Impaired water handling in chronic obstructive airways disease

The response to a standard water load (20 ml/kg body weight) was studied in 20 patients with chronic obstructive airways disease and in 13 healthy subjects. The percentage of the water load excreted in four hours was significantly lower in the patients (mean 51%) than in the controls (mean 106%). The maximum urine flow, osmolar clearance, free water clearance, and creatinine clearance were also significantly reduced in the patients. There was a significant inverse correlation between the percentage of load passed and the arterial PCO(2) (r = -0.798). Among the several possible causes of the reduced excretion of water which are discussed is a direct effect of hypercapnia.