title: Relationship between obstructive sleep apnea and endogenous carbon monoxide.
abstract: Endogenous carbon monoxide (CO) levels are recognized as a surrogate marker for activity of heme oxygenase-1, which is induced by various factors, including hypoxia and oxidative stress. Few reports have evaluated endogenous CO in patients with obstructive sleep apnea (OSA). Whether OSA more greatly affects exhaled or blood CO is not known. Sixty-nine patients with suspected OSA were prospectively included in this study. Exhaled and blood CO were evaluated at night and morning. Blood and exhaled CO levels were well correlated both at night and morning (r = 0.52, P < 0.0001 and r = 0.61, P < 0.0001, respectively). Although exhaled CO levels both at night and morning significantly correlated with total sleep time with arterial oxygen saturation < 90% (ρ = 0.41, P = 0.0005 and ρ = 0.27, P = 0.024, respectively), blood CO levels did not correlate with any sleep parameter. Seventeen patients with an apnea and hypopnea index (AHI) < 15 (control group) were compared with 52 patients with AHI ≥ 15 (OSA group). Exhaled CO levels at night in the OSA group were significantly higher than in the control group (3.64 ± 1.2 vs. 2.99 ± 0.70 ppm, P < 0.05). Exhaled CO levels at night decreased after 3 mo of continuous positive airway pressure (CPAP) therapy in OSA patients (n = 36; P = 0.016) to become nearly the same level as in the control group (P = 0.21). Blood CO levels did not significantly change after CPAP therapy. Exhaled CO was positively related to hypoxia during sleep in OSA patients, but blood CO was not. Exhaled CO might better correlate with oxidative stress associated with OSA than blood CO.
  
  
  
  Endogenous carbon monoxide (CO) levels are recognized to be a surrogate marker of oxidative stress. No study has evaluated both exhaled and blood CO at the same time in obstructive sleep apnea (OSA) patients. Here we provide evidence that exhaled CO levels positively correlated with hypoxia during sleep in OSA patients, but blood CO levels did not, and that continuous positive airway pressure therapy significantly decreased exhaled CO levels in the OSA group, but did not significantly affect blood CO.
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan; and.
authors.forename: Masanori
authors.initials: M
authors.lastname: Azuma
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan; and.
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Murase
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan; and.
authors.forename: Ryo
authors.initials: R
authors.lastname: Tachikawa
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan; and.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hamada
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan; and.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsumoto
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan; and.
authors.forename: Takuma
authors.initials: T
authors.lastname: Minami
authors.affiliation: Department of Respiratory Care and Sleep Control Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Morito
authors.initials: M
authors.lastname: Inouchi
authors.affiliation: Department of Respiratory Care and Sleep Control Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Kiminobu
authors.initials: K
authors.lastname: Tanizawa
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan; and.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Handa
authors.affiliation: Department of Respiratory Care and Sleep Control Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Oga
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan; and.
authors.forename: Michiaki
authors.initials: M
authors.lastname: Mishima
authors.affiliation: Department of Respiratory Care and Sleep Control Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan chink@kuhp.kyoto-u.ac.jp.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Chin
mesh_terms: D015415:Biomarkers / Q000097:blood / Q000378:metabolism; D002248:Carbon Monoxide / Q000097:blood* / Q000378:metabolism*; D045422:Continuous Positive Airway Pressure / Q000379:methods; D045853:Exhalation / Q000502:physiology; D005260:Female; D051547:Heme Oxygenase-1 / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress / Q000502:physiology; D010100:Oxygen / Q000378:metabolism; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012890:Sleep / Q000502:physiology; D020181:Sleep Apnea, Obstructive / Q000097:blood* / Q000378:metabolism / Q000503:physiopathology*
chemical_list: D015415:Biomarkers; D002248:Carbon Monoxide; D051547:Heme Oxygenase-1; D010100:Oxygen
keywords: carbon monoxide; continuous positive airway pressure; heme oxygenase; obstructive sleep apnea