Oxygen Delivery and Uptake in the Adult Respiratory Distress Syndrome

This study was designed to determine whether acute alterations in oxygen delivery (O2) induced by the institution of positive end-expiratory pressure (PEEP) would affect oxygen uptake (O2) in patients with adult respiratory distress syndrome (ARDS). In 8 patients with ARDS who exhibited normal blood lactate concentrations, we evaluated the relationship between O2 and O2 during 3 consecutive periods: intermittent positive pressure ventilation (IPPV), continuous positive pressure ventilation (CPPV) with a 10 cm H2O PEEP, and finally CPPV with volume loading. Oxygen uptake was measured directly with a mass spectrometer system. Oxygen delivery was calculated as the product of cardiac output (thermodilution) and arterial blood oxygen content (Lex-O2 Con analyzer). By comparison with the IPPV period, application of PEEP led to a decrease of O2 which returned to baseline values when volume loading was added to PEEP. In none of the patients did O2 parallel the changes of O2. They demonstrated, therefore, a proper...