[Effects of lung volume levels and trapidil on transdiaphragmatic pressure in young healthy subjects].

Effects of lung volume levels, and effect of intravenous administration of Trapidil on the maximal force developed by the diaphragm were investigated by the measurement of transdiaphragmatic pressure (Pdi) in 10 healthy young subjects. To evaluate transdiaphragmatic pressure, delta Pdimax was used. delta Pdimax was calculated by the subtraction of the transdiaphragmatic pressure at FRC (Pdi FRC) from the maximal transdiaphragmatic pressure (Pdimax) at each lung-volume level. Regardless of the administration of Trapidil, delta Pdimax was highest at FRC in each subject. When Trapidil was administered, Pdimax increased in cases where absolute Pdimax FRC was initially low. The relation between changes of delta Pdimax at FRC after Trapidil administration and delta Pdimax showed significant linear correlation (r = -0.85, p less than 0.002). These results suggest that FRC is the most adequate lung volume level to produce an effective transdiaphragmatic pressure, and that Trapidil increases the muscle force of the diaphragm in cases where the force is initially low in young healthy subjects.