From the Department of Surgery, Division of Otolaryngology Head and Neck Surgery (j.a.r., n.p.c.), University of Wisconsin, Madison, Wisconsin, U.S.A.; the Department of Otolaryngology Head and Neck Surgery (h.n.), Kitasato University School of Medicine, Kanagawa, Japan; and the Department of Communicative Disorders (n.p.c.), University of Wisconsin, Madison, Wisconsin, U.S.A.
OBJECTIVE/HYPOTHESIS:: Age-associated muscular changes and fatigue have been shown to affect phonatory function. Reductions in blood flow with aging could translate to reductions in oxidative capacity within laryngeal muscles and increased fatigability. We tested the hypothesis that there would be increased capillary red blood cell (RBC) velocity and a reduction of capillary density in the thyroarytenoid (TA) muscle of senescent rats. STUDY DESIGN/METHODS:: Ten male Fisher 344/Brown Norway rats in two age groups were used: young adult (9 mo) and old (28-30 mo). Sixteen additional young and old rats were used in a fluorescent microsphere experiment that examined blood flow rates before and after a surgical manipulation. With use of a specially equipped intravital microscope, in vivo measurements of capillary geometry and flow were obtained, including RBC velocity, capillary density, tortuosity, and number of branch points. RESULTS:: There was an age-related reduction in capillary surface area as evidenced by reduced lineal density of capillaries. In addition, reduced RBC transit time was suggested by the reduction in branch points found with age. There was no change in RBC velocity with aging. The surgical method used to expose the TA muscle for blood flow recordings did not significantly affect resultant blood flow measurements. CONCLUSIONS:: We developed a method to evaluate in vivo laryngeal microvasculature. We found age-related changes in microvascular geometry within the TA muscle of the rat that could affect blood flow to this critical muscle of phonation and airway protection. These micro vascular changes could contribute to age-related laryngeal dysfunction.