Oxygen delivery-dependent oxygen consumption in acute respiratory failure
Lorente, J.A.; Renes, E.; Gómez-Aguinaga, M.A.; Landín, L.; de la Morena, J.; Liste, D.
Critical Care Medicine 19(6): 770-775
ISSN/ISBN: 0090-3493 PMID: 2055053 DOI: 10.1097/00003246-199106000-00007
Objective: To investigate whether oxygen consumption (.ovrhdot.VO2 is dependent on oxygen delivery (.ovrhdot.DO2) in adult respiratory distress syndrome (ARDS) and non-ARDS acute respiratory failure. Design: Intervention study of a consecutive sample of patients admitted to the ICU with the diagnosis of acute respiratory failure. Setting: Tertiary care center. Patients: Thirteen consecutive patients with a diagnosis of ARDS and 11 with a diagnosis of respiratory failure not due to ARDS. Patients were monitored with an oximetric pulmonary artery catheter and mechanically ventilated. Interventions: .ovrhdot.DO2 was decreased by the application of positive end-expiratory pressure (PEEP) (20 cm H2O), and subsequently increased by an iv infusion of dobutamine (10 .mu.g/kg .cntdot. min). Results: After the application of PEEP, .ovrhdot.DO2 decreased significantly in both groups. However, .ovrhdot.VO2 decreased significantly (p < .01) only in the ARDS group. When dobutamine was infused, .ovrhdot.DO2 increased significantly (p < .01) in both groups, but .ovrhdot.VO2 increased only in ARDS patients. .ovrhdot.DO2 correlated significantly with .ovrhdot.VO2 both in ARDS (r2 = .81, p < .01) and in non-ARDS (r2 = .38, p < .05) patients. The correlation coefficient was significantly higher for ARDS than for non-ARDS patients. Comparing the slopes of the regression lines, a stronger dependency of .ovrhdot.VO2 on .ovrhdot.DO2 was found in ARDS than in non-ARDS respiratory failure (p < .001). The oxygen extraction ratio correlated with .ovrhdot.DO2 in non-ARDS patients (r2 = .49, p < .05), but not in ARDS patients. Conclusions: .ovrhdot.VO2 is dependent on .ovrhdot.DO2 over a wide range of .ovrhdot.DO2 values in acute respiratory failure. This dependency phenomenon is much stronger in ARDS than in respiratory failure due to other causes. Due to the abnormal dependency of .ovrhdot.VO2 on .ovrhdot.DO2, changes in the oxygenation status may not be reflected by changes in mixed venous oxygen saturation in ARDS.