title: Sleep-disordered breathing with nighttime hypocapnia relates to daytime enhanced ventilatory response to exercise in patients with heart disease.
abstract: BACKGROUND
  Sleep-disordered breathing (SDB) induces nighttime disturbance of arterial gases, such as carbon dioxide. However, it is still unclear whether nighttime SDB-related gas abnormality is related to respiratory dysregulation in daytime. Therefore, we examined the relationship between the arterial partial pressure of carbon dioxide (PaCO(2)) at nighttime and the respiratory response to exercise in daytime.
  
  
  METHODS
  Eighteen men (age, mean ± SD; 55 ± 11 years) with heart disease underwent multichannel respiratory monitoring through the night with transdermal measurement of PaCO(2) (PtcCO(2)) reflecting PaCO(2) and a cardiopulmonary exercise test in daytime. The ventilatory equivalent (VE)/carbon dioxide production (VCO(2)) slope as an index of ventilatory response to exercise and peak oxygen consumption (VO(2)) were obtained with a cardiopulmonary exercise test.
  
  
  RESULTS
  Of the 18 patients, 10 patients had obstructive SDB, 5 had central SDB, and 3 patients did not have SDB. The mean apnea-hypopnea index was 21 ± 17. Minimum nighttime saturation of O(2) was positively correlated with peak VO(2), but not with VE/VCO(2). Nighttime PtcCO(2) was not correlated with peak VO(2) but was negatively correlated with the VE/VCO(2) slope of the daytime cardiopulmonary exercise test (r=-0.53).
  
  
  CONCLUSIONS
  Nighttime lowering of PaCO(2) in SDB is related to an abnormal ventilatory response to exercise testing in the daytime. This finding suggests that nighttime hyperventilation in SDB alters both nighttime and daytime pathophysiological conditions in patients with heart disease.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Nippon Medical School, Tokyo, Japan. fukuma@nms.ac.jp
authors.forename: Nagaharu
authors.initials: N
authors.lastname: Fukuma
authors.forename: Hiroko
authors.initials: H
authors.lastname: Hayashi
authors.forename: Juri
authors.initials: J
authors.lastname: Sugaya
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Aida
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Kato
authors.forename: Kazuyo
authors.initials: K
authors.lastname: Kato
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kato
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takahashi
authors.forename: Kyoichi
authors.initials: K
authors.lastname: Mizuno
mesh_terms: D000328:Adult; D000368:Aged; D001158:Arteries / Q000502:physiology; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D015444:Exercise / Q000502:physiology*; D006331:Heart Diseases / Q000503:physiopathology*; D006801:Humans; D016857:Hypocapnia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D010313:Partial Pressure; D012123:Pulmonary Ventilation / Q000502:physiology; D012891:Sleep Apnea Syndromes / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide