Abstract
Movements of the vocal cord (s) and biomechanic findings of the glottis induced by a stimulation of each nerve branch to the intrinsic laryngeal muscles at a constant intencity of 1 volt with increasing frequency were investigated in 68 dogs.
1. Shape of the glottis The vocal cord became longer and slightly adducted by a stimulation of bilateral external branches at 30 to 40 Hz. It abducted most widely by a stimulation of the posticus branch at the same frequency, while it adducted most strongly when each branch to the vocalis, lateralis and transversus muscles was stimulated at 60 Hz.
2. Width of the glottic chink The glottic chink became narrowest by a stimulation of bilateral external branches at 35 to 40 Hz. It became widest by a stimulation of bilateral posticus branches at the same frequency, while the narrowest glottic chink was obtained by a stimulation of each branch to the adductors at 60 Hz.
3. Glottic pressure The glottic pressure showed 395 mmH20 when bilateral external branches were stimulated at 40 to 45 Hz. It reached high up to 550, 570 and 290 mmH20 by a stimulation of the nerves to vocalis at 95 to 100 Hz, lateralis at 85 to 95 Hz and transversus at 95 to 100 Hz.
4. Tension of adduction or abduction in the horizontal plane
The strongest tension was obtained by a stimulation of the external branch at 40 Hz and it measured 11.2 gr, while it reached 16, 11.4 and 5 grs by a stimulation of nerve branches to lateralis at 85 Hz, vocalis at 80 Hz and transversus at 60 Hz respectively.
Wider glottic chink, higher glottic pressure and stronger tension of the vocal cord could not be obtained by a stimulation of any nerve branch with higher frequency than those mentioned above.
