title: Nocturnal rostral fluid shift: a unifying concept for the pathogenesis of obstructive and central sleep apnea in men with heart failure.
abstract: BACKGROUND
  Obstructive sleep apnea (OSA) and central sleep apnea are common in patients with heart failure. We hypothesized that in such patients, severity of OSA is related to overnight rostral leg fluid displacement and increase in neck circumference, severity of central sleep apnea is related to overnight rostral fluid displacement and to sleep Pco(2), and continuous positive airway pressure alleviates OSA in association with prevention of fluid accumulation in the neck.
  
  
  RESULTS
  In 57 patients with heart failure (ejection fraction <or=45%), we measured change in leg fluid volume and neck circumference before and after polysomnography, and we measured transcutaneous Pco(2) during polysomnography. Patients were divided into an obstructive-dominant group (>or=50% of apneas and hypopneas obstructive) and a central-dominant group (>50% of events central). Patients with OSA received continuous positive airway pressure. In obstructive-dominant patients, there were inverse relationships between overnight change in leg fluid volume and both the overnight change in neck circumference (r=-0.780, P<0.001) and the apnea-hypopnea index (r=-0.881, P<0.001) but not transcutaneous Pco(2). In central-dominant patients, the overnight reduction in leg fluid volume correlated inversely with the apnea-hypopnea index (r=-0.919, P<0.001) and the overnight change in neck circumference (r=-0.568, P=0.013) and directly with transcutaneous Pco(2) (r=0.569, P=0.009). Continuous positive airway pressure alleviated OSA in association with prevention of the overnight increase in neck circumference (P<0.001).
  
  
  CONCLUSIONS
  Our findings suggest that nocturnal rostral fluid shift is a unifying concept contributing to the pathogenesis of both OSA and central sleep apnea in patients with heart failure.
authors.affiliation: Toronto General Hospital/University Health Network, 9N-943, 200 Elizabeth St, Toronto, Ontario M5G 2C4, Canada.
authors.forename: Dai
authors.initials: D
authors.lastname: Yumino
authors.forename: Stefania
authors.initials: S
authors.lastname: Redolfi
authors.forename: Pimon
authors.initials: P
authors.lastname: Ruttanaumpawan
authors.forename: Mao-Chang
authors.initials: MC
authors.lastname: Su
authors.forename: Stephanie
authors.initials: S
authors.lastname: Smith
authors.forename: Gary E
authors.initials: GE
authors.lastname: Newton
authors.forename: Susanna
authors.initials: S
authors.lastname: Mak
authors.forename: T Douglas
authors.initials: TD
authors.lastname: Bradley
mesh_terms: D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000032:analysis; D002311:Cardiomyopathy, Dilated / Q000150:complications; D045422:Continuous Positive Airway Pressure; D005919:Glomerular Filtration Rate; D006333:Heart Failure / Q000150:complications*; D006801:Humans; D007866:Leg / Q000033:anatomy & histology; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000033:anatomy & histology; D017286:Polysomnography; D011187:Posture; D020182:Sleep Apnea, Central / Q000453:epidemiology* / Q000628:therapy*; D020181:Sleep Apnea, Obstructive / Q000453:epidemiology* / Q000628:therapy*; D013318:Stroke Volume
chemical_list: D002245:Carbon Dioxide