EFFECT OF OXYGEN ON BREATHING IRREGULARITIES DURING HEMODIALYSIS IN PATIENTS WITH CHRONIC UREMIA

Hypoxaemia and breathing irregularities have been shown to occur durin g haemodialysis in patients with chronic renal failure. This study exa mined the role of hypoxia in the genesis of the irregular breathing du ring haemodialysis. The ventilatory patterns using respiratory inducta nce plethysmography and arterial blood gases mere studied in seven mal es with chronic renal failure on long-term haemodialysis. The study wa s carried out before and during dialysis on one day without (D1) and a nother day with intranasal oxygen at 4 L.min(-1) (D2). On D1, mean (SD ) arterial oxygen tension (Pa,O-2) fell 1.9 (0.9) kPa (p<0.001) and me an minute ventilation (V'E) fell 19 (1.1) L.min(-1) (p<0.01) during di alysis. The arterial carbon dioxide tension (Pa,CO2) did not show a si gnificant decrease (4.7 (0.2) kPa before and 4.6 (0.2) kPa during dial ysis). Cumulative number of apnoeas was 64 and the coefficients of var iation (COV) of respiratory frequency (fR) and tidal volume (VT) were 29.6 (11.9) and 38.2 (11.9)%, respectively, On D2, mean Pa,O-2 remaine d stable (20.4 (4.1) kPa before, 213 (4.1) kPa during dialysis), There was no significant change in mean V'E (6.4 (0.9) L.min(-1) before, 5. 5 (0.5) L.min(-1) during dialysis), Pa,CO2 decrease was not significan t but the fall was greater (4.8 (0.1) kPa before, 4.5 (0.5) kPa during dialysis), Cumulative number of apnoeas was 94 and the COVs of fR and VT were 35.8 (5.1) and 40.5 (11.3)%, respectively. Oxygen administrat ion did not significantly affect the haemodialysis-induced changes in ventilation and breathing pattern, despite a significant protective ef fect from the fall in arterial oxygen tension, It was concluded that t he fall in arterial oxygen tension is not the main determinant of brea thing irregularities during haemodialysis.