Ventilation in the prone position in patients with acute lung injury/acute respiratory distress syndrome

Purpose of review To contrast the beneficial effects of the prone position on the lungs and the lack of proven clinical benefits on patient outcome. Recent findings Recent human investigations in acute respiratory distress syndrome have shown that the prone position was able to abolish tidal expiratory flow limitation, to improve oxygenation in the case of localized infiltrates, to allow for reducing positive end-expiratory pressure level, and to reduce lung stress and strain. Experimental studies have confirmed that distribution of ventilation was more homogeneous in the prone position but showed that positive end-expiratory pressure affected ventilation distribution differently in the prone and in the supine position. Experimental work has also shown that proning reduced strains imposed on the lungs and made them more homogeneously distributed. Finally, one recent large randomized controlled trial of systematic proning in hypoxemic patients showed no reduction in mortality but less ventilator-associated pneumonia incidence in the prone position group. Summary The prone position is not systematically used in hypoxemic patients. Patients who could benefit from prone position sessions are those with the most severe acute respiratory distress syndrome and those with dorsal lung infiltrates. Whether this can be translated into improvement in patient outcome has yet to be tested in clinical trials.