ABSTRACT
Key physiological principles Several theories have been proposed to explain the benefits gained from prone positioning; increased FRC, re-expansion of gravity-induced atelectasis, re-distribution of perfusion and alteration in diaphragmatic mechanics. However, most interest has been in the effects of prone positioning on V/Q relationships. • Placing a patient in the prone position may lead to beneficial changes in respiratory
mechanics (Pelosi et al. 1998). With positive pressure mechanical ventilation in the supine position (ribs and sternum free to move), preferential ventilation occurs in the nondependent/anterior regions of the lung. In the prone position however, the anterior/ sternal portion of the chest wall is ‘splinted’. This reduces regional compliance, and effects a more homogenous distribution of ventilation.
