Imran Ahmad

Optimizing oxygenation and intubation conditions during awake fibre-optic intubation using a high-flow nasal oxygen-delivery system

BACKGROUND Awake fibre-optic intubation is a widely practised technique for anticipated difficult airway management. Despite the administration of supplemental oxygen during the procedure, patients are still at risk of hypoxia because of the effects of sedation, local anaesthesia, procedural complications, and the presence of co-morbidities. Traditionally used oxygen-delivery devices are low flow, and most do not have a sufficient reservoir or allow adequate fresh gas flow to meet the patients peak inspiratory flow rate, nor provide an adequate fractional inspired oxygen concentration to prevent desaturation should complications arise. METHODS A prospective observational study was conducted using a high-flow humidified transnasal oxygen-delivery system during awake fibre-optic intubation in 50 patients with anticipated difficult airways. RESULTS There were no episodes of desaturation or hypercapnia using the high-flow system, and in all patients the oxygen saturation improved above baseline values, despite one instance of apnoea resulting from over-sedation. All patients reported a comfortable experience using the device. CONCLUSIONS The high-flow nasal oxygen-delivery system improves oxygenation saturation, decreases the risk of desaturation during the procedure, and potentially, optimizes conditions for awake fibre-optic intubation. The soft nasal cannulae uniquely allow continuous oxygenation and simultaneous passage of the fibrescope and tracheal tube. The safety of the procedure may be increased, because any obstruction, hypoventilation, or periods of apnoea that may arise may be tolerated for longer, allowing more time to achieve ventilation in an optimally oxygenated patient.

A prospective cohort study of awake fibreoptic intubation practice at a tertiary centre

Contemporary data are lacking for procedural practice, training provision and outcomes for awake fibreoptic intubation in the UK. We performed a prospective cohort study of awake fibreoptic intubations at a tertiary centre to assess current practice. Data from 600 elective or emergency awake fibreoptic intubations were collected to include information on patient and operator demographics, technical performance and complications. This comprised 1.71% of patients presenting for surgery requiring a general anaesthetic, with the majority occurring in patients presenting for head and neck surgery. The most common indication was reduced mouth opening (26.8%), followed by previous airway surgery or head and neck radiotherapy (22.5% each). Only five awake fibreoptic intubations were performed with no sedation, but the most common sedative technique was combined target‐controlled infusions of remifentanil and propofol. Oxygenation was achieved with high‐flow, heated and humidified oxygen via nasal cannula in 49.0% of patients. Most operators had performed awake fibreoptic intubation more than 20 times previously, but trainees were the primary operator in 78.6% of awake fibreoptic intubations, of which 86.8% were directly supervised by a consultant. The failure rate was 1.0%, and 11.0% of awake fibreoptic intubations were complicated, most commonly by multiple attempts (4.2%), over‐sedation (2.2%) or desaturation (1.5%). The only significant association with complications was the number of previous awake fibreoptic intubations performed, with fewer complications occurring in the hands of operators with more awake fibreoptic intubation experience. Our data demonstrate that awake fibreoptic intubation is a safe procedure with a high success rate. Institutional awake fibreoptic intubation training can both develop and maintain trainee competence in performing awake fibreoptic intubation, with a similar incidence of complications and success compared with consultants.

Intra-oral ignition of monopolar diathermy during transnasal humidified rapid-insufflation ventilatory exchange (THRIVE)

We present the case of unanticipated airway ignition during hard palate biopsy. Transnasal humidified rapid‐insufflation ventilatory exchange (THRIVE) and monopolar diathermy were utilised for the procedure, during which an arc arose from the diathermy tip to a titanium implant, causing a brief ignition on the monopolar diathermy grip. This case highlights the need for maintained awareness of fire risk when using diathermy in the presence of THRIVE during airway surgery.

Elective use of the Ventrain for upper airway obstruction during high-frequency jet ventilation.

The safety of high pressure source ventilation (jet ventilation) is dependent upon upper airway patency to facilitate adequate passive expiration and prevent increasing intrathoracic pressure and its associated deleterious sequelae. Distortions in airway anatomy may make passive expiration inadequate or impossible in some patients. We report the elective use of the Ventrain device to provide ventilation in a clinical setting of upper airway obstruction in a patient with post radiation fibrosis that had previously prevented passive expiration during attempted high pressure source ventilation.

Fibreoptic tracheal intubation training using bronchoscopy simulation.

The fourth aspect is that in our study, we used ‘dental clicks’ on the manikin as the only available, objective surrogate measure of dental trauma. We do agree with the statement that manikin studies have inherent limitations, namely that the anatomy of manikins is not directly transferable to patients, with the implication that the results must be interpreted cautiously. With this in mind, we welcome future clinical studies investigating suitable techniques for difficult airway management. However, we respectfully disagree with the authors that dental damage is impossible during the insertion and placement of the Berman airway. We are experiencing an increasing geriatric population requiring anaesthesia for a variety of surgical procedures, wherein some patients present themselves with fragile teeth, which are more or less easily damaged – even during the insertion of oral airways.

