Contraction Patterns of Intrinsic Laryngeal Muscles Induced by Orderly Recruitment in the Canine

Abstract

The specific performance of intrinsic laryngeal muscles has been difficult to evaluate, especially in living subjects. To reproduce natural contractions, we artificially induced orderly recruitment of their innervating axons according to the size principle. In 5 dogs, both recurrent laryngeal nerves (RLNs) were stimulated with 50 through 10 Hz, 300 to 1000 microA currents while 600 Hz, 1000 to 0 microA decreasing blocking currents were administered. Surface electromyography electrodes placed on the thyroarytenoid, posterior cricoarytenoid, and lateral cricoarytenoid muscles were used to determine the amplitudes (in mA) of compound muscle action potentials. There was a highly statistically significant difference (P<.004) between the thyroarytenoideus which had the fastest rate of recruitment (8.38%), and posterior cricoarytenoideus, which had the slowest (4.81%). There was an intermediate recruitment rate (6.72%) of the lateral cricoarytenoideus, a divergence attributed to a more equal distribution in fast and slow types of myofibers and a smaller sample. We submit that RLN axons can be recruited in an orderly manner according to their sizes and that the rates are unique to the muscle classes they innervate. The parameters defining these contraction patterns may offer key information for laryngeal pacing.

Artificial Control of Glottic Adduction for Aspiration by Orderly Recruitment in the Canine

“…Preliminary data have shown that intrinsic laryngeal muscles could be distinguished according to their dominant motor units architectures [10]. Progression rates of compound muscle action potentials were unique to each muscle class under study (TA, CT, LCA, and PCA) (Fig.…”

“…This work continues a pilot study in which the contractile capabilities of various intrinsic laryngeal muscles were defined according to their specific responses to orderly stimulation [10]. We propose that this information should be potentially used to control glottic closure, when clinically indicated for swallowing disorders.…”

“…In order to reproduce naturally occurring contractions of the intrinsic laryngeal muscles [9,10], we used a circuit pioneered by Zhou et al [11] and Barrata et al [12] in feline sciatic nerve-hindlimb preparations. The superior and recurrent laryngeal nerves carry the information responsible for closing the glottic chink.…”

Electronic Analysis of Intrinsic Laryngeal Muscles in Canine Sound Production

“…By adherence to statistical assumptions of the tests performed and use of Bonferroni adjusted p values to examine the significance of multiple testings, this number of animals was set to detect whether independent variables accounted for 20% of the variability of the response variable with at least 90% power, as based on results of a previous study. 12 After intravenous anesthesia with pentobarbital sodium, halothane and oxygen were administered through an endotracheal tube in the supine animals ( Fig I). Through a midline cervical incision, the dogs' artificial airways were converted to a low tracheostomy with the distal aspect of the tube facing downward well above the carina for effective bilateral pulmonary ventilation.…”

“…In addition, a 30 gauge platinum wire was looped around both SLNs. Pairs of spherical surface EMG electrodes (N = 3) similar to those used in a previous study 12 were placed to effect direct contact over each of the 3 muscles (TA, PCA, CT; Fig 2). The stimulation module of the circuit (Biomedical Corporation of America, Cleveland, Ohio) produced 10 to 100 Hz, 0 to 7,000 /-lA, 0 to 1,000 ms currents with a 600 Hz, 7,000 to 0 /-lA blocking envelope injected into the RLNs and vagus nerves.…”