In Vivo Measures of Vocal Function Responses and Upper Airway Thermoregulation Following Exposure to Varying Environmental Conditions

Abstract

Occupationally-related voice disorders affect a large number of individuals each year, costing the U.S. healthcare system the equivalent in health care dollars spent for the treatment of pediatric ear infections. To date, the influence of upper airway temperature changes on voice function, either passively through environmental temperature manipulations or actively through physical activity, has not been studied. The influences of skeletal muscle tissue temperature change and muscle physiology have been studied extensively in limb skeletal muscles with evidence of thermal effects on muscle biochemistry, contractile function and bioenergetics, yet it is unclear if this research can be translated to the intrinsic laryngeal skeletal muscles. The primary goals of this research were as follows: 1) Determine vocal function differences in five different temperature/relative humidity environments, and 2) Determine vocal function differences following a short bout of submaximal exercise with a targeted respiratory rate of 20 breaths per minute. For both investigations the following measures were taken: phonation threshold pressure, perceived phonatory effort, and pharyngeal temperature. For Aim 1, no significant differences were found for phonation threshold pressure, perceived phonatory effort, or pharyngeal temperature across environments, indicating that the upper airway is tightly regulated for mouth and nose breathing conditions in healthy young adults who were free of any conditions that are currently attributed to the development of voice disorders. For Aim 2, significant increases in phonation threshold pressure and perceived phonatory effort were found with exercise as well as a significant reduction in pharyngeal temperature (1.9°C). The findings support the well-established belief that voice use with physical activity requires greater physical effort. Future investigations should extend these basic models of ambient temperature/relative humidity environments and increased respiratory rate to include volunteers with conditions that are believed to contribute to the development of voice disorder, e.g., reflux, asthma, allergies. Findings from this research may contribute to the development of workplace environmental policy that will promote greater vocal health and reduce the incidence of voice disorders.