Postoperative management of the difficult airway

Transcription

1 BJA Education, 17 (7): (2017) doi: /bjaed/mkw077 Advance Access Publication Date: 15 February 2017 Matrix reference 1C01, 2A01, 3A01 Postoperative management of the difficult airway B Batuwitage MBBCh MRCS FRCA 1, * and P Charters MD MRCP FRCA 2 1 Consultant Anaesthetist, Portsmouth Hospitals NHS Trust, Southwick Hill Road, Cosham, Portsmouth PO6 3LY, UK and 2 Consultant Anaesthetist, Aintree University Hospital Foundation Trust, Longmoor Lane, Liverpool L9 7AL, UK *To whom correspondence should be addressed. bisanth.batuwitage@porthosp.nhs.uk Key points Airway obstruction in the postoperative period is associated with a high incidence of morbidity. A strategy on how to manage the difficult airway after surgery should be agreed by the multidisciplinary team. The Difficult Airway Society guidelines should be followed for at risk patients, with the consideration of advanced techniques. Patients at risk of deterioration should be observed and monitored closely after surgery for signs and symptoms of airway compromize and the need for re-intubation. If there is significant concern about the patency of the airway then the patient should either remain intubated or have a tracheostomy. In recent years, there have been major advances in airway management, including the development of intubation guidelines and recognition of the importance of human factors and nontechnical skills. 1,2 It is important to appreciate that airway management continues into the postoperative period and that the incidence of airway problems during emergence and accounts for significant morbidity. The fourth National Audit Project of major airway complications identified a number of reported events at the end of surgery. 3 A similar finding was found in an analysis of the ASA closed claims database. 4 It is therefore essential that a clear plan is formulated for management of the difficult airway after surgery. The Difficult Airway Society (DAS) guidelines 5 identifies at risk patients and provides a useful framework for managing difficult airways. These patients will often be managed on the intensive care unit (ICU), and good communication between anaesthetists, surgeons, and intensivists is essential to decision making. Predicting postoperative difficulty General If there has been difficulty with the initial intubation then may also prove to be difficult. It is important to consider the airway at the end of surgery because trauma and resultant oedema may cause life-threatening airway obstruction. Obese patients are at increased risk of postoperative airway complications. If there is a history of obstructive sleep apnoea (OSA) then return of airway tone may be delayed, and consideration to postoperative airway support such as non-invasive ventilation and the use of a nasopharyngeal airway should be considered. OSA patients may already have a continuous positive airway pressure (CPAP) machine at home and should be asked to bring this equipment to hospital so it can be used during the perioperative period. Those patients who are at risk of aspiration (e.g. emergency patients, gastro-oesophageal reflux disease) may benefit from decompression of the stomach with a nasogastric tube before. The accessibility of the trachea is important, and this may preclude if there is a concern about the ability to reintubate the patient. The diagnosis of unrelieved trismus (e.g. because of fibrosis) may also raise the possibility of difficulty. A laryngeal mask airway or oral tube may be totally occluded by the patient biting on it during emergence from anaesthesia; the use of a oropharyngeal airway or bite block (e.g. rolled gauze) can mitigate this risk. Editorial decision: November 26, 2016; Accepted: December 5, 2016 VC The Author Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please journals.permissions@oup.com 235

2 At induction Difficult mask ventilation at induction may predict problems during emergence. This may be because of facial asymmetry, airway pathology (e.g. tumour masses), sleep apnoea, increased BMI, bull neck, Mallampati grade 3/4, male gender, age >55 yr, beards, or limited jaw protrusion. It has been argued that avoiding muscle relaxants before establishing ease of bag-and-mask ventilation initially gives useful information as to how the emergent airway will behave. If difficult bagand-mask ventilation is found then the option of waking the patient or using a short-acting neuromuscular blocking drug can be used. This, however, remains controversial as there is a growing body of evidence that neuromuscular block makes facemask ventilation more effective and therefore should be given early. 