What Is a Critical Mouth Opening for Macintosh Videolaryngoscopy? Results From a Prospective Observational Study
Authors' conclusion
Our findings suggest that among individuals with expected difficult airway management, interincisor distances below 21 to 23 mm indicate increased risk of Macintosh videolaryngoscopy failure and may warrant alternative or awake techniques.
Study context
- Population
- Adults at increased risk for difficult Macintosh videolaryngoscopy undergoing head and neck surgery, managed with Macintosh videolaryngoscopy (C-MAC) as first-choice technique
- Participants
- 192 adults
- Outcome
- Critical lower limits of interincisor distance optimally predicting difficult Macintosh videolaryngoscopy or risk of Macintosh videolaryngoscopy failure (Youden index, mean deviation from maximum Youden index across indicators)
Main finding
As reported in the abstract
Incidence of difficult videolaryngoscopic intubation
56.8%
109/192
Optimal discrimination easy vs difficult Macintosh videolaryngoscopy (best mean Jd-max): interincisor distances
23 and 35 mm
Incidence of failed Macintosh videolaryngoscopy (clear inverse correlation with interincisor distance)
26.0%
50/192
Optimal discrimination low vs high risk of Macintosh videolaryngoscopy failure (best mean Jd-max): interincisor distances
21 and 23 mm
Observational data: associations, not effects.
Further findings
| Outcome | OR (CI) | P value | |
|---|---|---|---|
| Risk of reduction in mouth opening after induction, by diagnosis (vs reference category)Degenerative cervical joint diseases vs reference category · highest risk | 6.43 (1.27–32.5) | P = 0.02 | |
| Risk of reduction in mouth opening after induction, by diagnosis (vs reference category)Facial fractures vs reference category · lowest risk | 0.27 (0.08–0.92) | P = 0.04 | |
| 0.050.21520Odds ratio (log scale) |
Change in interincisor distance after anaesthesia induction · after anesthesia induction
- Increased
- 31.8% (61/192)
- Unchanged
- 17.2% (33/192)
- Decreased
- 51.0% (98/192)
Original publication
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