Diaphragmatic function in patients on continuous ambulatory peritoneal dialysis.

We investigated 8 patients undergoing continuous ambulatory peritoneal dialysis (CAPD) for diaphragmatic strength and the neuromechanical efficiency of the diaphragm while the abdomen was filled with dialysate and while it was empty. Maximum transdiaphragmatic pressure (Pdimax) served as parameter for diaphragmatic strength; diaphragmatic efficiency was assessed by simultaneously monitoring transdiaphragmatic pressure (Pdi) and diaphragmatic electromyogram (EMGdi) during room-air breathing and hyperoxic CO2-rebreathing. After instilling dialysate, Pdimax increased from 76.7 +/- 12.1 cmH2O to 92.2 +/- 16.3 cmH2O (P < 0.05). While the slopes of the regression lines relating minute ventilation (VE) to arterial CO2 tension, and the change in VE for a given change in Pdi during hypercapnic rebreathing were similar in both states, the slope of EMGdi vs Pdi was significantly steeper when the abdomen was filled (P < 0.05). The increase in Pdimax observed in the filled state may suggest an adaptive rightward shift in the diaphragm's force-length relationship in CAPD patients, although this mechanism is insufficient to prevent a reduction of neuromechanical efficiency of the diaphragm.