Kondo Eiji, Jinnouchi Osamu, Ohnishi Hiroki, Kawata Ikuji, Takeda Noriaki
Nihon Jibiinkoka Gakkai Kaiho. 2015 Nov;118(11):1319-26. doi: 10.3950/jibiinkoka.118.1319.
Cough and swallowing reflexes are important airway-protective mechanisms against aspiration. Angiotensin-converting enzyme (ACE) inhibitors, one of the side effects of which is cough, have been reported to reduce the incidence of aspiration pneumonia in hypertensive patients with stroke. ACE inhibitors have also been reported to improve the swallowing function in post-stroke patients. On the other hand, stimulation of the Arnold nerve, the auricular branch of the vagus, triggers the cough reflex (Arnold's ear-cough reflex). Capsaicin, an agonist of Transient Receptor Potential Vanilloid 1 (TRPV1), has been shown to activate the peripheral sensory C-fibers. Stimulation of the sensory branches of the vagus in the laryngotracheal mucosa with capsaicin induces the cough reflex and has been reported to improve the swallowing function in patients with dysphagia. In our previous study, we showed that aural stimulation of the Arnold nerve with 0.025% capsaicin ointment improved the swallowing function, as evaluated by the endoscopic swallowing score, in 26 patients with dysphagia. In the present study, the video images of swallowing recorded in the previous study were re-evaluated using the SMRC scale by an independent otolaryngologist who was blinded to the information about the patients and the endoscopic swallowing score. The SMRC scale is used to evaluate four aspects of the swallowing function: 1) Sensory: the initiation of the swallowing reflex as assessed by the white-out timing; 2) Motion: the ability to hold blue-dyed water in the oral cavity and induce laryngeal elevation; 3) Reflex: glottal closure and the cough reflex induced by touching the epiglottis or arytenoid with the endoscope; 4) Clearance: pharyngeal clearance of the blue-dyed water after swallowing. Accordingly, we demonstrated that a single application of capsaicin ointment to the external auditory canal of patients with dysphagia significantly improved the R, but not the S, M or C scores, and this effect lasted for 60 min. After repeated aural stimulation with the ointment for 7 days, the R score improved significantly in patients with severe dysphagia. The present findings suggest that stimulation of the Arnold's branch of the vagus in the external auditory canal with capsaicin improves the glottal closure and cough reflex in patients with dysphagia. Thus, aural stimulation with capsaicin represents a novel treatment for dysphagia. It is also suggested that repeated alternative aural stimulation with capsaicin for a week, rather than a single application, is needed to improve the swallowing function in patients with severe dysphagia. By the same mechanism as that underlying the effect of ACE inhibitors, aural stimulation with capsaicin may reduce the incidence of aspiration pneumonia in patients with dysphagia.
咳嗽和吞咽反射是防止误吸的重要气道保护机制。血管紧张素转换酶（ACE）抑制剂的副作用之一是咳嗽，据报道，它可降低中风后高血压患者误吸性肺炎的发生率。据报道，ACE抑制剂还可改善中风后患者的吞咽功能。另一方面，刺激阿诺德神经（迷走神经的耳支）会引发咳嗽反射（阿诺德耳咳反射）。辣椒素是瞬时受体电位香草酸亚型1（TRPV1）的激动剂，已被证明可激活外周感觉C纤维。用辣椒素刺激喉气管黏膜中的迷走神经感觉支可诱发咳嗽反射，据报道，这可改善吞咽困难患者的吞咽功能。在我们之前的研究中，我们发现，用0.025%辣椒素软膏对外耳道进行阿诺德神经耳内刺激，可改善26例吞咽困难患者的吞咽功能，这一功能通过内镜吞咽评分进行评估。在本研究中，由一名对患者信息和内镜吞咽评分不知情的独立耳鼻喉科医生，使用SMRC量表对之前研究中记录的吞咽视频图像进行重新评估。SMRC量表用于评估吞咽功能的四个方面：1）感觉：通过变白时间评估吞咽反射的启动；2）运动：在口腔中含住蓝色染色水并诱发喉部抬高的能力；3）反射：声门关闭以及用内镜触碰会厌或杓状软骨诱发的咳嗽反射；4）清除：吞咽后咽部对蓝色染色水的清除。因此，我们证明，对吞咽困难患者的外耳道单次涂抹辣椒素软膏可显著改善R评分，但对S、M或C评分无改善，且这种效果持续60分钟。用该软膏反复进行耳内刺激7天后，重度吞咽困难患者的R评分显著改善。本研究结果表明，用辣椒素刺激外耳道中的迷走神经阿诺德支可改善吞咽困难患者的声门关闭和咳嗽反射。因此，辣椒素耳内刺激是一种治疗吞咽困难的新方法。还表明，对于重度吞咽困难患者，需要用辣椒素反复交替进行耳内刺激一周，而不是单次涂抹，以改善其吞咽功能。通过与ACE抑制剂作用相同的机制，辣椒素耳内刺激可能会降低吞咽困难患者误吸性肺炎的发生率。
