Difficult Mask Ventilation
Adrian A. Matioc
A 48-year-old obese woman presents for elective cholecystectomy. Her body mass index (BMI) is 45. Though she snores loudly, she has not been diagnosed with obstructive sleep apnea. She is being successfully treated for gastroesophageal reflux disease. Her airway examination appears otherwise normal. After preoxygenation for 3 minutes with a tight-fitting face mask, she is induced with propofol. Mask ventilation proves impossible.
1 What are the anesthetic and airway management considerations for this case?
The incidence of the difficult face mask ventilation (DMV) in the general population ranges between 0.05% and 15%. Langeron et al. describe five predictors for DMV—increased BMI, history of snoring/obstructive sleep apnea, lack of teeth, presence of beard, and age >55. The presence of at least two of these risk factors indicates a high likelihood of DMV. Other authors have described additional predictors: limited mandibular protrusion test, male gender, airway masses/tumors, history of radiation therapy, short thyromental distance, Mallampati score 3 to 4, and a history of failed direct laryngoscopy. The possibility of a DMV should trigger the preoperative evaluation of the triple-airway maneuver: mandibular advancement (mandibular teeth in front of the maxillary teeth), neck extension (chin up with mouth closed), and mouth opening. Other factors may affect mask ventilation in the morbidly obese patient (e.g., a restrictive pulmonary function pattern on spirometric testing, increased oxygen consumption, and reduced pulmonary compliance) (see Chapter 21).
2 How would you manage the airway in this case?
Though this case involves a patient whose difficult mask ventilation was encountered after anesthetic induction, all patients at risk should be properly readied. Thorough preoxygenation, head elevated positioning, and possibly CPAP should be employed prior to induction (see Chapter 17).
Postinduction DMV creates a critical situation that requires immediate response. The decision to proceed is dictated by the speed of desaturation and the level of experience and skill of the practitioner: