Use of the phonation analyzer as a clinical tool

Isshiki's (1981) proposed index of glottal flow efficiency (ac/dc ratio) and an instrument designed to measure the index (PA 500) were evaluated. Measurements of glottal flow, SPL, and fundamental frequency obtained from the PA 500 were compared with measurements obtained from more established laboratory instruments and found to be similar. Then the PA 500 was used to obtain measurements from 50 subjects without voice disorders or laryngeal pathology, 14 subjects with voice disorders and no laryngeal pathology, and 41 subjects with voice disorders and laryngeal pathology. Comparisons of ac/dc ratios revealed some significant differences among subject groups. However, when Isshiki's proposed cutoff ratio (ac/dc = 0.50) was used to determine which subjects had laryngeal pathology, 33% of the 105 subjects were misidentified. Data collected in the study provided an opportunity to evaluate Hirano's (1981) suggestion that glottal flow rates of 200 cc/s may be considered abnormal. When this flow rate was used as a cutoff score to determine which subjects had laryngeal pathology, 24% of the 105 subjects were misidentified. High variability in measurements obtained from subjects in each of the groups studied suggest that it is unlikely that ac/dc ratios or glottal flow measures, by themselves, will prove to be effective in identifying subjects with laryngeal pathology.