抄録
Tracheal fenestration is more profitable than tracheotomy in patients who need tracheostoma open for a long period. After tracheal fenestration has been done, the patient does not need to have a tracheal canula in the tracheostoma, and principally, he can phonate without closing the tracheostoma with the finger.
The purposes of the present investigation comprise 1) to determine the technique best in a phonic aspect, and 2) to establish a simpler procedure than the Rockey's original one, which is rather complicated and accompanied by large scar formation on the neck. Phonic function was studied in five cases who had received tracheal fenestration. Subglottic pressure was registered with excised canine larynges coupled to a simulated bronchial tree system. The results are summarized as follows:
1. When the excised larynges were blown, the subglottic pressure varied rapidly corresponding to the vocal cord vibration. The variation of the pressure was greatest in size immediately below the vocal cords, becoming less as the distance from the glottis became greater in the trachea. No oscillation of the pressure was found below the carina.
2. The size of the oscillation of the subglottic pressure was proportional to the intensity of phonation. This suggests that the air below the glottis is compressed during phonation. The change in size of pressure oscillation on the basis of the intensity of phonation was not remarkable 5 cm or more below the glottis.
3. The results mentioned above indicate that the phonic function after tracheal fenestration should be better when the tracheostoma has been made lower on the neck. Practically, fenestration should be performed 5 cm below the glottis, or at the third and fourth tracheal rings.
4. In order to obtain a phonation time more than 3 sec or a phonation time with the tracheostoma open more than 50 % of the phonation time with the fenster closed, the tracheostoma should be less than 5 mm in diameter.
5. A simpler procedure of the surgery followed by a favorable phonic function was established on the basis of the experimental results described above. It adopts a semicircular skin incision about 3 cm in diameter instead of the complicated incision in the Rockey's method.
