What is the rate of tongue obstructing the airway during anesthesia?

Rate of Tongue Obstruction During Anesthesia

Upper airway obstruction due to the tongue is a significant risk during anesthesia, with studies showing an increased risk of upper airway obstruction when laryngeal mask airways are removed under deep anesthesia 1.

Mechanism of Tongue-Related Airway Obstruction

Airway obstruction during anesthesia primarily occurs due to:

• Loss of muscle tone that is normally present in the awake state 2
• Anesthetic agents inhibiting respiratory activity of upper airway muscles more than the diaphragm 3
• The velopharynx (soft palate area) being particularly narrow and predisposed to obstruction 2

Evidence on Tongue Obstruction

Research findings on tongue obstruction during anesthesia reveal:

• Contrary to traditional belief that the tongue is the primary cause of obstruction, MRI studies suggest that airway closure often occurs at the level of the soft palate 3
• The minimum anteroposterior diameter of the pharynx at the soft palate level decreases significantly during propofol anesthesia (from 6.6 mm awake to 2.7 mm anesthetized) 3
• Ultrasound assessment during induction shows that tongue movement is inconsistent in direction and relatively minimal (not more than 8 mm in anterior tongue and 6 mm in posterior tongue) 4

Risk Factors for Tongue-Related Airway Obstruction

Patients at higher risk include those with:

• History of obstructive sleep apnea or snoring 2
• Obesity 2
• Maxillary hypoplasia or mandibular retrusion 2
• Bulbar muscle weakness 2
• Specific obstructive lesions such as adenotonsillar hypertrophy 2

Management Techniques

The Difficult Airway Society guidelines recommend:

1. Preventive measures:

   • Appropriate positioning (head-up position aids airway patency, especially in obese patients) 1
   • Careful suction under direct vision with the patient deeply anesthetized 1
   • Avoiding unnecessary upper airway stimulation 1

2. If obstruction occurs:

   • Apply continuous positive airway pressure with 100% oxygen 1
   • Ensure upper airway patency using appropriate maneuvers:
     • Chin lift technique has been shown to provide the most consistently adequate airway 5
     • Jaw thrust and Larson's maneuver (pressure between the posterior border of mandible and mastoid process) 1
   • Consider nasal CPAP, which can counteract anesthesia-induced pharyngeal narrowing by functioning as a pneumatic splint 3

Monitoring and Vigilance

• Constant evaluation of airway patency, ventilation, and oxygenation is required throughout anesthesia 1
• Problems at the end of anesthesia may relate to airway obstruction, with nearly 30% of adverse events associated with anesthesia occurring at the end of anesthesia or during recovery 1

Extubation Considerations

• Planning and preparation are key issues in safe extubation 1
• In obstetric practice, tracheal extubation is usually performed when the patient is awake, responsive to commands, maintaining oxygen saturation and generating satisfactory tidal volume 1
• Head-up position during extubation is likely to aid airway patency and respiratory function 1

While specific numerical rates of tongue obstruction during anesthesia are not clearly established in the literature, the evidence indicates it is a common occurrence that requires vigilant monitoring and prompt management to prevent adverse outcomes.