title: Decreased chemosensitivity and improvement of sleep apnea by nocturnal hemodialysis.
abstract: 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.
authors.affiliation: Department of Medicine, University of Calgary, 1421 HSC, 3330 Hospital Drive NW, Calgary, Alta., Canada T2N 4N1.
authors.forename: Jaime M
authors.initials: JM
authors.lastname: Beecroft
authors.forename: James
authors.initials: J
authors.lastname: Duffin
authors.forename: Andreas
authors.initials: A
authors.lastname: Pierratos
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Chan
authors.forename: Philip
authors.initials: P
authors.lastname: McFarlane
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Hanly
mesh_terms: D000328:Adult; D000368:Aged; D002628:Chemoreceptor Cells / Q000502:physiology; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D007676:Kidney Failure, Chronic / Q000150:complications* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D006435:Renal Dialysis / Q000379:methods*; D012891:Sleep Apnea Syndromes / Q000150:complications* / Q000503:physiopathology / Q000517:prevention & control*