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 (PTP^pes) and occlusion (PTP^occl), as shown both by the regression analysis (  A ; PTP^occl= 0.95 · PTP^pes+ 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)