Aprv

Review Article

The Journal of TRAUMA Injury, Infection, and Critical Care

Airway Pressure Release and Biphasic Intermittent Positive Airway Pressure Ventilation: Are They Ready for Prime Time?
Christopher W. Seymour, MD, Michael Frazer, BS, RRT, CPFT, Patrick M. Reilly, MD, FACS, and Barry D. Fuchs, MD, FCCP

Airway pressure release ventilation and biphasic positive airway pressureventilation are being used increasingly as alternative strategies to conventional assist control ventilation for patients with acute respiratory distress syndrome (ARDS) and acute lung injury. By permitting spontaneous breathing throughout the ventilatory cycle, these modes offer sev-

eral advantages over conventional strategies to improve the pathophysiology in these patients, including gasexchange, cardiovascular function, and reducing or eliminating the need for heavy sedation and paralysis. Whether these surrogate outcomes will translate into better patient outcomes remains to be determined. The purpose of this review is to summarize the

rationale behind the use of these ventilatory strategies in ARDS, the clinical experience with the use of these modes, and their future applicationsin trauma patients. Key Words: Acute respiratory distress syndrome, airway pressure release ventilation, mechanical ventilation.
J Trauma. 2007;62:1298 –1309.

irway pressure release ventilation (APRV) is a mode of mechanical ventilation designed to allow patients to breathe spontaneously while receiving high levels of continuous positive airway pressure (CPAP). This ventilator mode was firstproposed by Downs and Stock in 1987 after study in canines with acute lung injury as a means to augment alveolar ventilation while allowing spontaneous respiratory efforts throughout an inversed mechanical ventilatory cycle.1 Biphasic positive airway pressure ventilation (BIPAP) is similar to APRV in allowing spontaneous breathing, but there are no restrictions on the timing of the pressurerelease. Thus, in BIPAP, spontaneous breathing efforts may be present during the longer release phase. These ventilator modes have been increasingly studied in critically ill patients with acute lung injury, gaining popularity because of their ability to reduce sedation and neuromuscular blockade. Most recently, a retrospective review demonstrated that APRV was a safe alternative for traumaticallyinjured patients at high risk for acute lung injury/acute respiratory distress syndrome.2 The goal of this review is to provide a summary of the pathophysiologic basis for the use of these ventilatory modes
Submitted for publication January 22, 2006. Accepted for publication October 16, 2006. Copyright © 2007 by Lippincott Williams & Wilkins, Inc. From the Division of Traumatology and SurgicalCritical Care, Department of Surgery (P.M.R.), and the Division of Pulmonary, Allergy, and Critical Care, Department of Medicine (C.W.S., M.F., B.D.F.), Hospital of the University of Pennsylvania, Philadelphia, PA. Address for reprints: Barry D. Fuchs, M.D., F.C.C.P., Medical Intensive Care Units and Respiratory Care, Pulmonary, Allergy, and Critical Care Division, Hospital of the University ofPennsylvania, 9.066 Founders Building, 3400 Spruce St., Philadelphia, PA 19104-4283; e-mail: barry.fuchs@ uphs.upenn.edu. DOI: 10.1097/TA.0b013e31803c562f

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in ARDS, discuss the implicit advantages of spontaneous breathing with these ventilator strategies, and review the recent clinical experience with APRV and BIPAP in critically ill patients.

Acute Lung Injury and Acute Respiratory DistressSyndrome
Acute lung injury is characterized by a heterogeneous pattern of diffuse alveolar damage resulting from either a direct, indirect, or a combination of insults to the lung.3 Well described by Gattinoni and colleagues, the injured lung in acute respiratory distress syndrome (ARDS) is heterogeneous in gas and fluid distribution, with variable computed tomography findings within individual...