Airway pressure release ventilation and biphasic positive airway pressure: a systematic review of definitional criteria.
OBJECTIVE
The objective of this study was to identify the definitional criteria for the pressure-limited and time-cycled modes: airway pressure release ventilation (APRV) and biphasic positive airway pressure (BIPAP) available in the published literature.


METHODS
Systematic review.


METHODS
Medline, PubMed, Cochrane, and CINAHL databases (1982-2006) were searched using the following terms: APRV, BIPAP, Bilevel and lung protective strategy, individually and in combination. Two independent reviewers determined the paper eligibility and abstracted data from 50 studies and 18 discussion articles.


RESULTS
Of the 50 studies, 39 (78%) described APRV, and 11 (22%) described BIPAP. Various study designs, populations, or outcome measures were investigated. Compared to BIPAP, APRV was described more frequently as extreme inverse inspiratory:expiratory ratio [18/39 (46%) vs. 0/11 (0%), P = 0.004] and used rarely as a noninverse ratio [2/39 (5%) vs. 3/11 (27%), P = 0.06]. One (9%) BIPAP and eight (21%) APRV studies used mild inverse ratio (>1:1 to < or =2:1) (P = 0.7), plus there was increased use of 1:1 ratio [7 (64%) vs. 12 (31%), P = 0.08] with BIPAP. In adult studies, the mean reported set inspiratory pressure (PHigh) was 6 cm H2O greater with APRV when compared to reports of BIPAP (P = 0.3). For both modes, the mean reported positive end expiratory pressure (PLow) was 5.5 cm H2O. Thematic review identified inconsistency of mode descriptions.


CONCLUSIONS
Ambiguity exists in the criteria that distinguish APRV and BIPAP. Commercial ventilator branding may further add to confusion. Generic naming of modes and consistent definitional parameters may improve consistency of patient response for a given mode and assist with clinical implementation.
Rose
Louise
L
Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, 155 College Street, Room 276, Toronto, ON M5T 1P8, Canada. louise.rose@utoronto.ca
Hawkins
Martyn
M
D045422:Continuous Positive Airway Pressure / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007385:Intermittent Positive-Pressure Ventilation / Q000295:instrumentation / Q000379:methods*; D017410:Practice Guidelines as Topic; D011659:Pulmonary Gas Exchange