Fig. 3. Pressure–volume curves taken in the supine position (  A ) and in the beach chair position (  B ). In each panel, values taken at baseline are shown as  circles , and those obtained during pneumoperitoneum are shown as  squares . Closed symbols indicate values at zero end-expiratory pressure, and  open symbols indicate those at 10 cm H²O positive end-expiratory pressure. To compare curves, each one starts on the y-axis from the volume corresponding to the mean value of end-expiratory lung volume measured by helium dilution technique.