Circulating carbon monoxide level is elevated after sleep in patients with obstructive sleep apnea.
BACKGROUND
Patients with obstructive sleep apnea (OSA) have an increased risk of cardiovascular morbidity. This study aimed to determine circulating carbon monoxide (CO) levels, which have been suggested to be a marker of cardiovascular risk in patients with OSA.


METHODS
Venous blood samples were obtained from 35 patients with OSA and 17 age-matched, healthy control subjects before and after polysomnography. Concentrations of venous CO and serum heme oxygenase (HO)-1 were determined by gas chromatography and enzyme-linked immunosorbent assay, respectively.


RESULTS
Circulating CO levels in OSA patients were significantly increased in the morning, but not in the evening. The change in CO level, which was defined as a gap between the presleep and postsleep CO levels, correlated with apnea-hypopnea index and hypoxia duration as a percentage of total sleep time. No difference was found in serum HO-1 levels between OSA patients and control subjects. Treatment with continuous positive airway pressure (CPAP) resulted in normalization of the postsleep CO level.


CONCLUSIONS
The postsleep circulating CO level is helpful for assessing the clinical severity of OSA. Moreover, treatment of OSA with CPAP can potentially reduce the risk of the disease associated cardiovascular events.
Kobayashi
Masayoshi
M
Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
Miyazawa
Naoki
N
Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
Takeno
Mitsuhiro
M
Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
Murakami
Shuji
S
Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
Kirino
Yohei
Y
Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
Okouchi
Akiko
A
Department of Internal Medicine, Yokohama Seamen's Insurance Hospital, Yokohama, Japan.
Kaneko
Takeshi
T
Respiratory Center, Yokohama City University Medical Center, Yokohama, Japan.
Ishigatsubo
Yoshiaki
Y
Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, Yokohama, Japan. Electronic address: ishigats@med.yokohama-cu.ac.jp.
D002248:Carbon Monoxide / Q000097:blood*; D002318:Cardiovascular Diseases / Q000097:blood / Q000209:etiology; D002849:Chromatography, Gas; D045422:Continuous Positive Airway Pressure / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D051547:Heme Oxygenase-1 / Q000097:blood; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D011379:Prognosis; D012307:Risk Factors; D012890:Sleep / Q000502:physiology*; D020181:Sleep Apnea, Obstructive / Q000097:blood* / Q000503:physiopathology / Q000628:therapy
D002248:Carbon Monoxide; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1