Airway obstruction
An obstructed airway can be caused by tumours, infection, and trauma anywhere in the airway, from the nasopharynx, pharynx, and larynx through to the lower trachea and lower airways. Management strategies remain controversial, and experts frequently disagree on the best strategy. For adults, there are advocates of inducing general anaesthesia by an inhalational route and avoiding muscle relaxants, inducing general anaesthesia by the IV route and using muscle relaxants, avoiding general anaesthesia altogether and securing an airway by an awake fibreoptic intubation (AFOI) technique, tracheostomy under local anaesthesia, or insertion of a transtracheal catheter under local anaesthesia.
The recognition of a compromised or an anatomically distorted upper airway is vital in the preoperative assessment of head and neck patients. For elective patients, detailed investigations can be undertaken, but, in urgent cases, this may not be possible.
The exact technique chosen will be influenced by the urgency of the intervention required, the experience of the anaesthetist, the team around them, the location, surgical experience, and the site and extent of the airway obstruction. All plans can fail, and backup plans should have been discussed amongst the team, with the relevant equipment being available.
There are three questions that determine the management of the obstructed adult airway. First, what and where is the lesion? Second, how urgent is the intervention? Third, is the obstruction so significant that we should abandon attempts for general anaesthesia and use an awake technique?
1 Recognize the pathological causes of an airway obstruction
2 Define the level and severity of the obstruction
3 Describe the safe conduct of fibreoptic-guided airway management.
2A01; 2A03
A 54-year-old woman presented with a large neck mass and a vocal cord palsy on the left side. She was unable to lie flat for prolonged periods, because of the difficulty in breathing, and preferred to sleep semi-upright on her left side. She had been unable to walk >20 yards without stopping and was now unable to climb her stairs at home. She had an RR of 16 breaths/min at rest and oxygen saturation readings of 95% on air. An urgent CT scan showed a large thyroid mass which was flattening the trachea to a minimal diameter of 8 mm, but no obvious local invasion into the trachea.
A 68-year-old man presented to the ED with increasing difficulty in breathing over the last week and was now unable to speak in full sentences. Past medical history included a hypopharyngeal carcinoma treated with surgical resection and radiotherapy 3 years previously. Over the last 24 hours, the breathing had become particularly difficult, and he was now unable to walk up his stairs at home. On examination, he had inspiratory stridor, tracheal tug, an RR of 26 breaths/min, and oxygen saturation readings of 86% on air. Careful experienced flexible nasendoscopy revealed an ulcerated mass on the left vocal cord which was obstructing approximately 70% of the laryngeal inlet.
Case 1: a large neck mass suggests thyroid involvement which can extend into the mediastinum. If there is mediastinal involvement, there may be associated large vessel obstruction, and surgery may involve resection of the manubrium for access. Recurrent laryngeal nerve function may be compromised with expanding neck and thyroid masses
Case 2: this is likely to be a recurrence of the hypopharyngeal tumour or an infective process involving the area of previous surgical resection and radiotherapy.
The differential diagnosis of any upper airway obstruction varies according to age and the history of presentation. Benign or malignant tumours in any anatomical part of the upper airway or extrinsic compression from mediastinal masses can cause compression, luminal obliteration, or vocal cord palsy. Infection can be due to a retropharyngeal abscess, acute tonsillitis, Ludwig’s angina, epiglottitis, laryngotracheobronchitis (croup), and diphtheria. Trauma, foreign bodies, haemorrhage, facial trauma, laryngeal stenosis, burns, laryngotracheal stenosis, angio-oedema, anaphylaxis, and vocal cord paralysis can all cause airway obstruction.
Case 1: the woman has a large thyroid mass that is causing compressive symptoms on the trachea which is resulting in difficulty of breathing. She does not need immediate intervention, and further investigations can be carried out. She will need a resection of the thyroid mass under general anaesthesia. There is compression of the trachea, and this may be worse following induction of anaesthesia. If laryngoscopy and tracheal intubation proves to be difficult or impossible, the option of an urgent surgical airway (plan B) would not be possible with a large mass overlying the neck. Under these circumstances and without the option of a surgical plan B, this patient should have an AFOI
Case 2: a recurrence of the carcinoma with extensive laryngeal obstruction is present. Urgent stabilization and intervention are required. Initial medical management with careful observation includes humidified oxygen, nebulized adrenaline, IV corticosteroids, and helium/oxygen mixtures if further deterioration in breathing occurs. Helium/oxygen is used as a temporary ‘holding’ measure whilst preparations are made for a definitive surgical intervention.
The level at which obstruction exists makes a significant difference as to the suitability of different techniques. For obstructing oral cavity lesions, the problems are first the ability to face mask-ventilate following induction of anaesthesia and, second, the difficult or impossible direct laryngoscopy around obstructing masses. At the glottis, the most common cause of obstructing lesions are tumours, and, as they enlarge, patients compensate until either an acute deterioration or a critical narrowing is reached. The key decision is to identify if it will be possible to pass a tracheal tube through the narrowing, and, if this is felt to be unlikely, an awake transtracheal catheter or awake local anaesthetic tracheostomy should be considered. Tracheal compression can occur as a result of lesions within the trachea or compression from thyroid and mediastinal masses. The upper airway may be normal at laryngoscopy, but it may not be possible to pass a tube beyond the obstruction or place a surgical airway beyond the obstruction.
