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.