6 Surgical factors Table 2 lists surgical procedures that may cause problems after surgery. This is more common in head and neck surgery where the airway has been changed from the preoperative state but it may also be seen where patient positioning has resulted in oedema (e.g. prone positioning, steep Trendelenburg). Similarly, Vasalva manoeuvres (coughing and straining) and change from sitting upright to supine posture may make the at risk airway suddenly obstruct because of increased oedema. If it is clear that the airway may be compromised and that oxygenation may be difficult or if re-intubation may also be hazardous then the patient should remain intubated or have a tracheostomy. This will depend on the availability of local resources. Anaesthetic factors There are a number of requirements that are necessary before safe of the difficult airway and these should be met (Table 3). Incomplete reversal of neuromuscular blocking agents and excessive opioid use may result in airway obstruction and resultant hypoxia. The different muscle recovery rates after neuromuscular block (e.g. diaphragm then upper airway muscles) makes monitoring for residual effects in difficult airway patients essential; therefore, quantitative neuromuscular monitoring has recently been recommended. 7 The postoperative obstructed airway may also lead to postoperative negative pressure pulmonary oedema, which can be life threatening if not managed expeditiously. Postoperative airway management should be an informed decision that incorporates preoperative information and pre assessment in conjunction with knowledge gained from techniques that were successful and those that were Table 1 Causes of postoperative airway obstruction Laryngospasm Laryngeal oedema (e.g. prolonged Trendelenburg position) Vocal cord paralysis Reduced venous drainage Bleeding into the airway (including clots blocking the inlet) Local infection Neck haematoma Foreign body (e.g. retained throat pack) Obesity/obstructive sleep apnoea Inadequate reversal of neuromuscular blocking drug unsuccessful during the initial management of the patient s airway. Factors affecting airway management strategy History A clear history of the patient s symptoms may help in deciding how to manage the airway after surgery. If there are symptoms of airway obstruction such as stridor, hoarseness of voice, or difficulty managing secretions (drooling) then this would usually preclude. Preoperative nasendoscopy is useful as it provides important information of the starting airway. In patients where the postoperative strategy is less obvious, an airway assessment is essential before deciding on how to proceed. The simplest way of doing this is by starting at the mouth and working down. Examination It is important to ensure that general factors are assessed such as haemodynamic status, respiratory function, metabolic factors, and level of consciousness. Table 2 Surgical operations associated with postoperative airway compromise Neck pathology (bleeding after neck dissection/ thyroidectomy; postoperative carotid blow out) Tongue biopsy Tonsillectomy Pan-endoscopy (reactive cord oedema) Radical neck dissection (tied Internal Jugular vein (IJV), likelihood of vocal cord oedema attributable to venous congestion) Operations on the cervical vertebrae (multi-factorial) Infections (dental abscess, Ludwig s angina, incomplete drainage, or disease progression) Abnormal airway morphology tumour still present (biopsy/examination under anaesthesia only for diagnosis) De-bulking tumour issues continued oozing/ redundant tissue obstructing narrow glottis Oedema following surgery bi-maxillary osteotomy, any major airway surgery Surgical packing of nose (less common) Table 3 Suggested technique for awake of the difficult airway Position patient appropriately/ sit up Skilled assistance Direct suctioning of the airway Airway adjunct/bite block (e.g. rolled gauze) 100% Oxygen Ensure cardiovascular stability Ensure adequate gas exchange/regular breathing Reversal of neuromuscular blocking agents Adequate analgesia (avoiding excessive or insufficient) Patient awake and eye opening/obeying commands Apply positive pressure, deflate cuff and remove tube Ensure airway patency Continue with oxygen delivery Safe transfer/high flow oxygen/close observation and monitoring 236 BJA Education Volume 17, Number 7, 2017

3 Face/oropharynx If there is obvious swelling to the face (e.g. from steep head down positioning) or tongue (e.g. from a mouth gag) then this may precipitate postoperative airway obstruction. Supraglottic/larynx This should be examined at the end of surgery by direct or indirect laryngoscopy. This will allow any intra-operative changes to be identified such as airway oedema, bleeding, or surgical distortion. Particular consideration of clots in the postnasal space is important because they may dislodge after and obstruct the laryngeal inlet. It is important to realize the tracheal tube will distort the assessment of the postoperative airway. It is likely that oedema will re-distribute and inflammation will worsen if already established. Subglottis The subglottic region can be assessed by a cuff leak test. This involves deflating the tracheal tube cuff in order to assess the leak of air around the tube. This will give an assessment of upper airway patency and is more commonly used on critical care where the cuff leak volume (defined as the difference between the inspiratory tidal volume and the averaged expiratory tidal volume while the cuff around the tracheal tube is deflated) can be recorded. A cuff leak volume less than 110 ml has been shown to be predictive of post stridor. 