Effects of head-neck extension on abnormality of laryngeal mask airway function resulting from opening the mouth.
OBJECTIVE
This study investigated the effects of head-neck extension on abnormalities of laryngeal mask airway (LMA) function resulting from opening the mouth.


METHODS
A single, experienced LMA user inserted the LMA in 15 patients scheduled for elective oral surgery. Oropharyngeal leak pressure and intracuff pressure were sequentially documented in 5 mouth conditions in order (0 minutes, mouth closed plus 0° extension; 3 minutes, mouth open plus 0° extension; 6 minutes, mouth open plus 15° extension; 9 minutes, mouth open plus 30° extension; and 12 minutes, mouth open plus 45° extension).


RESULTS
Oropharyngeal leak pressures with the mouth open plus 0° extension (30.7 ± 5.6 cm H(2)O, P < .001), mouth open plus 15° extension (29.1 ± 6.8 cm H(2)O, P < .001), and mouth open plus 30° extension (25.7 ± 6.1 cm H(2)O, P < .001) were significantly higher than with the mouth closed plus 0° extension (19.7 ± 2.8 cm H(2)O). Compared with the position with the mouth closed plus 0° extension (60.0 ± 0 cm H(2)O), intracuff pressures were also higher with the mouth open plus 0° extension (84.5 ± 14.1 cm H(2)O, P < .001), mouth open plus 15° extension (77.4 ± 11.0 cm H(2)O, P < .001), and mouth open plus 30° extension (73.6 ± 9.6 cm H(2)O, P < .001). Both measurement values returned to control levels when the position with the mouth open plus 45° extension was assumed (oropharyngeal leak pressure, 64.5 ± 6.5 cm H(2)O [P = .212]; intracuff pressure, 20.2 ± 4.9 cm H(2)O [P = .969]).


CONCLUSIONS
In procedures requiring the patient to have an open mouth under general anesthesia using LMA, 45° head-neck extension achieves acceptable airway conditions.
Department of Anesthesiology, Osaka Dental University, Chuo-ku, Osaka, Japan. odu9847@yahoo.co.jp
Takuro
T
Sanuki
Shingo
S
Sugioka
Hiroki
H
Son
Rumiko
R
Uda
Masafumi
M
Akatsuka
Junichiro
J
Kotani
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058109:Airway Management; D019296:Capnography; D017558:Elective Surgical Procedures; D005260:Female; D006257:Head / Q000033:anatomy & histology*; D006801:Humans; D017214:Laryngeal Masks; D008297:Male; D008875:Middle Aged; D009055:Mouth / Q000502:physiology*; D009333:Neck / Q000033:anatomy & histology*; D019647:Oral Surgical Procedures; D009960:Oropharynx / Q000502:physiology; D056888:Patient Positioning; D011187:Posture / Q000502:physiology; D011312:Pressure; D012119:Respiration; D013990:Tidal Volume / Q000502:physiology; D013997:Time Factors; D055815:Young Adult