Am. J. Respir. Crit. Care Med., Vol 155, No. 2, Feb 1997, 637-641.
Activation of intrinsic laryngeal muscles during cough
G Sant'Ambrogio, ST Kuna, CR Vanoye and FB Sant'Ambrogio
Department of Physiology, University of Texas Medical Branch, Galveston 77555-0641, USA.
We studied the pattern of discharge of the posterior cricoarytenoid (PCA),
cricothyroid (CT), thyroarytenoid (TA), and arytenoideus transversus (AR)
muscles during cough in 12 anesthetized dogs. Diaphragm electromyographic
(EMG) activity was also recorded, together with subglottic and esophageal
pressures. Trains of repetitive coughs were induced by mechanically
stimulating the tracheobronchial airway. Trials with the upper airway
isolated from and connected to the lower airway were performed before and
following bilateral sectioning of the internal branch of the superior
laryngeal nerve (SLN). The immediate effect of tracheal stimulation was an
"apneic" period at FRC, during which the PCA, a laryngeal abductor, showed
a progressive increase in activity accompanied by small, variable increases
in the activity of the CT and the laryngeal adductors, the TA and AR. The
subsequent cough efforts were divided into three phases: inspiration,
glottic narrowing, and forced expiration. PCA activity was greatest during
the inspiratory phase and CT activity was greatest during the expiratory
phase. Peak subglottic pressure occurred during glottic narrowing and
coincided with the greatest activation of the TA and AR during the cough
effort, and suppression of the PCA and CT. The patterns of EMG activation
were not affected by the route of breathing or SLN section. The results
suggest the presence of a uniquely central process controlling laryngeal
muscles during cough, independent of laryngeal sensory feedback.
