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

BACKGROUND AND OBJECTIVES: 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 SaO(2), 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). DESIGN AND SETTING: Prospective, patients referred to sleep disorders center. PATIENTS AND METHODS: 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. RESULTS: 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). CONCLUSION: 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.