• Rudolf Hering, Doris Peters, Jörg Zinserling, Hermann Wrigge, Tilman von Spiegel, and Christian Putensen.
• Department of Anesthesiology and Intensive Care Medicine, University of Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany. hering@uni-bonn.de
• Intensive Care Med. 2002 Oct 1;28(10):1426-33.

ObjectiveControlled mechanical ventilation can impair systemic and renal blood flow and function, which may be aggravated by respiratory acidosis. We hypothesized that partial ventilatory support using airway pressure release ventilation (APRV) with spontaneous breathing provides better cardiopulmonary and renal function than full ventilatory support using APRV without spontaneous breathing.DesignProspective randomized study.SettingIntensive care unit of a university hospital.PatientsTwelve patients with acute lung injury (ALI).InterventionsAirway pressure release ventilation with and without spontaneous breathing, maintaining either the same minute ventilation (V(E)) or the same airway pressure (Paw) limits.MeasurementsSystemic hemodynamics were estimated by double-indicator dilution, effective renal blood flow (ERBF) by para-aminohippurate, and glomerular filtration rate (GFR) by inulin clearance.ResultsCompared to APRV with spontaneous breathing, cardiac index (CI) was decreased when the upper Paw limit was increased to provide the same V(E) (4.26+/-1.21 l min(-1) m(-2)vs 3.72+/-0.99 l min(-1) m(-2); p<0.05) while CI was increased when Paw limits were held constant (4.91+/-1.41 l min(-1) m(-2); p<0.05). Effective renal blood flow and GFR were higher during APRV with spontaneous breathing (858+/-388 ml min(-1) m(-2) and 94+/-47 ml min(-1) m(-2)) than during APRV without spontaneous breathing and the same V(E) (714+/-236 ml min(-1) m(-2)and 82+/-35 ml min(-1) m(-2)) or the same Paw (675+/-287 ml min(-1) m(-2) and 80+/-41 ml min(-1) m(-2); p<0.05). Urine volume did not change.ConclusionsSpontaneous breathing during APRV was associated with better renal perfusion and function than APRV without spontaneous breathing applying either the same V(E) or the same Paw limits. Maintaining spontaneous breathing during ventilatory support may, therefore, be advantageous in preventing deterioration of renal function in patients with ALI.

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