Amelioration of hemodialysis-induced fall in PaO2 with exercise

The hypoxemia of acetate hemodialysis may result from a decrease in alveolar ventilation (VA) related to a reduction in pulmonary carbon dioxide excretion (VCO2). To test this theory, ventilation was increased by exercise during dialysis on 6 patients and the effect on arterial oxygen tension (PaO2) measured. With hemodialysis the PaO2 fell from 102 to 92 mm Hg and with exercise rose to 102 mm Hg. These changes in PaO2 paralleled changes in VA and VCO2 induced by acetate dialysis and then exercise. The correlation coefficient between VA and VCO2 was 0.997. This close correlation suggests that CO2 load may be the main controlling factor for ventilation under these conditions. We conclude that the fall in PaO2 that occurs with acetate hemodialysis is due to decreased ventilation secondary to decreased VCO2 and that exercise can ameliorate the fall in PaO2 by increasing ventilation.