Prognostic factors of sleep apnea syndrome : Role of chemosensitivity and dyspnea sensation

阻塞性睡眠呼吸暂停(OSA)因其在睡眠期间反复发作的上呼吸道阻塞而被很好地识别。这些反复出现的气流停止与一过性低氧、高碳酸血症和对阻塞的上呼吸道的吸气努力增加有关。严重阻塞性睡眠呼吸暂停综合征有多脏器并发症，如心血管疾病、肝脏疾病、肾脏疾病和脑部疾病。然而，目前尚不清楚这些患者是否存在呼吸化学控制功能障碍或大脑高级中枢功能障碍。本研究旨在研究阻塞性睡眠呼吸暂停综合征(OSA)患者对低氧、高碳酸血症的呼吸反应和增加吸气阻力负荷时的吸气用力感觉(IES)，以及鼻腔持续正压(CPAP)对这些参数的影响。鼻式CPAP后，低氧呼吸反应明显降低，而高二氧化碳呼吸反应明显增加。阻塞性睡眠呼吸暂停综合征患者的吸气阻力负荷低于对照组。鼻塞式CPAP治疗后IES恢复到正常水平，提示OSA患者对低氧、高碳酸血症和白天增加吸气负荷的IES反应异常，鼻塞式CPAP治疗可以改善OSA患者的这些反应。OSA的化疗敏感性改变和脑高级中枢功能低下可能影响OSA的严重程度。

Obstructive sleep apnea(OSA) is well recognized by its repeated episodes of upper airway obstruction during sleep. These recurrent cessation of airflow are associated with transient episodes of hypoxia, hypercapnia, and increasing inspiratory effort against the obstructed upper airway. Severe OSA has multiorgan complications such as caridiovascular diseases, liver diseases, renal diseases and cerebral diseases. However, it has not been clarified whether these patients have dysfunction of chemical control of breathing or higher brain center. In the present study, we aimed to study the ventilatory responses to hypoxia and hypercapnia and the inspiratory effort sensation(IES) to added inspiratory resistive loading, and to study the effect of nasal continuous positive airway pressure(CPAP) on these parameters in patients with OSA.The ventilatory response to hypoxia was higher and the ventilatory response to hypercapnia was lower than normal response of our laboratory before nasal CPAP. After nasal CPAP, the ventilatory response to hypoxia significantly decreased, whereas the ventilatory responses to hypercapnia significantly increased. IES to inspiratory resistive loading was lower in patients with OSA than in control subjects. After nasal CPAP, the IES increased to normal level.The results suggest that patients with OSA have the abnormal ventilatory responses to hypoxia, hypercapnia and IES response to added inspiratory loading during the daytime, and that nasal CPAP treatment can improve these responses in OSA. The altered chemosensitivity and lowered function of higher brain center may affect the severity of OSA.