8 The presence of a leak is suggestive of space around the tracheal tube; however, the redistribution of oedema may mean that this test is no guarantee of airway patency. A meta-analysis concluded that the absence of a leak should alert the clinician to a higher risk of upper airway obstruction; however, the presence of a leak has a low predictive value and does not rule out the occurrence of upper airway obstruction. 9 There have been several studies examining the use of ultrasound to assess airway patency. The air column width (ACW) is defined as the width of the acoustic shadow measured at the level of the vocal cords. The ACW is measured before and after cuff deflation allowing the air column width difference (ACWD) to be calculated. A higher ACWD has been associated with fewer airway complications. The current evidence for the use of ultrasound suggests that it is unreliable, with a low positive predictive value, sensitivity and specificity, is limited to smallscale studies and therefore results should be interpreted with caution. 10 Lower airway The simplest method of assessing the lower airways is clinical examination with auscultation of the chest and radiographs taken if there is clinical suspicion. Endobronchial intubation may cause lobar collapse. If the patient has an episode of postoperative pulmonary oedema or aspiration this may show as bilateral pulmonary infiltration. The importance of gastric aspiration was highlighted in the NAP 4 report. 3 Trauma to the airway may result in surgical emphysema or a pneumothorax. The presence of gastric distension is common when bag-andmask ventilation has been difficult and this may splint the diaphragm. This is more commonly seen in paediatrics where it may impede spontaneous breathing. The stomach can be decompressed with a nasogastric tube before if this is considered likely. Front of neck access The presence of surgical frames (e.g. halo frame), swelling, or infection may mean that emergency front of neck access in the event of failed is impossible. If there is any uncertainty of the ability of the patients to maintain oxygenation and to re-intubate then it may be safer to keep these patients asleep, transfer them to the intensive care unit, and extubate when the clinical picture has improved. Investigations/magnetic resonance imaging The use of magnetic resonance imaging (MRI) of the airway before may provide useful information on potential difficulties including oedema and inflammation. In patients with Ludwig s angina and deep infection of tissue planes MRI imaging will clarify whether the infection is still spreading and whether there is any evidence of mediastinitis. Airway management strategy Extubation The decision whether to extubate will depend on the pathology and the risk of airway obstruction. If an airway adjunct is considered necessary then it is better to wake the patient up with one in place. The patient should be extubated ideally where they were intubated (i.e. on the operating table) with the equipment used immediately available. The use of humidified oxygen and nebulized epinephrine may help in patients who have some degree of laryngeal oedema after. The optimal dosage is unclear, although 1 mg of epinephrine in 5 ml of normal saline has been suggested. 11 The use of high flow humidified oxygen treatment such as Trans-nasal High flow Rapid Inspiratory Ventilatory Exchange (THRIVE) may have a role. 12 This treatment is ineffective in total airway obstruction and any deterioration requires a clearly communicated strategy for reintubation. These patients should be monitored closely, ideally in recovery or in a critical care area with early intervention if the airway deteriorates. The evidence suggests that in intensive care patients there is little to choose between to non-invasive ventilation vs high flow nasal oxygen. 13 The DAS guidelines suggest three advanced techniques when extubating the at risk airway (Fig. 1). Laryngeal mask airway In this technique, the tracheal tube is replaced with a laryngeal mask airway (LMA), which allows patency of the upper airway to be maintained. It is a useful technique as it allows a smoother emergence from anaesthesia, potentially reducing coughing and associated increased venous pressure, which may disrupt the surgical repair. The LMA may also protect the airway from blood and secretions in the mouth. It is not a recommended technique in patients who may be difficult to reintubate or those with a risk of aspiration as the LMA may not perform effectively (inadequate seal or unable to apply positive pressure ventilation). Ideally, the correct seating of the LMA at the laryngeal inlet should be checked with a fibrescope before starting reversal of anaesthesia. This will facilitate reintubation with an Aintree exchange catheter, should this be considered necessary. Remifentanil The ultra-short-acting opioid remifentanil can be used at the end of surgery to obtund coughing and facilitate awake. The infusion can be started at the end of the surgery, while the maintenance agent (e.g. propofol or volatile) is stopped and the patient allowed to wake up and breathe spontaneously. BJA Education Volume 17, Number 7,

