Proper Position for the Tip of a #4 MAC (Macintosh) Blade During Intubation
The tip of a Macintosh curved blade should be placed in the vallecula, where it depresses the hyoepiglottic ligament and indirectly lifts the epiglottis upward to expose the laryngeal inlet. 1
Mechanism of Action
The Macintosh curved blade works by:
- Inserting the blade tip into the vallecula (the space between the base of the tongue and the epiglottis) 1
- Depressing the hyoepiglottic ligament, which mechanically flips the epiglottis upward 1
- Exposing the laryngeal inlet (both epiglottis and glottis) without directly touching the epiglottis 1
The proper lifting motion is upward and toward the feet (anterocephalad direction), not a pulling back motion, to avoid using the teeth as a fulcrum 2.
Key Technical Points
For optimal results with the Macintosh blade:
- The blade tip should engage the median glossoepiglottic fold when placed in the vallecula, as this significantly improves glottic visualization (adjusted OR 3.6,95% CI 1.9-6.8) and procedural success (adjusted OR 9.9,95% CI 2.3-43.7) 3
- The lifting force should compress the root of the tongue in an anterocephalad direction in the submandibular space 2
- Avoid posterior displacement of the compressed tongue, which can worsen the view 2
Contrast with Miller (Straight) Blade Technique
The Miller straight blade uses a fundamentally different approach:
- The straight blade directly lifts the long, floppy epiglottis out of the line of sight 1
- The blade tip is placed on top of the epiglottis itself, not in the vallecula 1
- This technique requires lifting the epiglottis to visualize the glottis 1
Clinical Evidence
Recent pediatric studies comparing Miller and Macintosh blades found:
- Similar POGO scores (percentage of glottic opening) between the two blade types 1
- No difference in laryngoscopic views and intubation conditions in children under 2 years 1
- Recommendation to switch blade types if poor visualization occurs with the initial choice 1
However, when the Macintosh blade tip is placed in the vallecula, direct lifting of the epiglottis was associated with better visualization (adjusted OR 11.0 for POGO, 95% CI 5.1-23.6) compared to indirect lifting 3.
Common Pitfalls to Avoid
Do not:
- Hook or directly lift the epiglottis with a Macintosh blade—this is the Miller blade technique 1
- Pull back on the handle—this uses the teeth as a fulcrum and can cause dental trauma 2
- Place the blade "in the back of the throat and lift up"—this is too vague and doesn't describe proper vallecula placement 1
- Fail to engage the median glossoepiglottic fold when in the vallecula, as this reduces success rates 3
Answer to the Multiple Choice Question
The correct answer is: "Placed in the vallecula and pressure up and towards the feet"
This describes the proper Macintosh blade technique of vallecula placement with anterocephalad lifting force 1, 2.