• Ehab G Daoud and Robert L Chatburn.
• Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44106, USA.
• Respir Investig. 2014 Jul 1;52(4):236-41.

BackgroundNo objective data directly comparing the 2 modes are available. Based on a simple mathematical model, APRV and BIPAP can presumably be set to achieve the same mean airway pressure (mPaw), end expiratory pressure, and tidal volume (V(T)). Herein, we tested this hypothesis when using a real ventilator and clinically relevant settings based on expiratory time constants.MethodsA spontaneously breathing acute respiratory distress syndrome patient was modeled with a lung simulator. Mode settings: P high and the number of releases were the same in both modes; T low=1 time constant in APRV (expected auto-positive end-expiratory pressure [PEEP], ≈9 cmH(2)O) and 5 time constants in BIPAP; P low, 0 cmH(2)O in APRV and 9 cmH(2)O in BIPAP (equal to the expected auto-PEEP in APRV). The mean mandatory release volumes, minute ventilation [V(E)], mPaw, and total PEEP were compared with t-tests using a P value of 0.05 to reject the null hypothesis.ResultsAPRV yielded significantly higher mPaw than did BIPAP. Minute ventilation was significantly higher in BIPAP. The total PEEP was significantly higher in APRV; the total PEEP was significantly higher than expected.ConclusionWe found that neither mode was superior to the other, and that a real ventilator does not behave like a mathematical model. Extreme prolongation of T high generated a higher mPaw at the expense of V(E), and vice versa. The lower V(T) with APRV was due to the higher total PEEP, which was higher than expected. Setting the T low according to the respiratory system time constant for either mode resulted in an unpredictable total PEEP.Copyright © 2014 The Japanese Respiratory Society. Published by Elsevier B.V. All rights reserved.

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