Estimating vocal fold stiffness: Using the relationship between subglottic pressure and fundamental frequency of phonation as an analog.

OBJECTIVE

The stiffness of the vocal folds is an important factor in voice production, yet clinically applicable measurements are still lacking. It has been demonstrated in an in vivo canine model that fundamental frequency (F ) increased linearly as subglottic pressure (P ) increased, but with a lesser slope for higher levels of vocal fold tension. In this study, the relationship between F and P was investigated using the airflow interruption method in awake patients non-invasively.

DESIGN

Healthy volunteers enrolled for evaluation.

SETTING

Single-centre.

PARTICIPANTS

Thirty-three healthy volunteers aged 20 and older were recruited, with one excluded for a recent asthma attack.

MAIN OUTCOME MEASURES

The relationships between F and P , described as the slope (Hz/kPa), were investigated when the participants sustained voicing the vowel/o/at 3 incremental frequencies 4 semitones apart in the modal register (F1, F2 and F3).

RESULTS

Thirty-two healthy volunteers (20 females, 12 males) aged 20-47 years were enrolled for final analyses. There was a statistically significant difference in the slopes of the linear regression lines of F -P , depending on the frequency with which the vowel/o/ was produced (P < .001). The slope differed significantly between F2 and F1 (P < .001; P = .015), F3 and F1 (P < .001; P = .002) and F3 and F2 (P < .001; P = .005) for both women and men, respectively.

CONCLUSIONS

It was demonstrated that the higher the vocal fold tension, the smaller the slope between F and P . Using the relationship between F and P as an analog of vocal fold stiffness is potentially practical for clinical application.