Prone ventilation following witnessed pulmonary aspiration: the effect on oxygenation.

OBJECTIVE: Pulmonary aspiration is a significant cause of admission to the ITU and is associated with significant morbidity and mortality. Aspiration in the supine position produces posterior collapse/consolidation, similar to that seen in ALI/ARDS patients. Prone positioning has been shown to improve oxygenation in ALI/ARDS, but no studies have been performed on pulmonary aspiration. DESIGN: A prospective crossover study. SETTING: Twelve-bed ITU. PATIENTS AND PARTICIPANTS: Eleven patients admitted to ITU with respiratory failure secondary to witnessed pulmonary aspiration requiring ventilation and an FIO(2) >0.50 after 12 h. INTERVENTIONS: Patients were placed in a prone position for 8 h and then turned supine for 8 h. Prone positioning was repeated if the FIO(2) remained >0.50. Ventilator settings were not altered in the study period. MEASUREMENTS AND RESULTS: Arterial blood gas analysis was performed every 2 h. The PaO(2)/FIO(2) gradient was calculated. Oxygenation improved on turning prone, with a significant increase in the PaO(2)/FIO(2) ratio ( P<0.01). There was a fall in this gradient on return to the supine position. There was a significant improvement in oxygenation on turning prone for the second period ( P<0.01). Overall, there was a significant improvement in the PaO(2)/FIO(2) ratio in the final supine position when compared to the first ( P<0.05). CONCLUSION: This study demonstrates a significant improvement in oxygenation in the prone position in pulmonary aspiration. Early prone positioning in patients with pulmonary aspiration requiring ventilation may improve oxygenation by altering V/Q relationships similarly to ARDS, but also may aid drainage of secretions, opening up alveoli and preventing progression to established pneumonitis.