Mask ventilation is an effective, noninvasive means of providing ventilation and oxygenation in the decompensated or unconscious patient. Maintenance of a patent airway with mask ventilation is an important skill that requires understanding and experience to perform well. Furthermore, the ability to ventilate by mask is life-supporting or even life-saving when direct laryngoscopy proves difficult. In some scenarios, ventilation by mask may be all the airway management necessary to ensure temporary oxygenation and ventilation, while a reversible condition is addressed, and the patient is expected to then resume spontaneous ventilation. When endotracheal intubation is necessary in the elective, fasted setting, as in the operating room, initial ventilation with the face mask should precede attempts at intubation in the apneic patient.

In emergent airway management scenarios, face mask ventilation is often withheld after unconsciousness is induced, in order to avert gastric insufflation and the potential for regurgitation (“rapid sequence induction” or “rapid sequence intubation”). However, the decision to withhold mask ventilation after the delivery of drugs for an emergent intubation is somewhat controversial.¹ In a conscious patient who is dyspneic and hypoxemic, assistance of ventilation with positive pressure or simply high-flow oxygen is appropriate to obtain adequate preoxygenation in preparation for intubation. In an unconscious patient with a reduced oxygen saturation, a period of low-pressure mask ventilation is necessary to avert severe hypoxemia during attempted laryngoscopy, and it should continue after the delivery of the hypnotic and relaxant if high oxygen saturations cannot be restored. Such attempts should be conducted in association with cricoid pressure to reduce gastric insufflation.² An assortment of face masks for ventilation is shown in Fig. 2-1. Clear masks are preferred to other types, so that regurgitation or vomitus is immediately apparent.

Effective mask ventilation requires an open airway and a tight seal between the mask and the face. Patency of the airway can be optimized with a “triple airway maneuver” in which chin lift, head extension, and mouth opening are provided. Placement of the patient in “sniffing position,” with the cervical spine flexed and the head extended, also contributes to this. Mask fit can be optimized with the choice of mask shape and with appropriate inflation of the air-filled bladder, or cushion, which surrounds most modern ventilation masks. As the mask is placed over the mouth and nose, it is imperative that pressure is applied from above as the jaw is lifted into the mask. This is most effectively performed by using the thumb and forefinger of the left hand to apply the mask, while the remaining fingers pull the boney mandible upward. This chin lift-jaw thrust maneuver prevents the soft tissue obstruction of the airway that will occur if the mandible is displaced in a posterior direction with mask pressure in the unconscious patient, or if the fingers apply pressure to the floor of the mouth, obstructing the oral cavity.³ It is particularly useful to “hook” the fifth finger behind the angle of the mandible to aid in lifting it upward. When attempting to open the airway for bag-mask ventilation, it is important to avoid firm occlusion of the teeth by cephalad pressure with the fingers on the body of the mandible, because it will be impossible to thrust the jaw forward. When making a seal proves difficult, a two-hand technique is preferred. This may utilize the thumb-forefinger technique on the mask, as described above, or the thenar eminences and thumbs may be used for downward pressure, while the other eight fingers are placed on the jaw and behind the angle of the mandible to provide jaw thrust and chin lift.

Mask ventilation also necessitates a source of pressure to move gas into the airway. Depending upon the setting, the oxygen source in bag-mask ventilation may be a hospital wall source, oxygen tank with regulator, or an anesthesia machine and circuit. Effective ventilation is confirmed by visible chest rise and audible breath sounds, as well as the presence of exhaled CO₂, if monitored (as is typical in the operating room). In addition, the “feel” of the ventilation bag may provide clues to a patent airway—when little or no resistance is met to attempts at ventilation, a leak is likely. When compliance is very poor and high pressures (more than 25 to 30 cm H₂O) are required, there is likely to be an upper airway obstruction. Additional causes of high ventilation pressures that should be considered are gastric insufflation, pneumothorax, “stacking” of breaths due to insufficient time for exhalation, and poor lung or
chest wall compliance. High inflation pressures may contribute to gastric insufflation and regurgitation and should be avoided if possible.

Airway obstruction in the unconscious individual is usually attributed to relaxation of the tongue, with posterior displacement of its muscular mass, occluding the airway at oropharyngeal levels. Studies with magnetic resonance imaging in sedated adults suggest that the soft palate plays a very important, and perhaps predominant, role in this phenomenon.⁴ Doubtless, both mechanisms may contribute, and overcoming this obstruction is paramount in ensuring oxygenation and ventilation. Either oropharyngeal or nasopharyngeal airways should be used to complement mask ventilation when obstruction occurs, and if ineffective, both may be used together (Figs. 2-2, 2-3, 2-4, 2-5, 2-6 and 2-7). Both of these aids must be sized appropriately, or else they may become ineffective or even make obstruction worse.

Various definitions of difficult mask ventilation (DMV) have arisen in the literature, but most include the need to resort to two provider assisted mask ventilation along with the clinical signs of oxygen desaturation and inadequate CO2 exchange, in the setting of poor chest excursion. At times, mask ventilation may remain difficult or impossible despite optimal technique (Figs. 2-8 and 2-9

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