Regulation of tissue oxygen extraction is disturbed in adult respiratory distress syndrome

Abstract

To test the hypothesis that regulation of tissue oxygen (O2) extraction is disturbed in adult respiratory distress syndrome (ARDS), the relationship between O2 availability and O2 extraction ratio (O2ER) was studied in 36 patients with pulmonary edema who met the criteria for either ARDS (n = 21) or acute congestive heart failure (CHF) (n = 15). We found that in response to changes in the levels of O2 availability there was a significantly (p = 0.01) greater negative correlation of change in O2ER for the CHF (r = -0.67) than for the ARDS group (r = -0.41). Whereas patients with CHF eventually died of pump failure and low O2 delivery, the ARDS group developed multiorgan failure, especially renal failure, despite significantly higher ratios of O2 availability to O2 consumption. These findings suggest that patients with ARDS have lost their ability to regulate their tissue O2 extraction to compensate for changes in the availability of O2 in order to meet demand. Pulmonary capillary endothelial injury, through its role on whole-body metabolism, may be responsible for this observation.