Optimal degree of mouth opening for laryngeal mask airway function during oral surgery.
OBJECTIVE
This study was performed to determine the optimal degree of mouth opening in anesthetized patients requiring laryngeal mask airway (LMA) during oral surgery.


METHODS
A single, experienced LMA user inserted the LMA in 15 patients who were scheduled for elective oral surgery. Oropharyngeal leak pressure, intracuff pressure, and fiberoptic assessment of the LMA position were sequentially documented in 5 mouth conditions-opening of 1.4 (neutral position), 2, 3, 4, and 5 cm-and any resulting ventilatory difficulties were recorded.


RESULTS
Oropharyngeal leak pressure with the mouth open 4 cm (21.8 ± 3.2 cm H(2)O, P = .025) and 5 cm (27.3 ± 7.2 cm H(2)O, P < .001) was significantly higher than in the neutral position (18.1 ± 1.5 cm H(2)O), as was intracuff pressure (neutral position, 60.0 ± 0 cm H(2)O; 4 cm, 72.6 ± 5.1 cm H(2)O [P < .001]; and 5 cm, 86.9 ± 14.4 cm H(2)O [P < .001]). LMA position, observed by fiberoptic bronchoscopy, was unchanged by mouth opening, being similar in the 5 mouth conditions (P = .999). In addition, ventilation difficulties (abnormal capnograph curves or inadequate tidal volume) occurred in 2 of 15 patients (13%) and 7 of 15 patients (53%) (P < .001) with the mouth opening of 4 and 5 cm, respectively.


CONCLUSIONS
This study showed that a mouth opening over 4 cm led to substantial increases in oropharyngeal leak pressure and intracuff pressure of the LMA, warranting caution, because gastric insufflation, sore throat, and ventilation difficulties may occur. A mouth opening of 3 cm achieves acceptable airway conditions for anesthetized patients requiring LMA.
Sanuki
Takuro
T
Department of Anesthesiology, Osaka Dental University, Chuo-ku, Osaka, Japan. odu9847@yahoo.co.jp
Sugioka
Shingo
S
Hirokane
Motoko
M
Son
Hiroki
H
Uda
Rumiko
R
Akatsuka
Masafumi
M
Kotani
Junichiro
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058109:Airway Management; D001999:Bronchoscopy; D019296:Capnography; D017558:Elective Surgical Procedures; D004825:Epiglottis / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D017214:Laryngeal Masks; D008297:Male; D008875:Middle Aged; D009055:Mouth / Q000502:physiology*; D055100:Optical Fibers; D019647:Oral Surgical Procedures; D009960:Oropharynx / Q000502:physiology; D011312:Pressure; D013990:Tidal Volume / Q000502:physiology; D014827:Vocal Cords / Q000033:anatomy & histology; D055815:Young Adult