title: Thyroid cartilage movements during breathing.
abstract: We measured lateral (outward) thyroid cartilage displacement (TCD) of the larynx in six supine anesthetized (intravenous chloralose) dogs. Combined left and right TCDs were measured with linear transducers attached by a thread to the thyroid alae. During tidal breathing via a tracheostomy, phasic inspiratory TCD occurred in all dogs [0.66 +/- 0.2 mm (mean +/- SE)] together with phasic inspiratory electromyographic activity in the cricothyroid (CT) and posterior cricoarytenoid (PCA) muscles. During brief tracheal occlusions, TCD increased significantly to 1.27 +/- 0.2 mm (P = 0.001), accompanied by an increase of 95-115% in the peak CT and PCA electromyograms. Bilateral supramaximal electrical stimulation of the external branches of the superior laryngeal nerve (ExSLN) produced a TCD of 9.9 +/- 0.8 mm; however, similar stimulation of the recurrent laryngeal nerve (RLN) produced a TCD of only 1.33 +/- 0.1 mm (P = 0.0001). Furthermore, bilateral section of the ExSLN in five dogs significantly reduced tidal TCD by 48.7 +/- 24.4% (P < 0.05), and bilateral section of both the ExSLN and RLN resulted in slight phasic inward TCD (-0.06 +/- 0.05 mm). Thus, it appears that the activities of both the CT and RLN-innervated muscles (probably the PCA muscle) contribute to tidal breathing TCD. These findings suggest that inspiratory dilation of the hypopharynx is mediated by contractions of CT and PCA muscles.
authors.affiliation: Department of Respiratory Medicine, Westmead Hospital, New South Wales, Australia.
authors.forename: T C
authors.initials: TC
authors.lastname: Amis
authors.forename: A
authors.initials: A
authors.lastname: Brancatisano
authors.forename: A
authors.initials: A
authors.lastname: Tully
mesh_terms: D000758:Anesthesia; D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D004576:Electromyography; D007821:Laryngeal Muscles / Q000502:physiology; D007823:Laryngeal Nerves / Q000502:physiology; D007830:Larynx / Q000033:anatomy & histology / Q000502:physiology; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000502:physiology*; D013909:Thorax / Q000502:physiology; D013957:Thyroid Cartilage / Q000033:anatomy & histology / Q000502:physiology*; D014132:Trachea / Q000502:physiology; D014160:Transducers, Pressure