title: Interval hypoxic training improves autonomic cardiovascular and respiratory control in patients with mild chronic obstructive pulmonary disease.
abstract: OBJECTIVE
  Chronic obstructive pulmonary disease (COPD) is associated with cardiac autonomic nervous system dysregulation. This study evaluates the effects of interval hypoxic training on cardiovascular and respiratory control in patients with mild COPD.
  
  
  METHODS
  In 18 eucapnic normoxic mild COPD patients (age 51.7 +/- 2.4 years, mean +/- SEM), randomly assigned to either training or placebo group, and 14 age-matched healthy controls (47.7 +/- 2.8 years), we monitored end-tidal carbon dioxide, airway flow, arterial oxygen saturation, electrocardiogram, and continuous noninvasive blood pressure at rest, during progressive hypercapnic hyperoxia and isocapnic hypoxia to compare baroreflex sensitivity to hypoxia and hypercapnia before and after 3 weeks of hypoxic training. In double-blind fashion, both groups received 15 sessions of passive intermittent hypoxia (training group) or normoxia (placebo group). For the hypoxia group, each session consisted of three to five hypoxic (15-12% oxygen) periods (3-5 min) with 3-min normoxic intervals. The placebo group inhaled normoxic air.
  
  
  RESULTS
  Before training, COPD patients showed depressed baroreflex sensitivity, as compared with healthy individuals, without evident chemoreflex abnormalities. After training, in contrast to placebo group, the training group showed increased (P < 0.05) baroreflex sensitivity up to normal levels and selectively increased hypercapnic ventilatory response (P < 0.05), without changes in hypoxic ventilatory response.
  
  
  CONCLUSIONS
  Eucapnic normoxic mild COPD patients already showed signs of cardiovascular autonomic abnormalities at baseline, which normalized with hypoxic training. If confirmed in more severe patients, interval hypoxic training may be a therapeutic strategy to rebalance early autonomic dysfunction in COPD patients.
authors.affiliation: Department of Sport Science, Medical Section, University of Innsbruck, Innsbruck, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Haider
authors.forename: Gaia
authors.initials: G
authors.lastname: Casucci
authors.forename: Tobias
authors.initials: T
authors.lastname: Linser
authors.forename: Martin
authors.initials: M
authors.lastname: Faulhaber
authors.forename: Hannes
authors.initials: H
authors.lastname: Gatterer
authors.forename: Guenter
authors.initials: G
authors.lastname: Ott
authors.forename: Armin
authors.initials: A
authors.lastname: Linser
authors.forename: Igor
authors.initials: I
authors.lastname: Ehrenbourg
authors.forename: Elena
authors.initials: E
authors.lastname: Tkatchouk
authors.forename: Martin
authors.initials: M
authors.lastname: Burtscher
authors.forename: Luciano
authors.initials: L
authors.lastname: Bernardi
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001945:Breathing Exercises; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000628:therapy; D012119:Respiration