Study of cerebrovascular reserve capacity in obstructive sleep apnea-hypopnea syndrome

Abstract

Objective To assess cerebrovascular reserve capacity in patients with obstructive sleep apnea-hypopnea syndrome(OSAHS).Methods One hundred and fourteen patients with OSAHS and 43 normal persons were enrolled in this study.The patients were divided into mild,moderate,severe according to apnea hypopnea index (AHI) and LSaO2 (lowest arterial oxygen saturation).All the patients and normal persons were routinely examined using transcranial Doppler (TCD) and end-tidal carbon dioxide partial pressure(ETCO2) to evaluate cerebrovascular reserve.Hypercapnia was induced by inhaling the CO2 which produced by the patients themselves,and hypocapnia was elicited by voluntary hyperventilation.Results CVR in the severe and moderate OSAHS were significantly lower than that in the control group [ (1.80 ± 1.34) ％/mm Hg and (1.43 ±1.05)％/mm Hg vs (2.93 ±0.93)％/mm Hg,P ＜0.05] when patients in the condition of hypocapnia.And there was no significant difference on CRV between the mild OSAHS group and control group [ (2.53 ±1.83 ) ％/mm Hg vs ( 2.93 ± 0.93 ) ％/mm Hg,P ＞ 0.05 ].When patients in the condition of Hypercapnia,CRV in the severe and moderate OSAHS were also significantly lower than that in the control group [ ( 1.83 ±1.32) ％/mm Hg and (1.08 ± 1.00)％/mm Hg vs (3.32 ± 1.53)％/mm Hg,P ＜ 0.05),AHI was negatively correlated with the cerebrovascular reserve at the condition of hypercapnia and hypocapnia (r=-0.665,-0.721; P ＜ 0.05 ).Conclusion Inhaling CO2 is a effective method for assessing CVR.Cerebrovascular reserve capacity is associated with AHI.Reduced CVR causes hemodynamics change being severe hypoxia in the moderate and severe OSAHS. Key words: Obstructive sleep apnea-hypopnea syndrome; Cerebrovascular reserve capacity; Transcranial Doppler ultrasonography; Inhaling CO2