[Glottic measurement and vocal evaluation before and after adult arytenoidectomy].

Objective: To study minimal glottic area which can acquire sufficient airway for decannulation and maximal glottic area which can maintain preoperative vocal function on adult bilateral vocal cord paralysis with unilateral arytenoidectomy.

Methods: Sixteen adult received microscopic right arytenoidectomy with Diomed-25 laser under general anaesthesia and sustained laryngoscope from September 1998 to February 2003. The pre-postoperative glottic measurement and vocal acoustic parameters were analyzed.

Results: The postoperative maximal glottic area, maximal posterior glottic width and maximal opening angle between bilateral vocal cords of the 15 decannulated cases were (45.93 +/- 6.56) mm2, (4.97 +/- 0.73) mm and (24.34 +/- 4.74) degrees respectively. Compared with preoperative period, there were significant difference. Pre-postoperative acoustic parameters (Jitter, Shimmer, harmonics-noise ratio) were analyzed and no significant difference were found (P > 0.05, but there are significant difference in NNE (normalized noise energy) and MPT (maximum phonation time) (P < 0.05). Except for three cases whose postoperative glottic area were more than 50. 1 mm2, there were no significant difference in pre and postoperative NNE (P > 0.05). The minimal glottic area decannulated was 38.0 mm2. The more opening maximal glottic area, the greater of NNE because of bigger closing gap. Noticeable increase of NNE was observed when maximal opening glottic area was up to 50.1 mm2.

Conclusions: The minimal glottic area for decannulation should be 38.0 mm2, and the maximal glottic area for maintaining preoperation vocal function should be 50.1 mm2 on adult bilateral voca cord paralysis with laser aryntenoidectomy.