Consequences of hypoxia-reoxygenation phenomena in patients with obstructive sleep apnea syndrome

ABSTRACT

Obstructive sleep apnea syndrome [OSAS] is a common disorder characterized by numerous episodes of absence of respiratory flow during sleep, which can be followed by a decrease in SaO2, which is rapidly normalized when ventilation resumes. We hypothesize that this hypoxia-reoxygenation phenomena may affect the generation of vascular endothelial growth factor [VEGF], erythropoietin [EPO], endothelin-1 [ENDO-1], and inducible nitric oxide synthase [iNOS]. Prospective, patients referred to sleep disorders center. The presence and severity of OSAS were determined using the standard overnight polysomnography. Diagnosis of OSAS was made when the apnea-hypopnea index [AHI] was >/= 15, independent of the appearance of symptoms. Serum levels of VEGF, EPO, ENDO-1, and nitrite-nitrate were measured after overnight fasting in 69 patients with OSAS and in 17 healthy control subjects. Serum levels of VEGF and nitrite-nitrate were measured again after 12 weeks of treatment with continuous positive airway pressure [CPAP] in OSAS patients. Serum VEGF levels were found to be significantly higher and nitrite-nitrate levels were found to be significantly lower in OSAS patients than in controls [P=.003, .008, respectively], but no differences in EPO and ENDO-1 levels were found between the groups. We demonstrated that in OSAS patients, the serum VEGF levels were decreased and nitrate levels were increased after 12 weeks of CPAP treatment [P=.001, .002, respectively]. According to our data, it is likely that hypoxia-reoxygenation phenomena affect the VEGF and nitrite-nitrate levels, which may be pathogenic factors in generating cardiovascular complications in OSAS