Meta Analysis Effect of prone positioning during mechanical ventilation on mortality among patients with acute respiratory distress syndrome: a systematic review and meta-analysis
This review may be edited
Summary
Posted By:	Pip Heighes
E-Mail:	pheighes@med.usyd.edu.au
Posted Date:	19/11/14
Title:	Effect of prone positioning during mechanical ventilation on mortality among patients with acute respiratory distress syndrome: a systematic review and meta-analysis
Authors:	Sud S, Friedrich J, Adhikari N, Taccone P, Mancebo J, Polli F, Latini R, Pesenti A, Curley M, Fernandez R, Chan M, Beuret P, Voggenreiter G, Sud M, Tognoni G, Gattitoni L & Guerin C.
Reference:	CMAJ 2014 July; 186(10) E381 - 390. DOI 10.1503/cmaj.140081
Link:	Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract:	Background: Mechanical ventilation in the prone position is used to improve oxygenation and to mitigate the harmful effects of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). We sought to determine the effect of prone positioning on mortality among patients with ARDS receiving protective lung ventilation. Methods: We searched electronic databases and conference proceedings to identify relevant randomized controlled trials (RCTs) published through August 2013. We included RCTs that compared prone and supine positioning during mechanical ventilation in patients with ARDS. We assessed risk of bias and obtained data on all-cause mortality (determined at hospital discharge or, if unavailable, after longest follow-up period). We used random-effects models for the pooled analyses. Results: We identified 11 RCTs (n = 2341) that met our inclusion criteria. In the 6 trials (n = 1016) that used a protective ventilation strategy with reduced tidal volumes, prone positioning significantly reduced mortality (risk ratio 0.74, 95% confidence interval 0.59–0.95; I2 = 29%) compared with supine positioning. The mortality benefit remained in several sensitivity analyses. The overall quality of evidence was high. The risk of bias was low in all of the trials except one, which was small. Statistical heterogeneity was low (I2 < 50%) for most of the clinical and physiologic outcomes. Interpretation: Our analysis of high-quality evidence showed that use of the prone position during mechanical ventilation improved survival among patients with ARDS who received protective lung ventilation.
Are the Results Valid?
1. Did the overview address a focused clinical question?
	Yes, the authors clearly identify the population of interest as patients with ARDS receiving protective lung ventilation with an intervention of prone positioning and a comparison of supine positioning and their intention to investigate any effect on the outcome of mortality.
2. Were the criteria used to select articles for inclusion appropriate?
	Yes, the authors included RCTs (and quasi-randomised trials) in adults and children with ARDS supported by mechanical ventilation where prone positioning was utilised and compared to supine positioning and outcomes of interest (primary - mortality or secondary - changes in oxygenation or adverse events) were reported.
3. Is it unlikely that important, relevant studies were missed?
	It is unlikely important relevant studies were missed. The authors utilised a thorough search strategy updated from their previously published systematic review (Intensive Care Med. 2010 Apr;36(4):585-99. doi: 10.1007/s00134-009-1748-1. Epub 2010 Feb 4). They searched appropriate databases including MEDLINE, Embase and CENTRAL; hand searched bibliographies and conference proceedings; and searched Clinical Trials registry and Current Controlled Trials database. Language restrictions were not used.
4. Was the validity of the included studies appraised?
	The methodological quality of each trial was assessed with an evaluation of randomisation methods and allocation concealment, blinding methods and completeness of follow up after randomisation. A modified version of the Cochrane risk of bias instrument was used to assess risk of bias. The quality of assessment of mortality (primary outcome) was determined using the GRADE approach.
5. Were assessments of studies reproducible?
	Study methods were assessed independentaly by the authors with disagreements resolved through consensus. It is not clear if the methodologic quality was assessed independently. Details of the risk of bias assessment are however clearly reported in the paper.
6. Were the results similar from study to study?
	I-square measure for the primary analysis, and all other analyses of mortality, was 'low' based on a priori specified thresholds. I-square less than 50% is an appropriate threshold to define 'low' heterogeneity.
What are the Results?
1. What are the overall results of the overview?
	The primary analysis was based on clinical trials using lung-protective ventilation: Proning significantly reduced mortality (RR 0.74, 95% CI 0.59 to 0.95, I-square = 29%).
2. How precise were the results?
	The 95% Confidence interval around the results for the primary outcome of mortality was precise (see above).
Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care
	Yes, the implementation of prone positioning should be achievable in most ICU's. No special equipment is required. A very good training video is available at www.nejm.org/doi/full/10.1056/NEJMoa1214103.
2. Were all clinically important outcomes considered?
	The authors evaluated a wide range of clinically important secondary outcomes including changes in oxygenation and adverse events (eg VAP, pressure ulcers, obstruction of ETT, unplanned extubation, unplanned removal of CVC or arterial lines, unplanned removal of chest tubes, pneumothorax or cardiac arrest).
3. Are the benefits worth the harms and costs?
	The estimated number needed to treat to save 1 life was 11. Whilst there was an increase in complications such as the risk of pressure ulcers, temporary obstruction of the ETT and dislodgement of thoracotomy tubes in patients positioned prone, ultimately these complications are manageable. There is minimal cost associated with proning, no new or special equipment is required for the procedure or to manage the prone patient.
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