The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts


Steven Zhou, Robert L. Chatburn; Respiratory Institute, Cleveland Clinic, Cleveland, OH

BACKGROUND Airway Pressure Release Ventilation (APRV) is a mode of mechanical ventilation classified as pressure controlled intermittent mandatory ventilation with inverse I:E ratio. This mode allows for unrestricted spontaneous breaths and is used to treat Acute Respiratory Disease Syndrome (ARDS). Prolonged time in the high pressure (P-high) phase with short time at low pressure (P-low) allows for greater mean airway pressures, potentially resulting in greater alveolar recruitment and oxygenation. Alternating periods of high and low pressure (ie, creating mandatory breaths) helps eliminate carbon dioxide. It has been postulated that P-low = 0 cm H20 is optimal because setting P-low > 0 cm H20 would decrease peak expiratory flow and instigate an expiratory delay (Crit Care Med 2005;33(3): S228 –S240). The purpose of this study was to test these assumptions. Our hypotheses were that peak expiratory flow would be unchanged and that no delay would exist when comparing P-low settings. METHODS A lung simulator (ASL 5000, Ingmar Medical, Inc) modeled an adult ARDS patient. Simulator settings: compliance = 0.035 L/cm H20, resistance = 10 cm H20/L/sec, chest wall passive. Outcome variables were the change in peak expiratory flow (ΔPEF) and the change in peak flow delay (ΔPFD) calculated as value at P-low = 15 cm H2O minus value at P-low = 0. Data were obtained from two ventilators: Avea (CareFusion) and Evita XL (Dräger). Ventilator settings: T-high = 0.4 sec, T-low = 0.6 sec, T insp rise = 0%, ΔP of 25 cm H20. Mean values from 3 breaths were compared with t-tests with P < 0.05 indicating significance. RESULTS The peak expiratory flow for P-low = 0 cm H20 was significantly less than that for P-low = 15 cm H20 (Table) for both ventilators. There were no differences in peak flow delay. CONCLUSIONS Data from this study on 2 ventilators refute the assumption that during Airway Pressure Release Ventilation, P-low = 0 cm H20 increases PEF. Sponsored Research - None