Aerodynamic evaluation of the postthyroidectomy voice.

OBJECTIVES/HYPOTHESES: Changes in vocal function before and after thyroidectomy were examined using aerodynamic and related assessments. Laryngeal airway resistance (R(law)) and phonation threshold pressure (PTP) were hypothesized to be sensitive to changes in laryngeal function that may occur after thyroidectomy separate from changes that may occur from endotracheal intubation alone.

STUDY DESIGN

Prospective longitudinal clinical trial with comparison group.

METHODS

Eighty patients were evaluated preoperatively, and 2 weeks and 3 months postoperatively to assess voice outcomes after thyroidectomy. In addition, 16 patients who underwent a nonneck operation were tested as a control group. Maximum phonation time (MPT), mean airflow, R(law), and PTP were determined at two vocal fundamental frequency (F0) levels (30% and 80% of the F0 range).

RESULTS

No systematic differences were detected for MPT, mean airflow, or R(law) as a short-term or intermediate-term outcome of either surgical group. PTP decreased significantly over time for both groups of participants and at both F0 levels. F0 range decreased significantly at the short-term postsurgical assessment and covaried with the PTP results, thereby explaining some of the variability in the PTP data.

CONCLUSIONS

Aerodynamic assessment did not reveal systematic changes in vocal function associated with thyroidectomy, although PTP decreased postoperatively for both surgical groups. This may be attributable in part to a learning effect or to postoperative reductions in F0 range.