Influence of Lung and Chest Wall Compliances on Transmission of Airway Pressure to the Pleural Space in Critically Ill Patients

Nineteen patients with acute respiratory failure were divided into three groups according to their total compliance (CT). Transmission of airway pressure to the pleural space was then evaluated by measurement of esophageal pressure at both end-expiration and end-inspiration, and at three levels of PEEP. Chest wall (CW) and lung complicance (CL) were also calculated from simultaneous measurements of lung volume changes induced by tidal delivery. In group 1 (CT greater than 45 ml/cmH2O), 37 percent of airway pressure was transmitted to pleural space. In group 2 (CT between 45 and 30 ml/cmH2O), 32 percent of airway pressure was transmitted to the pleural space. In group 3 (CT less than 30 ml/cmH2O), only 24 percent of airway pressure was transmitted to the pleural space. These differences are statistically significant (p