Exploring the Relation between Glottal Closure and Plasma Substance P: A Study Protocol.

Glottal incompetence, i.e., reduced ability to produce effective glottal closure, is a problem often associated with aging. The study protocol is presented to determine whether blood substance P (SP) serves as an indicator of glottal closure function among the elderly. SP is involved in the neuromuscular mechanisms of cough; reduced concentration of SP may be a marker for increased risk of aspiration pneumonia. The antihypertensive angiotensin-converting enzyme inhibitor, which also inhibits degradation of SP, has been found to be effective in preventing aspiration pneumonia by strengthening the cough reflex. In this study, we will employ National Hospital Organization self-controlled vocal exercise (NHOEx), which has been shown to improve glottal closure by strengthening the laryngeal adduction muscles. We hypothesize that improved glottal closure by NHOEx may lead to the increase in the plasma concentration of SP, which reflects effective cough reflex. Maximum phonation time (MPT), an indicator of glottal closure, will be measured to assess improvement of glottis-closing function. The study will include 180 patients over 65 years old with dysphonia, dysphagia, or MPT of less than 15 seconds. Based on the speculation that the improved MPT may be associated with changes in SP expression, we will measure the plasma SP before and after 6-month treatment of glottal incompetence using NHOEx. The goal is to verify the reliability of SP as an indicator for glottal closure and swallowing function. Measurement of plasma SP may be helpful for earlier detection of subjects with higher risk of aspiration pneumonia among the elderly.