Fig. 8

Method of calculating PTP. Applying permission to reprint from [21] with permission from Daedalus Enterprises; permission conveyed through Copyright Clearance Center, Inc. The upper curve is the time-flow curve, the middle curve is the time-airway pressure curve, and the lower curve is the time-esophageal pressure curve in the ventilated patient with spontaneous breathing. Pressure time product (PTP) can be calculated as the area bounded by the curve of the esophageal pressure in the negative direction during one inspiration (i.e., the pressure that inflates the lungs, color) and the straight line with thoracic compliance taken as the slope (i.e., the pressure that inflates the thorax), multiplied by respiratory rate