The differences between airway noises can help establish the level of obstruction, but, in severe obstruction, as the airflow becomes more restricted, the noise of breathing may disappear. An obstruction at a nasopharyngeal level typically produces a stertorous sound and at an oropharyngeal level a gurgling sound. Stridor is a high-pitched sound, and inspiratory and expiratory stridors represent extrathoracic and intrathoracic obstructions. In severe obstruction and with exhaustion, the noise will diminish.
A full history and investigations to determine the site and extent of the obstruction and determine all the other factors associated with difficult airway management should be sought. Old anaesthetic records, imaging, and careful flexible nasendoscopy will provide useful information. The aim is to balance the urgency of the clinical situation but to provide anaesthesia in a planned manner. In an emergency, it may be necessary to proceed without the full clinical picture.
Case 1: an AFOI is performed, with the patient sitting up. This should be performed by an experienced endoscopist, with optimal topical local anaesthetic. A ‘spray as you go’ technique will be required to topicalize the trachea, because intratracheal injections will not be possible in a patient with a large neck mass overlying the trachea
Case 2: surgical intervention to debulk the tumour under general anaesthesia with a microlaryngoscopy tube was planned urgently. Experienced surgical and anaesthetic staff were involved, and all equipment was checked and plans made for emergency surgical tracheal access. The anaesthetic plan involved the introduction of an awake transtracheal catheter under local anaesthetic. After the introduction and confirmation of correct placement of the transtracheal catheter, IV induction of anaesthesia with propofol, fentanyl, and rocuronium was undertaken. Face mask ventilation using oxygen FiO2 1.0 was possible, and anaesthesia was maintained using sevoflurane 2–4% in oxygen. Direct laryngoscopy allowed the introduction of a size 4 laser-resistant tube. Surgery involved laser debulking of the mass, and, at the end of the case, he was extubated in a head-up position, fully awake.
Fibreoptic intubation is a complex highly skilled technique and should only be used in a critical airway by those familiar with it, as the risks of total airway obstruction and trauma are higher in inexperienced hands. In patients with severe glottic or subglottic narrowing, there is a significant risk of total airway blockage as the fibrescope is passed, and it may not be possible to railroad a tube past the obstruction. The recent National Audit Project 4 identified 14 failed intubations in 23 fibreoptic intubation attempts in patients with head and neck pathology, of which almost all required a surgical airway. AFOI is particularly useful when there may be difficulty with face mask ventilation or with direct laryngoscopy.
Anterior neck access by a transtracheal cannula, designed for tracheal access, can be inserted in elective, as well as more urgent, cases typically into the upper trachea between the tracheal rings, avoiding the cricothyroid area where there may be tumour extension. It is then possible to insufflate oxygen or use jet ventilation techniques via the cannula. The ability to oxygenate prior to the induction of general anaesthesia allows time for airway manipulations, so that difficult laryngoscopy is not rushed and is optimal with the highest success rates.
With severe airway compromise, sedation or general anaesthesia may, in some patients, cause total airway obstruction. This may not be relieved with airway manoeuvres, and direct laryngoscopy or flexible fibreoptic attempts at intubation may not be possible. Under these circumstances, any sedation, general anaesthesia, or attempts at airway intervention result in a patient in which we cannot ventilate or intubate. Under these circumstances, an awake tracheostomy performed by an experienced surgeon is the safest method of airway management. The ideal position for a surgical tracheostomy is supine with the neck extended, but, in severe airway compromise, this is not possible. Typically, a patient for an awake tracheostomy cannot lie flat or extend the neck, and so the procedure is undertaken in a semi-recumbent or an upright position. Oxygen should be administered throughout, and there must be no sedation or anaesthesia during the awake tracheostomy. The implicit safety of an awake tracheostomy is that the patient is awake. Any sedation or anaesthesia risks total airway obstruction and conversion of a difficult, but controlled, awake surgical tracheostomy into an immediate uncontrolled surgical tracheostomy.
Summary
Management strategies for airway obstruction remain controversial, and experts frequently disagree on the best strategy. Generally, three questions determine the management of the obstructed adult airway. First, what and where is the lesion? Second, how urgent is the intervention? Third, is the obstruction so significant that we should abandon attempts for general anaesthesia and use an awake technique? Fibreoptic intubation is a complex, highly skilled technique and should only be used in a critical airway by those familiar with it, as the risks of total airway obstruction and trauma are higher in inexperienced hands. With severe airway compromise, sedation or general anaesthesia may, in some patients, cause total airway obstruction. Under these circumstances, an awake tracheostomy performed by an experienced surgeon is the safest method of airway management.
Patel A and Pearce A (2011). Progress in management of the obstructed airway. Anaesthesia, 66, 93–100.
Patel A, Pearce A, and Pracy P (2011). Head and neck pathology. In: Cook T, Woodall N, and Frerk C, eds. 4th national audit project of the Royal College of Anaesthetists and the Difficult Airway Society: major complications of airway management in the United Kingdom, pp. 143–54. Royal College of Anaesthetists, London.