Decreased chemosensitivity and improvement of sleep apnea by nocturnal hemodialysis.

BACKGROUND

Sleep apnea occurs in up to 50% of patients with end-stage renal disease and is improved by nocturnal hemodialysis. We hypothesized that its pathogenesis is related to changes in chemoreflex responsiveness.

METHODS

Twenty-four patients receiving conventional hemodialysis (4 h/day, 3 times/week) had overnight polysomnography and measurement of the ventilatory response to carbon dioxide during isoxic hypoxia and hyperoxia using a modified rebreathing technique. Measurements were repeated following conversion from conventional to nocturnal hemodialysis (8 h/night, 3-6 nights/week). Patients were divided into apneic and non-apneic groups based on apnea-hypopnea index > or =15/h at baseline (17 apneics and 7 non-apneics), and the apneic group was further divided into "responders" and "non-responders" based on a significant reduction in AHI at follow-up.

RESULTS

Conversion from conventional to nocturnal hemodialysis was associated with a decrease in the ventilatory sensitivity to hypercapnia during hyperoxia in responders (3.2+/-1.0 vs. 2.3+/-1.3 L/min/mmHg) but not in non-responders (2.8+/-1.3 vs. 2.9+/-1.6 L/min/mmHg). The change in ventilatory sensitivity was correlated with the change in apnea-hypopnea index in all apneic patients (r=.528, p=0.029).

CONCLUSIONS

Improvement of sleep apnea following conversion from conventional to nocturnal hemodialysis is associated with a decrease in chemoreflex responsiveness. This finding suggests that increased chemoreflex responsiveness contributes to the pathogenesis of sleep apnea in some patients with end-stage renal disease.