Oxygen Delivery and Consumption and Ventricular Preload Are Greater in Survivors than in Nonsurvivors of the Adult Respiratory Distress Syndrome

Abstract

In patients with adult respiratory distress syndrome (ARDS), oxygen consumption (.ovrhdot.VO2) is pathologically dependent on oxygen delivery (DO2). Because of alterations in ventricular function, DO2 may be inadequate to satisfy oxygen demand and may contribute to multiple-system organ failure (MSOF). To determine whether there are differences in DO2, .ovrhdot.VO2 ventricular function, and MSOF, between survivors and nonsurvivors of ARDS, we studied 29 patients without cardiac disease early in the course of ARDS (hypoxemia, diffuse bilateral pulmonary infiltrate, and pulmonary artery occlusion pressure less than 18 mm Hg). Simultaneous hemodynamic, radionuclide cineangiographic, and oxygen transport measurements were made within 24 h of onset of ARDS. Thirteen survivors had greater DO2 and .ovrhdot.VO2 than did 16 nonsurvivors (p = 0.004 and 0.001, respectively). MSOF developed in no survivors and in 63% of nonsurvivors. In four survivors and in six nonsurvivors in whom DO2 was changed acutely, .ovrhdot.VO2 was dependent on DO2 (p = 0.014). Survivors had greater stroke volume index and right and left ventricular end-diastolic volume indices than did nonsurvivors despite similar right atrial and pulmonary artery occlusion pressures. There were no differences between survivors and nonsurvivors in biventricular ejection fractions. We conclude that survivors of ARDS have greater DO2 and .ovrhdot.VO2 than do nonsurvivors. Survival may be explained by the strong inverse relation between DO2 and development of MSOF. The survivors greater .ovrhdot.VO2 is related to the dependence of .ovrhdot.VO2 on DO2. The greater DO2 in survivors is due to ejection of a greater stroke volume index from greater end-diastolic volumes. This difference in end-diastolic volume may in turn be due to increased ventricular compliance as indicated by a lower ventricular diastolic pressure volume ratio.