4 DAS Extubation Guidelines: At risk algortithm Step 1 Plan Plan Assess airway and general risk factors At risk Ability to oxygenate uncertain Reintubation potentially difficult and/or general risk factors present Step 2 Prepare for Prepare Optimize patient and other factors Key question: is it safe to remove the tube? Optimize patient factors Cardiovascular Respiratory Metabolic / temperature Neuromuscular Optimize other factors Location Skilled help / assistance Monitoring Equipment Step 3 Perform Yes No Awake Advanced Techniques* 1 Laryngeal mask exchange 2 Remifentanil technique 3 Airway Exchange Catheter Postpone Tracheostomy Step 4 Post care Recovery / HDU / ICU *Advanced techniques: require training and experience Safe transfer Handover / communication O 2 and airway management Observation and monitoring Analgesia Staffing Equipment Documentation General medical and surgical management Difficult Airway Society Extubation Algorithm 2011 Fig 1 DAS guidelines for the At risk airway. Reproduced from Popat M, Mitchell V, Dravid R, Patel A, Swampillai C, Higgs A. Difficult Airway Society Guidelines for the management of tracheal. Anaesthesia 2012; 67: , with permission from the Association of Anaesthetists of Great Britain & Ireland/Blackwell Publishing Ltd. The dose is dependent on multiple factors and will need to be titrated to effect (too low may result in coughing, too high delayed recovery). A target controlled infusion dose of 1.5 ng ml 1 was shown to reduce haemodynamic changes and coughing in patients undergoing endoscopic sinus surgery. 14 If the infusion is discontinued after, rapid metabolism by non-specific tissue esterases results in a clear wake up with minimum haemodynamic disturbance and return of airway reflexes. However, remifentanil may cause apnoeic episodes and the patient will need close monitoring. Airway exchange catheter/staged There is increasing evidence for the use of airway exchange catheters (AECs) in patients with difficult airways. 15 The AEC is a long hollow bougie that comes in several sizes and can be placed into the trachea through the tracheal tube. The tracheal tube is then removed and the AEC left in the airway with the tip at the level of the mid trachea. It is important that the catheter remains above the carina, and the recommendation is that it should not be inserted beyond 25 cm in an adult patient. The AEC can then be used in the same way as a bougie to help reintubate the trachea in case of deterioration. The correct position should be documented, and the AEC should be correctly labelled and taped to the patient. A chest X-ray and capnography can be performed to confirm correct placement. It is usually well tolerated by patients and has been used in head and neck surgery in the postoperative recovery unit and on critical care. The AEC can be left in for several hours after and has been tolerated for up to 72 h. 16 In general, it should be kept in until the complications that may lead to re-intubation have been ruled out. 17 It is not advisable to administer oxygen via the AEC because of the risk of barotrauma and/or pneumothorax in the event of any outflow obstruction. A staged set has recently been introduced (Fig. 2). It consists of a wire and catheter system where the wire can be passed through the tracheal tube, which is then removed over it. The wire remains in place and the catheter can be reintroduced over the wire to then facilitate re-insertion of a tracheal tube, if required. There have been reports of its effectiveness as a means to reintubation. 17 Keep asleep and transfer to ITU This may appear to be the safest option; however, there remains a risk of obstruction and displacement of the tracheal tube. This may occur during transfer of the patient or in critical care during interventions such as turning the patient. If the patient has an oral tube with a narrow lumen or acutely angled nasal tube, suctioning may prove difficult. This can allow a build-up of secretions and eventual obstruction. These issues should be anticipated before transfer from theatre and, where possible, the tube exchanged to a larger (and preferably) oral tube. While this can be a potentially hazardous procedure, it is important to use the expertise of the theatre team rather than risk tube blockage or displacement on the critical care unit. The patient should be nursed head up and a positive fluid balance avoided to prevent accumulation of fluid in inflamed tissues. 238 BJA Education Volume 17, Number 7, 2017

5 Fig 2 Staged equipment (guide wire, catheter and securing device). Permission for use granted by Cook Medical, Bloomington, Indiana. The depth of the tracheal tube should be assessed and documented regularly; the position should be checked on chest X- ray and under direct vision if there is a concern about tube migration. Humidification of gases and capnography is now routine on critical care and should be used whilst the patient is intubated. The cuff pressure should be tested to ensure excessive pressure is not applied to the tracheal mucosa. The use of deep sedation and muscle relaxation should also be considered. A clear action plan is essential in case difficulties are encountered (this may involve transferring the patient to theatre where a more complete range of options is available). Tracheostomy The decision to perform a tracheostomy will depend on the need for longer-term airway protection, but may also have been performed if tracheal intubation has failed or has been deemed too hazardous. The problems of displacement and obstruction are the same as for a tracheal tube. There should be a clear bedhead sign to identify whether the airway is a temporary tracheostomy or laryngectomy. There are clear guidelines for emergency tracheostomy management in both cases. 