LXXI Physiological Studies of the Replanted Canine Larynx

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Abstract
The effect of laryngeal vessel interruption on muscular action potential of the larynx and the influence of nerve excision on the local blood circulation is studied. The measurement of the cranial thyroid artery averages 2.5 mm in diameter while that of the laryngeal artery is 0.5 mm. The blood flow volume through the larynx averages 6.7 c/min. The flow volume passing through the laryngeal artery is 30 to 40% of the total blood flow volume through the larynx, while that of the cranial thyroid artery is 50 to 60%. However, unilateral laryngeal or unilateral cranial thyroid artery proved to be sufficient blood supply for the survival of a transplanted larynx. Following the alterations of the blood flow volume through the larynx, electromyo-graphic variations of the laryngeal muscle were delayed. The laryngeal nerves are unmistakably necessary to maintain normal blood circulation of the larynx since denervation causes a reduced blood flow volume through the larynx. The stimulation frequency of 15 times per second to the recurrent nerve promoted optimum blood flow volume through the larynx but a stimulation of over 15 times per second in frequency, depressed the flow volume through the larynx. Although the laryngeal artery is very small, its blood supply is as important as the cranial thyroid artery in maintaining the viability of the larynx and necessarily the survival of the larynx. With the utilization of pre-operative excision of the laryngeal artery, resistance of the laryngeal muscle to local ischemia is increased. Complete interruption of the laryngeal vessels caused a reduction and disappearance within 30 nun. of the amplitude of action potential on the intrinsic laryngeal muscles. The perfusion of Dextran is not as effective in maintaining laryngeal viability as oxygenated blood, as shown by electromyographic measurement.

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