Elephant in the room?


By Jonathan Leung, Consultant EM.

Does high PEEP use in ARDS/ALI save life?
Over the years, I have been taught that high PEEP ventilation can save life in ARDA/ALI, but can also cause barotrauma. However, no one can tell me how good can high PEEP improve mortality. Hence, I have done a literature search on the topic and found a recent Cochrane review [2013, issue 6] and a meta-analysis in 2009 on the exact topic.

Cochrane Review [2013, issue 6]
Cochrane have included 7 studies compared high and low PEEP with 2565 participants. The authors have concluded PEEP did not reduce mortality before hospital discharge, in addition there is minimal increase of risk in barotrauma. Nonetheless, it have been shown to improve the participants’ oxygenation in first, third and seventh days.

Mortality before hospital discharge RR – 0.9 (0.81-1.01)
Mean PaO2/FiO2 – day1 41.31 higher (24.1-58.52)
Mean PaO2/FiO2 – day3 42.51 higher (25-60.02)
Mean PaO2/FiO2 – day7 24.77 higher (0.92lower – 50.45 higher)
Barotrauma RR-0.97 (0.66-1.42)
Ventilator-free days (only means) 1.89 more ventilator-free days
(3.58 lower- 7.36 higher)

Systematic review and Meta-analysis [Anaesthesiology 2009; 110:1098-105]
This meta- analysis have reviewed six trials with a total of 2,484 patients from 102 ICUs. The authors have concluded that high PEEP strategy may only have a clinically relevant independent mortality benefit, as they found a non-statistically significant mortality benefit.

Relative risk of death- 0.9 (C.I.0.72-1.02) p-value: 0.077
NNT – 22

Relative Risk of barotrauma in ARDS/ALI – 0.95 (C.I. 0.62-1.45, p=0.81)
NNH – 269

Both of the meta-analysis have a high degree of heterogeneity in the participants, as diagnostic criteria of ARDS and ALI have changed over the years.