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

阻塞性睡眠呼吸暂停（OSA）因其在睡眠中反复发作的上呼吸道阻塞而被公认。这些反复的气流停止与短暂性缺氧、高碳酸血症发作和对阻塞的上呼吸道吸气力增加有关。严重的OSA有多器官并发症，如心血管疾病、肝脏疾病、肾脏疾病和大脑疾病。然而，尚不清楚这些患者是否存在呼吸化学控制功能障碍或高级脑中枢功能障碍。在本研究中，我们旨在研究OSA患者对低氧和高碳酸血症的通气反应以及吸气用力感（IES）对吸气阻力负荷的增加，并研究鼻腔持续气道正压通气（CPAP）对这些参数的影响。低氧通气反应较高，高碳酸血症通气反应较实验室正常通气反应低。经鼻CPAP治疗后，低氧通气反应明显降低，高碳酸血症通气反应明显增加。OSA患者吸入阻力负荷的IES低于对照组。经鼻CPAP后，IES恢复正常。结果提示，OSA患者在白天对低氧、高碳酸血症和增加吸气负荷有异常的通气反应，鼻腔CPAP治疗可以改善OSA患者的这些反应。化疗敏感性的改变和高脑中枢功能的降低可能影响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.