Use of volume loading to obtain preferred levels of PEEP

Hemodynamic and oxygen transport measurements were made with successive increments of positive end-expiratory pressure (PEEP) in 14 episodes of ARDS in 11 patients who had normal or slightly increased blood volumes. "Preferred" or optimal PEEP was defined as the PEEP value associated with the greatest VO2 that did not compromise pulmonary function as determined by shunting (Qs/Qt). The preferred PEEP averaged 10.7 +/- 2.7 (SD) cm H2O in the patients who had appreciable reduction in cardiac index (CI) by the time this level of PEEP was reached. In 6 patients, the CI fell approximately 15%; then albumin, 25 g, was given. This restored CI, improved oxygen transport, and permitted us to give additional 10-15 cm H2O of PEEP, i.e., until 20--25 cm H2O was reached; this was achieved without hemodynamic impairment. The final preferred PEEP in these patients averaged 14.1 +/- 3.6 (SD) cm H2O. The authors conclude that the titration of PEEP as well as fluid therapy may be used to maximize VO2 in patients with early shock lung.