18 The type of tracheostomy should also be identified (Slit, Bjork flap or percutaneous). For elective maxilla-facial surgery, the decision to perform a temporary tracheostomy or alternatively overnight intubation is contentious and will usually depend on local practice. Postoperative airway problems Post stridor The most common cause for immediate stridor Post is oedema from trauma to the airway. This can be managed by sitting the patient up, giving nebulized epinephrine and i.v. steroids a dose of 5 mg dexamethasone before has been shown to reduce laryngeal oedema. 19 If there is a concern that the airway is deteriorating then a surgical cause must be ruled out (this includes blood clot or retained throat pack), which may require an examination of the airway under anaesthesia. Laryngeal compromise Laryngeal compromise is caused by oedema and malfunction of the glottis and may be an indication of impending airway obstruction 20 (Fig. 3). It is seen in patients who have had surgical drainage of dental abscesses and Ludwig s angina. It can be a subtle sign, such as a postoperative sore throat which may then progress to deterioration in voice quality (soft, hoarse or barking in nature), poor cough, pain, and difficulty swallowing, finally resulting in stridor and orthopnoea, which are likely to be associated with a difficult tracheal intubation. The key to successful management of these patients is close monitoring and early intervention. There should be senior anaesthetist involvement because any delay may result in the need for advanced airway techniques (e.g. fibreoptic intubation). Bleeding Major bleeding (e.g. carotid blow out) or rapidly expanding haematoma will, in most instances, require urgent intervention. The removal of surgical skin clips may help improve a rapidly deteriorating airway. The patient will need to be transferred to theatre, and a small tracheal tube may be needed to re-intubate because of airway oedema. Valsalva manoeuvres should be avoided in at risk patients (e.g. radical neck dissection). Obstructed tracheal tube/tracheostomy The presence of a tracheal tube or tracheostomy does not prevent problems with the airway from occurring. The use of regular suctioning and humidified oxygen may help prevent secretions from building up. If there is a concern that the tube is obstructed or dislodged then expert help should be immediately sought and the documented action plan activated with early involvement of the surgical team. BJA Education Volume 17, Number 7,

6 Mechanism Laryngeal compromise symptoms/signs Management Sore throat Close observation in a high dependency area Oedema/inflammation of the glottis region causing poor vocal cord function Sore throat + change in voice (soft, hoarse, or barking in nature) Consider tracheal intubation Increasing oedema/inflammation of the glottis region causing poor vocal cord function Sore throat + change in voice + poor cough Tracheal intubation recommended Severe displacement and malfunctioning of the tongue during swallowing; oedema/inflammation of the glottic region with poor vocal cord adduction and epiglottic movement during swallowing Sore throat + change in voice + poor cough + pain and/or difficulty in swallowing Tracheal intubation now critical and likely to be very difficult Severe airway compromise from supraglottic and glottic oedema Sore throat + change in voice + poor cough + drooling + stridor + orthopnoea Tracheal intubation likely to very difficult + emergency surgical airway needs to be considered as well Fig 3 Signs and symptoms of laryngeal compromise with suggested clinical management. Reproduced from Anaesthesia and Intensive care with the kind permission of the Australian Society of Anaesthetists. 20 Post obstructive pulmonary oedema This occurs most commonly at the end of surgery when the patient attempts to breath against a closed airway (e.g. biting on tracheal tube). The negative intrathoracic pressures generated can cause pulmonary oedema and further hypoxaemia. The use of airway adjunct and bite blocks reduces this risk. Treatment is based on relieving the cause of the obstruction (this may include deflating the tracheal tube cuff so that the patient can breathe around it). The use of CPAP may help; however, reintubation must not be delayed if there is significant hypoxia. If the patient is managed with early re-intubation and ventilation then a full recovery is likely. The incidence is higher in muscular patients where very high negative pressure can be generated. Laryngospasm This usually occurs because of stimulation during a light plane of anaesthesia but may also occur because of blood, secretions, and foreign bodies (e.g. retained throat pack). The treatment includes opening and clearing the oropharynx, applying CPAP with 