Preparation is mandatory for all airway manage-ment scenarios. The following equipment is rou-tinely needed in airway management situations:
· An oxygen source
· BMV capability
· Laryngoscopes (direct and video)
· Several endotracheal tubes of different sizes
· Other (not endotracheal tube) airway devices (eg, oral, nasal airways)
· Oximetry and CO2 detection
· Blood pressure and electrocardiography (ECG) monitors
· Intravenous access
Loss of upper airway muscle tone (eg, weakness of the genioglossus muscle) in anesthetized patients allows the tongue and epiglottis to fall back against the pos-terior wall of the pharynx. Repositioning the head or a jaw thrust is the preferred technique for open-ing the airway. To maintain the opening, an artificial airway can be inserted through the mouth or nose to maintain an air passage between the tongue and the posterior pharyngeal wall ( Figure 19–6). Awake or lightly anesthetized patients with intact laryngeal reflexes may cough or even develop laryngospasm during airway insertion. Placement of an oral air-way is sometimes facilitated by suppressing airway reflexes, and, in addition, sometimes by depressing the tongue with a tongue blade. Adult oral airways typically come in small (80 mm [Guedel No. 3]), medium (90 mm [Guedel No. 4]), and large (100 mm [Guedel No. 5]) sizes.
The length of a nasal airway can be estimated as the distance from the nares to the meatus of the ear and should be approximately 2–4 cm longer than oral airways. Because of the risk of epistaxis, nasal airways are less desirable in anticoagulated or thrombocytopenic patients. Also, nasal air-ways (and nasogastric tubes) should be used with caution in patients with basilar skull fractures, where there has been a case report of a nasogastric tube entering the cranial vault. All tubes inserted through the nose (eg, nasal airways, nasogastric
catheters, nasotracheal tubes) should be lubricated before being advanced along the floor of the nasal passage.
The use of a face mask can facilitate the delivery of oxygen or an anesthetic gas from a breathing sys-tem to a patient by creating an airtight seal with the patient’s face (Figure 19–7). The rim of the mask is contoured and conforms to a variety of facial features. The mask’s 22-mm orifice attaches to the breathing circuit of the anesthesia machine through a right-angle connector. Several mask designs are available. Transparent masks allow observation of exhaled humidified gas and imme-diate recognition of vomitus. Retaining hooks surrounding the orifice can be attached to a head strap so that the mask does not have to be continu-ally held in place. Some pediatric masks are spe-cially designed to minimize apparatus dead space (Figure 19–8).
Effective mask ventilation requires both a gastight mask fit and a patent airway. Improper face mask technique can result in continued deflation of the anesthesia reservoir bag when the adjustable pressure-limiting valve is closed, usually indicating a substantial leak around the mask. In contrast, the generation of high breathing circuit pressures with minimal chest movement and breath sounds implies an obstructed airway or obstructed tubing.
If the mask is held with the left hand, the right hand can be used to generate positive-pressure ven-tilation by squeezing the breathing bag. The mask is held against the face by downward pressure on the mask body exerted by the left thumb and index fin-ger (Figure 19–9). The middle and ring finger grasp the mandible to facilitate extension of the atlanto-occipital joint. This is a maneuver that is easier to teach than to describe. Finger pressure should be placed on the bony mandible and not on the soft tis-sues supporting the base of the tongue, which may obstruct the airway. The little finger is placed under the angle of the jaw and used to thrust the jaw ante-riorly, the most important maneuver to allow venti-lation to the patient.
In difficult situations, two hands may be needed to provide adequate jaw thrust and to create a mask seal. Therefore, an assistant may be needed to squeeze the bag, or the machine’s ventilator can be used. In such cases, the thumbs hold the mask down, and the fingertips or knuckles displace the jaw for-ward (Figure 19–10). Obstruction during expira-tion may be due to excessive downward pressure from the mask or from a ball-valve effect of the jaw thrust. The former can be relieved by decreasing the pressure on the mask, and the latter by releasing the jaw thrust during this phase of the respiratory cycle. It is often difficult to form an adequate mask fit with the cheeks of edentulous patients. Positive-pressure ventilation using a mask should normally be limited to 20 cm of H2O to avoid stomach inflation.
Most patients’ airways can be maintained with a face mask and an oral or nasal airway. Mask ventila-tion for long periods may result in pressure injury to branches of the trigeminal or facial nerves. Because of the absence of positive airway pressures dur-ing spontaneous ventilation, only minimal down-ward force on the face mask is required to create an adequate seal. If the face mask and mask straps are used for extended periods, the position should be regularly changed to prevent injury. Care should be used to avoid mask or finger contact with the eye, and the eyes should be taped shut to minimize the risk of corneal abrasions.
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