In Vivo Measures of Vocal Function Response to Environmental Conditions

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DESCRIPTION (provided by applicant): There is little scientific evidence to support commonly used clinical treatment strategies for voice disorders. Clinicians routinely recommend increased ambient humidity, proper hydration, and avoidance of dry or thermally challenging environments, strategies that are believed to promote best vocal function and perception of vocal ease. However, there is not a good understanding of how environmental parameters, specifically the interdependence of ambient temperature, humidity, and vapor pressure affect the voice. Due to the interdependence of these variables, it is difficult to investigate a single environmental factor (e.g., humidity) when studying laryngeal tissue functions. The interrelatedness of temperature, vapor pressure, and humidity has not been systematically studied in prior investigations of voice function. The interdisciplinary design of the proposed research will investigate the influence of ambient temperature and vapor pressure, which collectively influence relative humidity, on vocal function. This novel application of concurrent measures of laryngeal environment temperature (pharyngeal thermister temperature probe and infrared thermal imaging) with clinical measures of vocal function (phonation threshold pressure and perceived vocal effort) allows for systematic study of the effect of environmental conditions and increased ventilation rate on vocal tissue function. The hypothesis of this study is that alterations in ambient conditions (temperature, vapor pressure, humidity) are associated with increased pressure thresholds (phonation threshold pressure) for phonatory onset and increased perception of effort when compared with a thermally neutral condition. This work has two specific aims: 1) To determine if changes in ambient temperature, vapor pressure, and humidity influence phonatory onset, regional laryngeal temperature, and perception of vocal ease for mouth versus nose inhalation using a within-subject repeated measures design. This may influence airway humidity and tissue moisture content. 2) To determine if increased ventilation rate (convective airflow within laryngeal region) induced by submaximal aerobic exercise influences regional laryngeal temperature and efficiency of phonatory onset differently than resting nasal breathing using a within-subject repeated measures design. Given the anatomical and physiological challenges of accessing the laryngeal tissues, measurements of the laryngeal thermal environment and vocal fold tissue function under varying ambient environmental conditions will contribute to our understanding of voice use in cold and warm environments that differ from the neutral environmental conditions of the typical clinic setting. This work will elucidate the environmental demands placed on the laryngeal tissue and provide evidence to guide clinical voice rehabilitation and habilitation of effective, safe voice use under realistic environmental conditions. PUBLIC HEALTH RELEVANCE: Published research indicates that the relative humidity of the air we breathe may influence how easily we use our voice; however, we do not yet understand the interdependent relationship of environmental temperature and humidity on tissues within the voice box (larynx). This relationship may be dependent upon the air vapor pressure (point at which air condenses or evaporates), which is a crucial component of our understanding of how the larynx adjusts the moisture of the vocal tissues in health and disease. Accounting for environmental impact on the muscles and tissues of the voice box may help us understand how to best train or rehabilitate the voice for work that requires extensive voice use or voice use in extreme temperature environments.