What are the risks of placing a McIntosh (laryngoscope) too deep during tracheal intubation?

Risks of Placing a Macintosh Laryngoscope Too Deep During Tracheal Intubation

Placing a Macintosh laryngoscope too deep during tracheal intubation can cause significant airway trauma, worsen laryngeal view, and increase the risk of failed intubation, potentially leading to serious morbidity and mortality.

Anatomical Consequences of Deep Insertion

When a Macintosh laryngoscope is inserted too deeply, several immediate problems occur:

1. Worsened laryngeal view:

   • The blade tip can advance beyond the vallecula into the esophagus
   • This pushes the epiglottis downward rather than lifting it, obscuring the glottic view
   • Results in a poorer Cormack-Lehane grade (grade 3 or 4 view) 1

2. Airway trauma risks:

   • Damage to soft tissues of the oropharynx and larynx
   • Dental trauma from excessive force when attempting to improve the view
   • Increased risk of bleeding, which can further compromise the airway 1

Clinical Impact on Intubation Success

Deep insertion of the Macintosh blade significantly impacts intubation success:

• Increased failure rate: Guidelines indicate that failed first attempts often result from improper laryngoscope positioning 1
• Multiple attempts required: Necessitating repeated laryngoscopy, which increases trauma risk 1
• Prolonged intubation time: Leading to potential hypoxemia, especially in high-risk patients 1

Specific High-Risk Complications

1. Airway trauma:

   • Soft tissue damage to the posterior pharyngeal wall
   • Laceration of the vallecula or piriform fossae
   • Damage to the arytenoid cartilages 1

2. Hypoxemia risk:

   • Failed or prolonged intubation attempts increase desaturation risk
   • Guidelines emphasize that desaturation <95% requires cessation of intubation attempts in favor of oxygenation 1

3. Cervical spine movement:

   • Excessive force with deep insertion may cause greater cervical spine movement
   • Particularly dangerous in patients with suspected cervical spine injuries 1

Corrective Measures

If a poor view is obtained due to deep insertion:

1. Withdraw the blade tip to the correct position in the vallecula (between the base of the tongue and epiglottis)

2. Apply optimal external laryngeal manipulation (OELM) or BURP (backward, upward, rightward pressure) to improve the view 1

3. Consider alternative approaches:

   • Use of a bougie or stylet if partial view is obtained
   • Switch to videolaryngoscopy which has been shown to improve glottic view and increase first-pass success 2
   • Consider using a different blade design if appropriate 1

Prevention Strategies

To avoid deep insertion complications:

• Proper technique: Insert the Macintosh blade following the natural contour of the tongue until the epiglottis comes into view
• Correct positioning: Place the tip of the blade in the vallecula, not beyond it
• Appropriate blade size: Select the correct blade size for the patient
• Consider videolaryngoscopy: Modern guidelines recommend having videolaryngoscopy immediately available, as it provides better glottic views than direct laryngoscopy 1, 2

Special Considerations

• Difficult airways: In patients with predicted difficult airways, deep insertion of a Macintosh blade carries even higher risks of failed intubation 1
• Cervical spine concerns: Deep insertion with excessive force may cause greater cervical spine movement, potentially dangerous in trauma patients 1

Remember that proper positioning of the Macintosh blade in the vallecula is crucial for successful laryngoscopy. If difficulty is encountered, early transition to alternative techniques rather than forceful deeper insertion is recommended to reduce morbidity and mortality risks.