title: Nocturnal continuous positive airway pressure improves ventilatory efficiency during exercise in patients with chronic heart failure.
abstract: OBJECTIVE
  Chronic heart failure is closely related to impaired cardiorespiratory reflex control, including decreased ventilatory efficiency during exercise (Ve/Vco(2)-slope) and central sleep apnea (CSA). Continuous positive airway pressure (CPAP) and nocturnal oxygen therapy alleviate CSA. The aim of the present study was to compare the effects of nocturnal CPAP and oxygen therapy on Ve/Vco(2)-slope.
  
  
  METHODS
  Prospective controlled trial at a university hospital.
  
  
  METHODS
  Twenty-six stable patients with chronic heart failure and CSA.
  
  
  METHODS
  Ten patients received nocturnal oxygen, and 16 patients were assigned to CPAP treatment. At baseline and after 12 weeks of treatment, symptom-limited cardiopulmonary exercise testing was performed on a cycle ergometer. Expiratory gas was analyzed breath by breath for evaluation of ventilation and ventilatory efficiency in combination with arteriocapillary blood gas analysis during rest and exercise.
  
  
  RESULTS
  CPAP treatment significantly reduced the Ve/Vco(2)-slope (31.2 +/- 1.6 vs 26.2 +/- 1.0, p = 0.005) and improved the left ventricular ejection fraction (LVEF) [31.7 +/- 2.6% vs 35.7 +/- 2.7%, p = 0.041]. CPAP treatment significantly reduced the apnea-hypopnea index (AHI) [35.9 +/- 4.0/h vs 12.2 +/- 3.6/h, p = 0.002]. Peak oxygen consumption (Vo(2)) [16.2 +/- 1.1 L/min/kg vs 16.3 +/- 1.2 L/min/kg, p = 0.755] remained similar after CPAP treatment. Oxygen therapy reduced the AHI (28.8 +/- 3.2/h vs 8.7 +/- 4.1/h, p = 0.019), but did not improve exercise capacity (peak Vo(2), 15.4 +/- 1.5 L/min/kg vs 15.6 +/- 1.9 L/min/kg, p = 0.760), LVEF (30.9 +/- 2.4% vs 32.5 +/- 2.3%, p = 0.231), or the Ve/Vco(2)-slope (30.0 +/- 1.5 vs 29.8 +/- 1.5, p = 0.646).
  
  
  CONCLUSIONS
  Nocturnal CPAP and oxygen therapy alleviate CSA to a similar degree. Only CPAP therapy may improve ventilatory efficiency during exercise and may have favorable effects on LVEF. Therefore, our data suggest that CPAP is advantageous compared to oxygen in the treatment of CSA in patients with chronic heart failure.
authors.affiliation: Department of Internal Medicine II, University of Regensburg, Germany. michael.arzt@utoronto.ca
authors.forename: Michael
authors.initials: M
authors.lastname: Arzt
authors.forename: Martina
authors.initials: M
authors.lastname: Schulz
authors.forename: Roland
authors.initials: R
authors.lastname: Wensel
authors.forename: Sylvia
authors.initials: S
authors.lastname: Montalvàn
authors.forename: Friedrich C
authors.initials: FC
authors.lastname: Blumberg
authors.forename: Günter A J
authors.initials: GA
authors.lastname: Riegger
authors.forename: Michael
authors.initials: M
authors.lastname: Pfeifer
mesh_terms: D000368:Aged; D002908:Chronic Disease; D045422:Continuous Positive Airway Pressure; D005080:Exercise Test; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008875:Middle Aged; D010101:Oxygen Consumption; D010102:Oxygen Inhalation Therapy; D017286:Polysomnography; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D013318:Stroke Volume