Transthoracic Bioimpedance Can Measure Extravascular Lung Water in Acute Lung Injury

Abstract

We used a porcine endotoxemic model of acute lung injury to compare extravascular lung water (EVLW) measured by right transthoracic bioimpedance to postmortem gravimetric EVLW measurements. Adult pigs were randomized into control (N= 5) or endotoxin groups [150 μg/kgEscherichia colilipopolysaccharide B for 1 hr followed by 3 hr of resuscitation for a thermodilution cardiac output less than 90% of baseline using either isotonic saline (N= 5) or isooncotic albumin (N= 5)]. Right lung resistance was measured using a novel electrode array and a highly sensitive analyzer and was used to calculate right lung resistivity. At the end of the experiment, animals in the endotoxin–albumin group had higher gravimetric EVLWs than those in the endotoxin–saline or control groups (P< 0.05). Right lung resistivity corrected for body weight significantly correlated with gravimetric EVLW (r2= 0.49; SEE = 0.96;P= 0.0038). Using multiple regression analysis, a predictive equation for EVLW based on right lung resistivity, body weight, and mean pulmonary artery pressure was generated (r2= 0.81; SEE = 0.60;P< 0.0001). These results demonstrate that right lung resistivity measurements can provide a noninvasive estimate of EVLW. In addition, crystalloid may be preferable to colloid for fluid resuscitation in noncardiogenic pulmonary edema.