Chapter 16: Perioperative care
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Airway management
Definition
Airway management is the planning and performance of manoeuvres and procedures that anticipate, prevent and relieve airway obstruction. It is one of the cornerstones of safe anaesthetic practice.
Related theory
When a supine patient is rendered unconscious with anaesthesia, the soft tissues of the tongue and neck relax, and occlude the laryngeal inlet. This can cause an obstruction of the airway.
The purpose of airway management during anaesthesia and surgery is to maintain patency of the airway, thereby facilitating effective ventilation of the patient's lungs. Assessment of the patient's airway prior to anaesthesia is vital in order for the anaesthetist to plan and prepare the most appropriate airway management strategy (Bradley et al. [36]). A complete airway assessment includes the patient's history (e.g. history of previous airway difficulties during anaesthesia or history of obstructive sleep apnoea) and a bedside examination (looking for congenital or acquired features that may make face‐mask ventilation, airway adjunct placement or tracheal intubation difficult). The Mallampati test is a subjective evaluation of the ratio of oral cavity volume to tongue volume (Mahmoodpoor et al. [114]). The test is performed on a sitting patient with the head in a neutral position, mouth fully opened and tongue extended. It involves evaluating the visibility of the uvula, as shown in Figure 16.16. Any potential difficulties of laryngoscopy and tracheal intubation can then be assessed, with a class 1 airway being the easiest to manage and control by intubation, and a class 4 airway being potentially the most difficult.
Figure 16.16 Mallampati classification of the airway.
There are several techniques for planning for airway management during the induction period. A combination of these techniques can be used if one is inadequate during a difficult intubation:
- face‐mask ventilation
- supraglottic airway ventilation
- endotracheal intubation
- fibreoptic intubation.
Face‐mask ventilation
This is a fundamental technique for safe anaesthesia and requires the practitioner to use simple airway manoeuvres (such as jaw thrust, chin lift) to open the airway. Simple adjuncts such as a Guedel airway may be useful at this stage. If the patient is apnoeic, the practitioner can deliver ventilation via an appropriate breathing circuit and a face‐mask that is held to create a tight seal with the patient's face. Difficulties with face‐mask ventilation may be encountered in a number of scenarios: inexperienced practitioner, high body mass index, the presence of a beard, facial deformities or an edentulous patient.
Supraglottic airways
The laryngeal mask airway (LMA) was developed in 1988 by Dr Archie Brain and provides an effective alternative to face‐mask ventilation in a starved patient. It is a type of supraglottic airway, which means that nothing passes through the vocal cords. Second‐ and third‐generation LMAs have since been developed, offering improved seals around the laryngeal inlet and increased flexibility in their applications. Different sizes are available depending on the patient's weight.
Endotracheal intubation
Endotracheal tubes have become fundamental to the practice of anaesthesia with the advent of neuromuscular blockade. Tubes are available in a number of sizes and styles depending on the weight of the patient and also features of the airway and surgical requirements. The trachea can be intubated with an endotracheal tube in a number of different ways: conventional direct laryngoscopy, video laryngoscopy, fibreoptic laryngoscopy or through a supraglottic airway, to name just a few.
Endotracheal intubation is a skill that requires specialist training. Techniques and devices to facilitate successful intubation of the trachea include optimal patient positioning, external laryngeal manipulation, stylets or bougies, and use of advanced airway equipment.
