had either acute cardiac or noncardiac illnesses. A portable AP supine chest roentgenogram, reviewed blindly, was used to classify patients as to the presence or absence of pulmonary edema; by clinical history we categorized patients into either a cardiac or noncardiac (ie, ARDS) group. With a normal chest roentgenogram, the mean EVLW was 5.6 +/- 1.8 ml/kg, and the pulmonary capillary wedge pressure (PCWP) was 11.3 +/- 5.3 mm Hg (mean +/- SD). In contrast, patients with pulmonary edema on a cardiac basis had a mean EVLW of 10.2 +/- 3.1 ml/kg (mean PCWP, 20.5 +/- 8.2 mm Hg), while patients with clinically defined noncardiac pulmonary edema and a normal PCWP (11.6 +/- 5.7 mm Hg) had a mean EVLW of 15.8 +/- 4.6 ml/kg, significantly higher than in the cardiac group (p less than 0.001). On a severity system of 014, the EVLW increased in parallel to the severity of the chest radiologic appearance of edema in both the cardiac (r2 = .44; p less than 0.001) and noncardiac (r2 = .59; p less than 0.001) patients. This study defined a normal range of thermal-dye EVLW in critically ill patients without radiologic evidence of pulmonary edema. We further demonstrated the increased pulmonary microvascular permeability of noncardiac pulmonary edema compared with cardiac edema by the greater EVLW at normal microvascular hydrostatic pressures in the former group.