Different oxygen transport patterns in patients with adult respiratory distress syndrome treated with positive end-expiratory pressure

Abstract

To test the hypothesis that different oxygen transport patterns reported in adult respiratory distress syndrome (ARDS) could be due to the presence of sepsis, we prospectively studied 28 mechanically ventilated patients with ARDS who received positive end-expiratory pressure (PEEP) at 0, 5, 10, and 15 cm H 2O. Nonseptic patients showed a strong correlation between oxygen delivery index (DO 2I) and mixed venous oxygen saturation (S vO 2 ) ( r = .77, P < .001) and DO 2I and oxygen extraction ratio (O 2ER) ( r = −.87, P < .001), and a correlation between DO 2I and oxygen consumption index (VO 2I) best described by third-degree polynomial fit ( r = .86) which allowed the description of a critical DO 2 point of 293 mL/min/m 2. Septic patients showed no consistent relationship between DO 2I and S vO 2 ( r = .21, P = NS), and DO 2I and O 2ER ( r = −.21, P = NS), but DO 2I and VO 2I correlated linearly ( r = .72, P < .001) in what has been described as pathologic dependence of VO 2 on DO 2. We suggest that sepsis seems to be the determinant of this abnormal relationship between supply and utilization of oxygen in our ARDS patients treated with PEEP.