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A Pilot Randomized Trial Comparing Weaning From Mechanical Ventilation on Pressure Support Versus Proportional Assist Ventilation*

Bosma, Karen J. MD, FRCPC; Read, Brooke A. MHS, BSc, RRT; Bahrgard Nikoo, Mohammad J. MD, FRCPC; Jones, Philip M. MD, FRCPC, MSc; Priestap, Fran A. MSc; Lewis, James F. MD, FRCPC

doi: 10.1097/CCM.0000000000001600
Clinical Investigations

Objectives: Despite protocols incorporating spontaneous breathing trials, 31% of ICU patients experience difficult or prolonged weaning from mechanical ventilation. Nonfatiguing modes such as pressure support ventilation are recommended. Proportional assist ventilation provides assistance in proportion to patient effort, which may optimize weaning. However, it is not known how proportional assist ventilation performs relative to pressure support ventilation over a prolonged period in the complex ICU setting. The purpose of this study was to compare the physiologic and clinical performance (failure rate), safety, and feasibility of protocols using daily spontaneous breathing trial plus pressure support ventilation versus proportional assist ventilation until ventilation discontinuation.

Design: Single-center, unblinded pilot randomized controlled trial.

Setting: Medical-surgical ICU of a tertiary-care hospital.

Patients: Adult patients intubated greater than 36 hours were randomized if they met eligibility criteria for partial ventilatory support, tolerated pressure support ventilation greater than or equal to 30 minutes, and either failed or did not meet criteria for a spontaneous breathing trial.

Interventions: Patients were randomized to the pressure support ventilation or proportional assist ventilation protocol (PAV+, Puritan Bennett 840; Covidien, Boulder, CO). Both protocols used progressive decreases in level of assistance as tolerated, coupled with daily assessment for spontaneous breathing trials.

Measurements and Main Results: Of 54 patients randomized, outcome data are available for 50 patients; 27 were randomized to receive proportional assist ventilation and 23 to receive pressure support ventilation. There were no adverse events linked to the study interventions, and protocol violations were infrequent. Recruitment was slower than projected (1.3 patients per month). The median (interquartile range) time from randomization to successful extubation was 3.9 days (2.8–8.4 d) on proportional assist ventilation versus 4.9 days (2.9–26.3 d) on pressure support ventilation (p = 0.39). Time to live ICU discharge was 7.3 days (5.2–11.4 d) on proportional assist ventilation versus 12.4 days (7.5–30.8 d) on pressure support ventilation (p = 0.03).

Conclusion: This pilot study demonstrates the utility, safety, and feasibility of the weaning protocols and provides important information to guide the design of a future randomized controlled trial comparing weaning from mechanical ventilation on pressure support ventilation versus proportional assist ventilation.

Supplemental Digital Content is available in the text.

1London Health Sciences Centre, London, ON, Canada.

2Department of Medicine, The University of Western Ontario, London, ON, Canada.

*See also p. 1237.

This study was performed at London Health Sciences Centre, University Hospital, London, Canada.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website (

Supported, in part, by Critical Care Western, Department of Medicine, The University of Western Ontario; Program of Experimental Medicine (POEM), Department of Medicine, University of Western Ontario; Lawson Health Research Institute, London Health Sciences Centre, London, Canada; and Covidien, Boulder, USA.

Dr. Bosma has received honourarium for lectures and travel reimbursements from Covidien. Dr. Bosma’s institution has received grant support from Covidien for Dr. Bosma’s research studies. The remaining authors have disclosed that they do not have any potential conflicts of interest.

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