This study entitled "Prone Positioning in Severe Acute Respiratory Distress Syndrome" was published in 2013 and its aim was to evaluate the effect of early application of prone positioning on outcomes of patients with severe ARDS.
It was a multicentre, prospective, randomised controlled trial mainly in French Hospitals.
The primary outcome was 28 day mortality.
Recruited patients had to have severe ARDS, as defined in the Berlin definition, and FiO2 of at least 0.6, a PEEP of at least 5 and tidal volume target of 6ml/kg.
The patients, once selected, were allowed a stabilisation period of 24 hours then proned within the first hour of randomisation and placed in the prone position for at least 16 hours per session. Ventilation was delivered via volume controlled ventilation with the aim not to get the peak pressures higher than 30cm and for the pH to be between 7.2-7.45.
There were many reasons for stopping proning-
- If within 4 hours after the patient was supined any of the following were met- Ratio equal to or greater than 150, PEEP equal to or greater than 10 and FiO2 equal to or greater than 0.6
- or a decrease in the ratio of greater than 20%
- Main stem bronchus intubation
- ETT obstruction
- sats < 85% or PaCO2 > 55mmhg for 5 mins when FiO2 was 1.0
- Cardiac arrest
- Heart rate < 30
- BP systolic < 60 for 5 mins.
Otherwise proning was applied for a minimum of 28 days.
Pneumonia was the main cause followed by H1N1. Average number of prone sessions was 4 (+/- 4) per patient with the average duration of 17 hours (+/- 3).
Ratio was higher in the prone group at 3 and 5 days versus the supine group whereas PEEP and FiO2 were lower.
Mortality at 28 days was 16% in the prone group and 32.8% in the non-proned group.
This persisted to day 90 and remained even if adjusting for SOFA score, NMBs and vasopressors. rate of successful extubations was also higher in the prone group.
The authors do acknowledge some weaknesses to the study. Firstly it is mainly French based. Some of the data regarding the excluded patients was not always sent to them. They did not assess the affects of fluid balance or catecholamines and an imbalance between SOFA, vasopressors and NMBs could have influenced the results.
Another possible factor, more applicable back in 2013 than now, is the fact that the centres used were all very experienced in the use of proning patients and the difficulties that go with it.
The authors conclude-
In patients with severe ARDS, early application of prolonged prone-positioning sessions significantly decreased 28-day and 90-day mortality.