title: Characteristics of glottic closure reflex in a canine model.
abstract: OBJECTIVE
  The most important function of the larynx is airway protection which is provided through a polysynaptic reflex closure triggered by the receptors in the glottic and supraglottic mucosa, evoking the reflex contraction of the laryngeal muscles especially by strong adduction of vocal cords. Based on the hypotheses that central facilitation is essential for this bilateral adductor reflex and that its disturbance can result in weakened laryngeal closure, we designed this study to elucidate the effect of central facilitation on this protective reflex.
  
  
  METHODS
  Seven adult, 20 kg mongrel dogs underwent evoked response laryngeal electromyography under 0.5 to 1.0 MAC (minimum alveolar concentration) isoflurane anesthesia. The internal branch of the superior laryngeal nerve was stimulated through bipolar platinum-iridium electrodes, and recording electrodes were positioned in the ipsilateral and contralateral thyroarytenoid muscles.
  
  
  RESULTS
  Ipsilateral reflex closure was consistently recorded regardless of anesthetic levels. However, contralateral reflex responses disappeared as anesthetic levels were deepened. Additionally, late responses (R2) were detected in one animal at lower level of anesthesia.
  
  
  CONCLUSIONS
  Deepened level of anesthesia affects central facilitation and results in the loss of the crossed adductor reflex, predisposing to a weakened glottic closure response. Precise understanding of this effect may possibly provide a way to prevent aspiration in unconscious patients.
authors: Department of Otorhinolaryngology, Yonsei University College of Medicine, 250 Seongsan-ro, Seodaemun-gu, Seoul, Korea. yhkimmd@yuhs.ac
authors: Young-Ho
authors: YH
authors: Kim
authors: Ju Wan
authors: JW
authors: Kang
authors: Kwang-Moon
authors: KM
authors: Kim
mesh_terms: D000758:Anesthesia / Q000379:methods; D000818:Animals; D004285:Dogs; D005931:Glottis / Q000502:physiology*; D007823:Laryngeal Nerves / Q000502:physiology; D012018:Reflex