Decreased chemosensitivity and improvement of sleep apnea by nocturnal hemodialysis

Background: Sleep apnea occurs in Lip 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 apnea and non-apneic groups based on apnea hypopnea index >= 15/h at baseline ( 17 apneics and 7 nonapneics), and the apneic group was further divided into "responders" and "non-responders" based on a significant reduction in AM 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. (C) 2007 Elsevier B.V. All rights reserved.