Method and interpretation of the pressure volume curve in patients with acute respiratory distress syndrome

The pressure volume curve of the respiratory system is a useful tool that has been proposed to assess respiratory mechanics impairment exhibited by patients with the acute respiratory distress syndrome. Acute respiratory distress syndrome is characterized by a significant reduction in lung compliance mainly due to the reduction in healthy lung volume. During mechanical ventilation, lung inflation results in recruitment of previously nonaerated alveoli and a concomitant distension of healthy lung units. This phenomenon has been shown to be the main determinant of ventilatory-induced lung injuries. The lower inflection point, which is present on the lower part of the pressure volume curve, and the upper inflection point have been proposed as an insight to both recruitment and overdistension, respectively. This interpretation of the curve has led to the concept of lung protective ventilation. Nevertheless, specific rules governing recruitment and distension are only now emerging from the abundant literature resulting from more than 30 years of physiological research. The interpretation and the utility of the pressure volume curve should, therefore, be reconsidered in the light of recent knowledge. Copyright © 2005 by Lippincott Williams & Wilkins.