Clinical Evaluation of Air Usage during Phonation

For measuring air usage during phonation, we recorded the air volume curve as a function of time during sustained phonation by using a spirometer coupled with a simple electrical device. As an indirect estimation of air usage, the phonation quotient (PQ) was also calculated from the vital capacity (VC) and the maximum phonation time (MPT) ; PQ=VC/MPT. This paper reports on a comparative study of PQ and the mean flow rate obtained by the spirometer. The subjects were 50 normal adults ; 25 male and 25 female, and 180 pathological cases ; 75 male and 105 female. For each subject, the mean flow rate was obtained by the spirometer under two different phonatory conditions ; maximum sustained phonation after maximum inspiration and easy sustained (3 to 5 sec) phonation after normal breathing. Comparison of the three values revealed that the mean flow rate during maximum sustained phonation showed a high degree of positive correlation with that of easy phonation as well as with PQ. On the other hand, a lesser degree of positive correlation was found between the mean flow rate during easy sustained phonation and PQ. It was also concluded that the mean flow rate during easy sustained phonation, which was considered to best represent the phonatory condition in daily life, was the most sensitive among the three values for detecting abnormality in air usage. It was further concluded that these measurements were valuable for the gross evaluation of air usage during Phonation.