Unilateral vocal fold paralysis may result in weak, breathy, and hoarse vocal quality due to glottal incompetence from incomplete glottal closure. The primary goal of surgical intervention is to provide medialization to the involved, paralytic vocal fold allowing its mobile counterpart to make contact during phonation thus improving vocal quality. Medialization thyroplasty, or thyroplasty type I, is one such procedure that was designed to improve glottal closure by inserting a silastic block medial to the paralyzed vocal fold. Currently, there are no standard objective means of assessing changes in glottal competence during medialization thyroplasty. Objective assessment of intra-operative changes in glottal closure that correlate with vocal function would be expected to improve voice outcome.Maximum phonation time (MPT) is an objective measure of vocal function that has been demonstrated to relate to the degree of glottal closure and is sensitive to pre- vs. post-operative medialization thyroplasty results. Normative data on MPT is available with subjects in a standing or seated position. However, medialization thyroplasty is typically performed with the patient in the supine position under conscious sedation or light intravenous anesthesia. Information on the effects of postural changes and/or anesthesia on the ability to maximally sustain sound is not known.The purposes of this investigation were to study the effects of postural positions (supine vs. seated) and anesthesia (light intravenous sedation vs. none) on the measure of MPT. Additionally, the ability of the intra-operative MPT measure to predict the one-month post-surgical value was assessed.Twenty individuals with unilateral vocal fold paralysis undergoing medialization thyroplasty served as subjects in this study. Results indicated that MPT was significantly affected by body position as values were lower in the supine vs. seated position. Secondly, conscious sedation resulted in a trend toward lower MPT values that were not statistically significant. Finally, the intra-operative measure of MPT, while slightly lower than the one-month post-surgical value, was predictive of the outcome. Further research is recommended to determine the critical value of improvement needed in MPT to predict a satisfactory outcome in terms of voice quality and patient satisfaction
