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 ef ficiency of the diaphragm while the abdomen was filled with dialysate and while it was empty. Maximum transdiaphragmatic pressure (Pdi(max)) served as parameter for diaphragmatic strength; diaphragmatic efficie ncy was assessed by simultaneously monitoring transdiaphragmatic press ure (Pdi) and diaphragmatic electromyogram (EMGdi) during room-air bre athing and hyperoxic CO2-rebreathing. After instilling dialysate, Pdi( max) increased from 76.7 +/- 12.1 cmH(2)O to 92.2 +/- 16.3 cmH(2)O (P < 0.05). While the slopes of the regression lines relating minute vent ilation (VE) to arterial CO2 tension, and the change in VE for a given change in Pdi during hypercapnic rebreathing were similar in both sta tes, the slope of EMGdi vs Pdi was significantly steeper when the abdo men was filled (P < 0.05). The increase in Pdi(max) observed in the fi lled 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.