PERSISTENCE OF SUPPLY DEPENDENCY OF OXYGEN-UPTAKE AT HIGH-LEVELS OF DELIVERY IN ADULT RESPIRATORY-DISTRESS SYNDROME

Objective: To identify any plateau in oxygen consumption (Vo2) when oxygen delivery (Do2) is increased in patients with the adult respiratory distress syndrome (ARDS). Design: Clinical prospective study; multiple regression analysis was done to assess the relationship between Vo2 and Do2 for pooled data and for each individual patient. Setting: University hospital ICU. Patients: Twenty consecutive patients aged 18 to 78 yrs (mean 43.5) in whom ARDS was present during their ICU stay. Interventions: Multiple measurements were obtained in individual patients (mean number of measurements 40, range 20 to 83) and mathematical models were fitted to both pooled and individual patient data. Do2 ranged from 212 to 1550 mL/min.m2 with a maximum of 758 to 1550 mL/min.m2 (mean 1136). Because of the large variations between patients, it was not justifiable to describe a relationship for the pooled data and each case was analyzed individually. Measurements and Main Results: We found the optimal regression model to be linear in 13 patients, cubic in four, and either cubic or linear in one. Two patients demonstrated no significant relationship. The relationship for the group was determined from each patient's data and was best described by linear regression. Conclusions: In no patient was there evidence of a plateau, despite high levels of Do2 being achieved in all patients.