Fig. 4. Each point in the plot represents the pressure–time product (PTP) values obtained in the 11 measurement sequences. A tight correlation was found between the values derived from esophageal pressure (PTPpes) and occlusion (PTPoccl), as shown both by the regression analysis ( A ; PTPoccl= 0.95 · PTPpes+ 0.13, r = 0.96, P < 0.001) and by the Bland and Altman plot ( B ; 95% confidence interval, 1.94 and −1.61 cm H2O · s)