The oxygen consumption/ delivery relationship (VO2/602) was studied in 18 sedated, paralyzed, septic adult respiratory distress syndrome patients. Different levels (0 to 15 cm H2O) of positive end-expiratory pressure (PEEP) were applied. DO2 was calculated from cardiac index (thermodilution technique) and arterial oxygen content measurements. VO2 was calculated using Fick's equation. Regression lines were obtained for each patient. The following results were obtained. First, patients with DO2 at zero end-expiratory pressure ≤ 640 mL/min/m2 showed a highly significant relationship between changes in DO2 and VO2 with PEEP (supply dependency). In all these patients PEEP decreased DO2 by reducing cardiac index without significant changes in arterial oxygen saturation. All these patients developed multiple organ system failure and died. Second, changes in DO2 and VO2 with PEEP were not correlated in patients with a DO2 on zero end-expiratory pressure ≥ 686 mL/min/m2 (nonsupply dependency). As PEEP was applied, changes in DO2 were compensated by changes in oxygen extraction ratio such as to keep VO2 constant. On average, DO2 decreased with PEEP, while oxygen extraction ratio and arterial-mixed venous oxygen difference increased as PEEP was applied. Only three of these patients developed multiple organ system failure and died (70% survivors).
Oxygen delivery-consumption relationship in septic adult respiratory distress syndrome patients: The effects of positive end-expiratory pressure
RANIERI, Vito Marco;
1992-01-01
Abstract
The oxygen consumption/ delivery relationship (VO2/602) was studied in 18 sedated, paralyzed, septic adult respiratory distress syndrome patients. Different levels (0 to 15 cm H2O) of positive end-expiratory pressure (PEEP) were applied. DO2 was calculated from cardiac index (thermodilution technique) and arterial oxygen content measurements. VO2 was calculated using Fick's equation. Regression lines were obtained for each patient. The following results were obtained. First, patients with DO2 at zero end-expiratory pressure ≤ 640 mL/min/m2 showed a highly significant relationship between changes in DO2 and VO2 with PEEP (supply dependency). In all these patients PEEP decreased DO2 by reducing cardiac index without significant changes in arterial oxygen saturation. All these patients developed multiple organ system failure and died. Second, changes in DO2 and VO2 with PEEP were not correlated in patients with a DO2 on zero end-expiratory pressure ≥ 686 mL/min/m2 (nonsupply dependency). As PEEP was applied, changes in DO2 were compensated by changes in oxygen extraction ratio such as to keep VO2 constant. On average, DO2 decreased with PEEP, while oxygen extraction ratio and arterial-mixed venous oxygen difference increased as PEEP was applied. Only three of these patients developed multiple organ system failure and died (70% survivors).
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