Prone Positioning in Severe Acute Respiratory Distress Syndrome.
This review may be edited
Posted By: Elizabeth Sweetman
Posted Date: 28.05.2013
Title: Prone Positioning in Severe Acute Respiratory Distress Syndrome.
Authors: Guérin C, Reignier J, Richard JC, Beuret P, Gacouin A, Boulain T, Mercier E, Badet M, Mercat A, Baudin O, Clavel M, Chatellier D, Jaber S, Rosselli S, Mancebo J, Sirodot M, Hilbert G, Bengler C, Richecoeur J, Gainnier M, Bayle F, Bourdin G, Leray V, Girard R, Baboi L, Ayzac L; the PROSEVA Study Group.
Reference: N Engl J Med. 2013 May 20.
Link: Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract: Background Previous trials involving patients with the acute respiratory distress syndrome (ARDS) have failed to show a beneficial effect of prone positioning during mechanical ventilatory support on outcomes. We evaluated the effect of early application of prone positioning on outcomes in patients with severe ARDS.
Methods In this multicenter, prospective, randomized, controlled trial, we randomly assigned 466 patients with severe ARDS to undergo prone-positioning sessions of at least 16 hours or to be left in the supine position. Severe ARDS was defined as a ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (FiO2) of less than 150 mm Hg, with an FiO2 of at least 0.6, a positive end-expiratory pressure of at least 5 cm of water, and a tidal volume close to 6 ml per kilogram of predicted body weight. The primary outcome was the proportion of patients who died from any cause within 28 days after inclusion.
Results A total of 237 patients were assigned to the prone group, and 229 patients were assigned to the supine group. The 28-day mortality was 16.0% in the prone group and 32.8% in the supine group (P<0.001). The hazard ratio for death with prone positioning was 0.39 (95% confidence interval [CI], 0.25 to 0.63). Unadjusted 90-day mortality was 23.6% in the prone group versus 41.0% in the supine group (P<0.001), with a hazard ratio of 0.44 (95% CI, 0.29 to 0.67). The incidence of complications did not differ significantly between the groups, except for the incidence of cardiac arrests, which was higher in the supine group.
Conclusions In patients with severe ARDS, early application of prolonged prone-positioning sessions significantly decreased 28-day and 90-day mortality. (Funded by the Programme Hospitalier de Recherche Clinique National 2006 and 2010 of the French Ministry of Health; PROSEVA number, NCT00527813 .).
Are the Results Valid?
1. Was the assignment of patients to treatments randomized? ( Was allocation concealment maintained?)
Yes. Patients were randomly assigned to either the Prone study group or Supine study group via a centralised web based management system.
Patients assigned to the Prone group were required to be turned within one hour after randomisation. After turning prone group patients could remain in a prone group patients for at least 16 consecutive hours. The proning strategy was applied everyday up to day 28 unless the patients met previously noted criteria for stopping proning (page 3, protocol section). Supine group patients remained in a semirecumbent position.
2. Were all patients who entered the trial properly accounted for and attributed at its conclusion?
2a. Was followup complete?
All patients were accounted for at the completion of the trial, figure 1, page 4.
Three patients in the Prone group were excluded from analysis due to eligibility reasons and five patients in the Supine group were excluded from analysis due to eligibility and consent issues.
2b. Were patients analyzed in the groups to which they were randomized?
Yes. All enrolled patients were analysed in the groups to which they were randomised.
3. Were patients, health workers, and study personnel blind to treatment?
The patients, health care workers and study personnel were not blinded to treatment group.
4. Were the groups similar at the start of the trial?
Mostly yes.
As per table 1, page 5 (no p values provided); Patients in the Supine group had a slightly higher SOFA score than patients in the Prone group (10.4 +_ 3.4 vs 9.6 +_ 3.2).
A higher percentage of patients in the Supine group were on vasopressors compared to patients in the Prone group(83.0% vs 72.6%).
A lower percentage of patients in the Supine group were on neuromuscular blockers compared to patients in the Prone group(82.3% vs 91.0%).
As per table 2, ventilator settings, ABG measures and respiratory system mechanics were similar between groups
5. Aside from the experimental intervention, were the groups treated equally?
Essentially yes.
There was a trend towards the higher use of nitric oxide in the Supine group verse Prone group (15.7% vs 9.7%, p = 0.05) and significantly more patients in the Supine group than in the Prone Group received Almitrine Bismesylate (6.6% vs 2.5%, p = 0.04). (adjuctive therapies section, pg 6)
What are the Results?
1. How large was the treatment effect?
Primary Outcome (Table 3, p.7) -
Mortality at Day 28 :
Mortality at Day 28 significantly lower in the Prone group compared to the Supine group(16.8% vs 32.8%, P <0.001)
Secondary Outcomes (Table 3, p. 7) -
Mortality at Day 90 :
Mortality at Day 90 significantly lower in the Prone group compared to the Supine group(23.6% vs 41.0%, P <0.001).
**Note: As per table 3, after adjustment of SOFA score, neuromuscular blockers and vasopressors, mortality at Day 28 and Day 90 remained statistically significant in favour of a reduction of mortality in the Prone group.
All other secondary outcomes (Table 23) not significant.
2. How precise was the estimate of the treatment effect?
Primary Outcome -
Mortality at Day 28 :
Prone vs Supine Group unadjusted 95% CI 0.25 - 0.63
Secondary Outcome -
Mortality at Day 90 :
Prone vs Supine Group unadjusted 95% CI 0.29 - 0.67
Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care?
2. Were all clinically important outcomes considered?
Yes major important outcomes were considered.
Quality of life and physical function measures could have been considered.
3. Are the likely treatment benefits worth the potential harms and costs?
In this trial proning of severe ARDS patients was found to be beneficial to patients compared to keeping patients in a supine semirecumbent position. There were also no added complications for patients in the Prone Group.
Proning of severe ARDS patients within this trial was done within ICUs who were very familiar with this intervention and who used it as part of their daily practice. For those ICUs who do not routinely prone severe ARDs patients, this trial provides a procotol to guide practitioners which patients to prone, when and when not to prone and how long to prone for.
Severe ARDs patients may benefit from being proned in the same manner and under the same guidelines as patients within this study.

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Prone Positioning in Severe Acute Respiratory Distress Syndrome.

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