Effect of prone positioning on the survival of patients with acute respiratory failure
This review may be edited
Posted By: Vatsal Kothari
Posted Date: 17/09/03
Title: Effect of prone positioning on the survival of patients with acute respiratory failure
Authors: Gattinoni L,Tognoni G,Pesenti A et al
Reference: NEJM Vol 345,No 8,Aug 23,2001
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Abstract: Background Although placing patients with acute respiratory failure in a prone (face down) position improves their oxygenation 60 to 70 percent of the time, the effect on survival is not known.

Methods In a multicenter, randomized trial, we compared conventional treatment (in the supine position) of patients with acute lung injury or the acute respiratory distress syndrome with a predefined strategy of placing patients in a prone position for six or more hours daily for 10 days. We enrolled 304 patients, 152 in each group.

Results The mortality rate was 23.0 percent during the 10-day study period, 49.3 percent at the time of discharge from the intensive care unit, and 60.5 percent at 6 months. The relative risk of death in the prone group as compared with the supine group was 0.84 at the end of the study period (95 percent confidence interval, 0.56 to 1.27), 1.05 at the time of discharge from the intensive care unit (95 percent confidence interval, 0.84 to 1.32), and 1.06 at six months (95 percent confidence interval, 0.88 to 1.28). During the study period the mean (±SD) increase in the ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen, measured each morning while patients were supine, was greater in the prone than the supine group (63.0±66.8 vs. 44.6±68.2, P=0.02). The incidence of complications related to positioning (such as pressure sores and accidental extubation) was similar in the two groups.

Conclusions Although placing patients with acute respiratory failure in a prone position improves their oxygenation, it does not improve survival.

Are the Results Valid?
1. Was the assignment of patients to treatments randomized? ( Was allocation concealment maintained?)
Yes. Patients were recruited from 28 intensive care units in Italy and 2 in Switzerland and were randomly assigned to a supine or prone group. Randomization was conducted centrally by telephone on a 24-hour-a-day, 7-day-a-week basis and was based on a permuted-block algorithm, which allowed stratification according to the intensive care unit.
2. Were all patients who entered the trial properly accounted for and attributed at its conclusion?
2a. Was followup complete?
Yes.The status at 183 days was known for all but seven patients (four in the prone group and three in the supine group).
2b. Were patients analyzed in the groups to which they were randomized?
Yes. There was no crossover between the groups.
3. Were patients, health workers, and study personnel blind to treatment?
No. This would not have been possible given the logistics of the protocol and the intervention.
4. Were the groups similar at the start of the trial?
Yes. There were no significant differences in the prognostic factors between the two groups.
5. Aside from the experimental intervention, were the groups treated equally?
What are the Results?
1. How large was the treatment effect?
Time       % of Deaths   ARR
           Control Prone
10 days      25      21.1     3.9 (no significant difference)

Discharge   48      50.7     -2.7 (no significant difference)

6 months     58.6    62.5    -3.9 (no significant difference)

2. How precise was the estimate of the treatment effect?
Time    Relative Risk of Death    95% Confidence intervals
        due to proning
10 days      0.84    0.56-1.27

Discharge      1.05    0.84-1.32

6 months      1.06    0.88-1.28

NB - this trial suggests evidence of harm in longer term outcomes (Dishcarge and 6 months).

Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care?
This multi-centre study addresses a common problem in most ICU'S.
2. Were all clinically important outcomes considered?
Yes. Both the effects of the prone position on respiratory parameters and the complications ensuing from placing in the prone position.
3. Are the likely treatment benefits worth the potential harms and costs?
Unsure. Because this negative study was designed with 80% power, we are unable to conclude that there is no benefit from proning. However it is very important to note that the longer term outcomes suggest a possible increased mortality rate in patients who were proned.

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Effect of prone positioning on the survival of patients with acute respiratory failure

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