Histologic investigation of hyperphonated canine vocal cords.

Vocal cord injury and its effect on the larynx are topics of considerable importance, yet a clear understanding of acute vocal cord injury from excessive phonation remains elusive. The inability to develop an animal model for vocal abuse has hampered research in this area. This project describes the development of a canine model for acute vocal cord injury from excessive phonation. The method of phonation consisted of a humidified, temperature-controlled, constant flow of air delivered subglottally by an external compressor. A small group of dogs underwent phonation for 2 and 4 hours. Vocal cord injury is described using histologic techniques. Damage to the vocal cords, other than hemorrhage (rare in dogs) and edema, proved to be too elusive for routine microscopy. Scanning and transmission electron microscopy showed extensive surface damage with destruction and loss of the surface microridges and premature desquamation of the vocal cord squamous epithelium. Injury extended to the lamina propria, where the collagen fibers were detached from the basement membrane.