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. 2022 Jul 13;128(2):405–417. doi: 10.1152/jn.00469.2021

Figure 1.

Figure 1.

Inspiratory laryngeal drive increases following cervical spinal cord injury. A: endoscopic laryngeal images of a spontaneously breathing, spinally intact cat (isoflurane anesthesia) show abduction (opening) and adduction (closing) of the vocal folds. Muscular attachments (posterior cricoarytenoid and thyroarytenoid) to cartilages in the larynx (arytenoid, cricoid, and thyroid) are illustrated to the right. The vocal folds are white bands of specialized vibratory tissue that are necessary for voice production, and the space between the vocal folds is the glottis. B: laryngeal valving is regulated across the respiratory cycle, with contraction of the posterior cricoarytenoid opening the glottic space during inspiration, and the thyroarytenoid narrowing the glottic space during early expiration (E1). This narrowing increases early-expiratory subglottic pressure and therefore reduces the initial flow of expired gases. Representative traces of electromyogram (EMG) activity recorded from posterior cricoarytenoid (top) and thyroarytenoid (bottom) muscles during eupnea prior to (blue traces) and 90 min after (purple traces) injury. Diaphragm trace (orange) is underlaid on bottom thyroarytenoid panel for reference. There is a substantial increase in laryngeal inspiratory EMG activity after C2 lateral hemisection in cats. Traces are waveform averages of the rectified and smoothed (50 ms) EMGs across 1 min of stable eupneic activity. C: an unrectified raw trace of the posterior cricoarytenoid EMG shows increased inspiratory motor drive immediately following C2 lateral hemisection in spontaneously breathing cats (intravenous pentobarbital anesthesia), that was sustained >90 min after injury. D: the plotted mean integrated posterior cricoarytenoid EMG amplitudes illustrate a significant increase from control (preinjury) in the periods immediately after the injury [t(3) = −5.1, P = 0.02] and 90 min postinjury [t(3) = −6.3, P = 0.008; paired t tests]. There was no significant change in thyroarytenoid EMG amplitude immediately after injury [t(3) = −0.4, P = 0.68] or at 90 min postinjury [t(3) = 1.98, P = 0.19].