[Prone position in the adult respiratory distress syndrome]

Acute respiratory distress syndrome (ARDS) has been a subject of research in the recent decades since it was defined in the seventies. ARDS is now known to be triggered by pulmonary and non-pulmonary insults which allow chemical agents to be released in the lungs. The resulting damage to the alveolar-capillary membrane causes an impaired ventilation and oxygenation. The aim of the present bibliographic review is to describe all the theories that have been proposed since 1974 to explain how the prone position enhances oxygenation in ARDS patients. Current thought amongst researchers includes how the prone position could improve the functional residual capacity, the ventilation/perfusion ratio, the mechanics of lung, diaphragmatic and thoracic movement, the ability to clear secretions, and the release of the lungs from weight of the mediastinal structures. The literature suggests using the prone position in the early stages of ARDS; however it has not been concluded how long prone position should be maintained in order to achieve the best oxygenation levels. The results of the studies reviewed revealed that 50-80% of the patients experienced significant improvement of oxygenation with the prone position. However, no study has shown that the prone position significantly reduces mortality. It is concluded that further investigations are necessary to understand how the prone position affects the lungs, what group of patients respond to this treatment, what duration and frequency of proning is most beneficial to reduce mortality, and how to effectively nurse patients who are in the prone position.