The Supra Glottic Air Way Structures (Mouth, Nose & Pharynx)

The Supra Glottic Air Way Structures (Mouth, Nose & Pharynx)

Mouth

The opening of the mouth is formed by the gums and teeth inside and the lips and the cheeks outside. The mouth cavity is bounded in front by the teeth and gums, above by the hard and soft palates and below by the tongue and the mucosa between the tongue and mandible. The tongue makes up most of the floor of the mouth, which is bounded by the mandible and teeth (Figure 3.1). Non encapsulated lymphoid tissue on the posterior surface of the tongue is part of the ring of Waldeyer. This tissue is important in that hypertrophy can cause serious difficulty in airway management.

The ability to achieve good mouth opening is important for many airway procedures. The jaw-thrust maneuver, grasping the angles of the patient's lowers jaw and lift with both hands, uses the sliding component of the tempro-mandibular joint (TMJ) to move the mandible and attached structures anteriorly. Adequate mouth opening can facilitate the insertion of oropharyngeal airways, supraglottic airway devices, and laryngoscopes.

The Palate

The palate forms the roof of the mouth (Figure3.1). The mucous membrane of the hard palate is closely attached to the periosteum of the bone. The soft palate is attached to the posterior edge of the hard palate. The uvula is in the free edge of the soft palate centrally, while the lateral ends of the soft palate are continuous with the side walls of the pharynx. The front of the soft palate faces the mouth cavity. The posterior surface is part of the nasopharynx(Figure 3.2).

The Nose

The nose warms, filters, and humidifies incoming air and is the organ of smell. It consists of the external nose and the internal nasal cavity. The nasal cavities are divided by the nasal septum, which is frequently deviated with the consequence that the nasal cavities are narrowed or obstructed. The roof of the nasal cavity is the cribriform plate, a thin bone that is easily fractured, thereby resulting in communication between the nasal and intracranial cavities. Prolonged nasotracheal intubation impairs drainage through paranasal sinuses openings, causing sinusitis. The lining of the nasal cavity is very vascular, and application of nasal vasoconstrictors to shrink the mucosa and dilate the airway reduces the risk of hemorrhage during the insertion of airway devices or tracheal tubes.

An endotracheal or tracheostomy tube which bypassed the upper respiratory tract would result in cold dry gases reaching the trachea. If this continued for any length of time the cold dry gases would interfere with ciliary activity and cause tracheitis and other respiratory complication Hence patients who are intubated long term, or have a tracheostomy, must have inspired gases humidified.

The Pharynx

The adenoids are important to the anaesthetist for several reasons.

• They may swell and cause upper respiratory tract obstruction.
• Nasotracheal intubation may be difficult if adenoids are present or large.
• Infection may result in a nasopharyngeal abscess. The passage of a nasal or endotracheal tube could rupture such an abscess. This is hazardous, especially in an unconscious patient.

Pharyngeal obstruction: This is a common problem under anaesthesia and in the recovery period. The commonest cause is the tongue falling back in the unconscious patient. The following measures should be taken to overcome the problem.

• Lift the lower jaw so that the lower incisors are in front of the upper jaw.
• Hyper-extend the head.
• Insert a Guedel airway or insert a naso-pharyngeal airway.
• Place the patient in the lateral position if necessary.
• If the airway obstruction still persists intubation or insertion of a laryngeal mask (if available) may be necessary.