100% oxygen, followed by deepening of anaesthesia usually with an i.v. anaesthetic agent. The use of a short-acting muscle relaxant such as succinylcholine may also be required. If significant laryngospasm occurs, then re-intubation should be considered. Mediastinitis The risk of mediastinitis is high in patients who have Ludwig s angina and deeper infection of the airway. The high mortality associated with mediastinitis warrants an elevated index of suspicion. The clinical picture is one of deep airway infection (stridor, dysphagia, neck rigidity) with systemic toxicity and sub-sternal chest pain. The early use of MRI postsurgery will help target surgical treatment/intervention. Management of the difficult airway on ITU The majority of patients with head and neck pathology where there is serious concern about the postoperative airway will be 240 BJA Education Volume 17, Number 7, 2017

7 managed on the ICU. The key to successful management is good communication between all members of the multidisciplinary team. There should be a clear verbal and written handover. Key points to communicate include: a description of the problem and how it was managed; surgical and anaesthetic interventions that may have affected the airway; the current state of the airway; ongoing management plan; and importantly, who to call if the airway deteriorates. The use of bed-head signs with suggested airway management and the availability of difficult airway equipment are essential. The decision on whether to manage postoperative difficult airway interventions on the ICU or in theatre will depend on the clinical problem, equipment available, the urgency of the situation, the expertise available, and the relative proximity to theatres. When possible, consideration should be given to transferral of the patient to theatre where an airway strategy can more easily be deployed with trained support staff and equipment ready to hand. Declaration of interest None declared. MCQs The associated MCQs (to support CME/CPD activity) can be accessed at by subscribers to BJA Education. References 1. Frerk C, Mitchell V, McNarry A et al. Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults. Br J Anaesth 2015; 115: Gleeson S, Groom P, Mercer S. Human factors in complex airway management. BJA Education 2015; 16: Cook TM, Woodall N, Frerk C. Major complications of airway management in the UK: results of the 4th National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Br J Anaesth 2011; 106: Peterson GN, Domino KB, Caplan RA, Posner KL, Lee LA, Cheney FW. Management of the difficult airway: a closed claims analysis. Anesthesiology 2005; 103: Popat M, Mitchell V, Dravid R, Patel A, Swampillai C, Higgs A. Difficult Airway Society Guidelines for the management of tracheal. Anaesthesia 2012; 67: Patel A. Facemask ventilation before or after neuromuscular blocking drugs: where are we now? Anaesthesia 2014; 69: Checketts MR, Alladi R, Ferguson K et al. Recommendations for standards of monitoring during anaesthesia and recovery 2015: Association of Anaesthetists of Great Britain and Ireland. Anaesthesia 2016; 71: Miller RL, Cole RP. Association between reduced cuff leak volume and post stridor. Chest 1996; 110: Ochoa ME, Marın Mdel C, Frutos-Vivar F et al. Cuff-leak test for the diagnosis of upper airway obstruction in adults: a systematic review and meta-analysis. Intensive Care Med 2009; 35: Pluijms WA, van Mook WN, Wittekamp BH, Bergmans DC. Post laryngeal edema and stridor resulting in respiratory failure in critically ill adult patients: updated review. Crit Care 2015; 19: MacDonnell SP, Timmins AC, Watson JD. Adrenaline administered via a nebulizer in adult patients with upper airway obstruction. Anaesthesia 1995; 50: Patel A, Nouraei SA. Transnasal Humidified Rapid- Insufflation Ventilatory Exchange (THRIVE): a physiological method of increasing apnoea time in patients with difficult airways. Anaesthesia 2015; 70: Spoletini G, Garpestad E, Hill NS. High-flow nasal oxygen or non-invasive ventilation for post hypoxemia. Flow vs Pressure? [Editorial]. JAMA 2016; 315: Nho JS, Lee SY, Kang JM et al. Effects of maintaining a remifentanil infusion on the recovery profiles during emergence from anaesthesia and tracheal. Br J Anaesth 2009; Dec; 103: Mort TC. Continuous airway access for the difficult : the efficacy of the airway exchange catheter. Anesth Analg 2007; 105: Cooper RM. The use of an endotracheal ventilation catheter in the management of difficult s. Can J Anaesth 1996; 43: Corso RM, Cattano D, Maitan S. Experience using a new staged kit in patients with a known difficult airway. Anaesth Intensive Care 2015; 43: McGrath BA, Bates L, Atkinson D, Moore JA. Multidisciplinary guidelines for the management of tracheostomy and laryngectomy airway emergencies. Anaesthesia 2012; 67: Lee CH, Peng MJ, Wu CL. Dexamethasone to prevent post airway obstruction in adults: a prospective, randomized, double-blind, placebo-controlled study. Crit Care 2007; 11: R Greenland KB, Acott C, Segal R, Riley RH, Merry AF. Delayed airway compromise following of adult patients who required surgical drainage of Ludwig s angina: comment on three coronial cases. Anaesth Intensive Care 2011; 39: BJA Education Volume 17, Number 7,