Amis T C, Brancatisano A, Tully A, Engel L A
Thoracic Medicine Unit, Westmead Hospital, New South Wales, Australia.
J Appl Physiol (1985). 1992 Jun;72(6):2329-35. doi: 10.1152/jappl.1992.72.6.2329.
We studied the effects of cricothyroid muscle (CT) contraction on upper airway flow dynamics in eight prone open-mouth anesthetized dogs. Animals were mechanically ventilated via a tracheostomy while a constant airflow (Vuaw) passed through the isolated upper airway. Nasal airflow (Vn) was monitored using a nasal mask and pneumotachograph. Bilateral CT contraction was induced by electrical stimulation of the external branches of the superior laryngeal nerves. During CT contraction with Vuaw of 100-443 ml/s in the inspiratory direction, total upper airway resistance (Ruaw) fell by 49.1 +/- 5.4% (SE) while supraglottic resistance fell by 63.6 +/- 3.6%; simultaneously Vn fell by 55.3 +/- 3.8% and Vuaw increased by 7.2 +/- 1.7%. Similar results were obtained when Vuaw was in the expiratory direction. In three dogs in which the attachments of the CT to either the thyroid or cricoid cartilage were severed, superior laryngeal nerve stimulation had no systematic effect on Ruaw. Because visual assessment during CT contraction consistently revealed dilation of the piriform recesses, we suggest that CT contraction is associated with pharyngeal dilation, which in open-mouth dogs (with overlapping soft palate and epiglottis) redistributes flow to the oral route with a net reduction in Ruaw. Thus the CT may have a respiratory role as a pharyngeal dilator.
我们研究了环甲肌（CT）收缩对八只俯卧位、张口麻醉犬上呼吸道气流动力学的影响。通过气管切开术对动物进行机械通气，同时恒定气流（Vuaw）通过孤立的上呼吸道。使用鼻罩和呼吸速度描记器监测鼻气流（Vn）。通过电刺激喉上神经外支诱导双侧CT收缩。在吸气方向上，当Vuaw为100 - 443 ml/s时，CT收缩期间，上呼吸道总阻力（Ruaw）下降了49.1±5.4%（标准误），而声门上阻力下降了63.6±3.6%；同时，Vn下降了55.3±3.8%，Vuaw增加了7.2±1.7%。当Vuaw在呼气方向时，也获得了类似的结果。在三只CT与甲状腺或环状软骨的附着被切断的犬中，喉上神经刺激对Ruaw没有系统性影响。因为在CT收缩期间的视觉评估一致显示梨状隐窝扩张，我们认为CT收缩与咽部扩张有关，在张口犬（软腭和会厌重叠）中，这会使气流重新分配至口腔途径，同时Ruaw净减少。因此，CT可能作为咽部扩张肌发挥呼吸作用。
