Effect of chronic renal failure on respiratory muscle strength

In 10 patients with chronic renal failure (CRF), undergoing hemodialysis, we studied respiratory muscle strength and endurance. The data obtained was compared with those acquired from 10 age-, sex-, weight- and height-matched normal volunteers. Maximal static inspiratory pressures (PImax) measured at residual volume and maximal static expiratory pressure (PEmax) measured at total lung capacity were significantly lower in the CRF group, 58.2 +/- (SD)24.9 and 50.8 +/- (SD)24.2% of predicted, respectively (p less than 0.005, p less than 0.01). There was a significant correlation between PImax and PEmax (r = 0.827, p less than 0.001), indicating similar involvement of both inspiratory and expiratory muscle groups. Maximal voluntary ventilation (MVV), although 84.4% of the predicted value in the CRF group, was significantly lower than in the control group, where it was 114% of predicted (p less than 0.001). MVV also correlated significantly with PImax and PEmax (r = 0.764, p less than 0.001 and r = 0.807, p less than 0.001, respectively). All but one CRF patient had elevated erum inorganic phosphorus levels, and a significant correlation was found between the serum inorganic phosphorus levels and PImax and PEmax (r = 0.718, p less than 0.001). These data indicate that there is an impairment of respiratory muscle strength and endurance in patients with CRF which may predispose the patient to respiratory muscle fatigue.