Objective: A 15-second end-expiratory occlusion increases cardiac preload and allows detection of preload dependence. We tested whether the reliability of this test depends upon positive end-expiratory pressure.
Design: Prospective study.
Setting: Medical ICU.
Patients: Thirty-four patients presenting with acute circulatory failure and acute respiratory distress syndrome ventilated with a tidal volume of 6.7 mL/kg (interquartile range, 6.3–7.1).
Measurements: At positive end-expiratory pressure = 5 cm H2O, we measured the changes in cardiac index induced by end-expiratory occlusion and a passive leg raising test. Preload dependence was defined by a passive leg raising–induced increase in cardiac index greater than or equal to 10%. Positive end-expiratory pressure was increased to a plateau pressure of 30 cm H2O, and end-expiratory occlusion and passive leg raising were performed again.
Main Results: At positive end-expiratory pressure = 5 cm H2O, 29% of patients were passive leg raising responders. An end-expiratory occlusion–induced increase in cardiac index greater than or equal to 5% detected a passive leg raising–induced increase in cardiac index greater than or equal to 10% with a sensitivity of 90% (95% CI, 56–100) and a specificity of 88% (95% CI, 68–97). At higher positive end-expiratory pressure (15 cm H2O [interquartile range, 13–15]), the plateau pressure – positive end-expiratory pressure difference did not change (15 mm Hg [14–17] vs 15 mm Hg [13–18] before the positive end-expiratory pressure increase). Increasing positive end-expiratory pressure significantly reduced cardiac index in passive leg raising responders (–27% [interquartile range, –6 to –56]) but not in other patients. At high positive end-expiratory pressure, passive leg raising increased cardiac index to a larger extent than at positive end-expiratory pressure = 5 cm H2O (19% [interquartile range, 15–34] vs 16% [interquartile range, 13–23], respectively). The proportion of passive leg raising responders significantly increased (34 vs 29%, respectively), meaning preload dependence had increased. At higher positive end-expiratory pressure, an end-expiratory occlusion–induced increase in cardiac index greater than or equal to 6% detected a passive leg raising–induced increase in cardiac index greater than or equal to 10% with a sensitivity of 100% (95% CI, 75–100) and a specificity of 90% (95% CI, 70–99).
Conclusions: The end-expiratory occlusion test is reliable for detecting preload dependence whatever the positive end-expiratory pressure during acute respiratory distress syndrome.
1AP-HP, Hôpitaux Universitaires Paris-Sud, Hôpital de Bicêtre, service de réanimation médicale, Le Kremlin-Bicêtre, France.
2Faculté de médecine Paris-Sud, EA4533, Université Paris-Sud, Le Kremlin-Bicêtre, France.
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Profs. Teboul and Monnet are members of the Medical Advisory Board of Pulsion Medical Systems and consulted for them. The remaining authors have disclosed that they do not have any potential conflicts of interest.
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