Enhancing airway assessment of patients with head and neck pathology using virtual endoscopy

Studies have demonstrated that poor assessment and planning contribute to airway complications and that current airway assessment strategies have a poor diagnostic accuracy in predicting difficult intubation in the general population. Patients with head and neck pathology are at higher risk for difficulties during airway management and are more likely to need emergency surgical access. Therefore, thorough assessment of this group of patients is mandatory. The addition of virtual endoscopy (VE) to clinical history and computerised tomography imaging has been shown to improve diagnostic accuracy for supraglottic, glottic and infraglottic lesions and has a positive influence in formulating a more cautious and thorough airway management strategy in this high-risk group of patients. This article reviews whether VE can enhance airway assessment in patients with head and neck pathology and help reduce airway complications.

Current practice for awake fibreoptic intubation – asking the right questions

We would like to thank Drs. Murphy and Howes for their thoughtful editorial, which accompanied our recent study of awake fibreoptic intubation (AFOI) practice [1, 2], and for recognising the training opportunities that our institution provides. However, rather than alluding to unanswered questions in our data, we are concerned that they have applied conjecture and inference to ask the wrong questions about AFOI. Murphy and Howes assert that ‘placing particular emphasis on any individual component . . . risks losing sight of the bigger picture’. Just as pilots emphasise training on the most critical phases of flight, so too must clinicians. Efforts must be made to train for complex, procedural skills as well as considering the important, but non-specific, ‘bigger picture’. The question is – how can we excel at all components of the airway management pathway? The simple answer is self-evident in our data: training. Murphy and Howes cite an editorial [3] written by one of our authors. Our prospective study (rather than audit, as there are no accepted standards) has demonstrated that AFOI is associated with low morbidity and a high success rate, particularly when appropriate training is undertaken. Although we do not state that AFOI should be the ‘gold standard’, our data clearly highlights that AFOI has a valuable role to play in the management of the difficult airway. Had Drs. Murphy and Howes put Ahmad and Bailey’s editorial into context [3], they would have understood that training is recommended for AFOI, and when not undertaken, AFOI should be considered a specialist skill. Performed by appropriately trained and competent clinicians, the utility of a technique that has been part of anaesthetic practice for 50 years is difficult to refute. The question here, then, is: who should train in AFOI? We thank the authors for contextualising our prospective data with retrospective results collected in the USA [4] and Canada [5]. Retrospective data points can be under-reported, and the low complication rates reported by Joseph et al. [4] could be an inaccurate representation of their true incidence. Moreover, the comparable complication rates provided by Law et al. [5] might also be underreported. It would be interesting to know what prospective data from North America shows. Comparing our results with data from unsedated, healthy course delegates (a self-selected group of subjects) is misleading [6]. The immediate complication rate in healthy volunteers was greater than we found in comorbid patients with complex airway pathology (19.5% vs. 11% respectively), and so the co-administration of sedation does not necessarily correlate with increased risk. Interestingly, the Difficult Airway Society has recently commissioned national guidelines on the performance of AFOI. Whether sedation will be recommended as standard practice remains to be seen. The question that needs answering here is: does sedation increase or decrease the safety of performing AFOI? We agree that there is insufficient evidence recommending highflow nasal oxygen (HFNO) for all AFOIs. Murphy and Howes infer our data do not demonstrate that

Elective Use of the Ventrain for Upper Airway Obstruction during HighFrequency Jet Ventilation

The success of high pressure source ventilation is entirely dependent upon upper airway patency to facilitate passive expiration and prevent increasing intrathoracic pressure and its associated deleterious sequelae. Distortions in airway anatomy may make passive expiration inadequate or impossible in some patients.

Comprehensive Dynamic Airway Assessment: Audit of a Novel Technique to Improve Rates of Tracheostomy Decannulation

Objectives: Prolonged tracheostomy is associated with morbidity, mortality, and length of stay. Otolaryngologists are called upon to diagnose and manage patients who have failed to achieve decannulation through conventional protocols. Flexible nasendoscopy (FNE) is commonly used but examines only the supraglottic airway. The comprehensive dynamic airway assessment (CDAA) extrapolates the principles of awake fiber-optic intubation, allowing a complete upper airway assessment, including the subglottis with decannulation under direct vision, if appropriate. Methods: A two-cycle audit was performed on patients discharged from the intensive care unit with tracheostomy in situ. A retrospective 25 month audit of decannulation rates was performed to assess conventional management with ear, nose, and throat (ENT) review and standard FNE in cases that failed to achieve decannulation due to airflow problems. A prospective 8 month audit was then undertaken after the inception of CDAA. Results: Using conventional management, the number of patients discharged from intensive care unit (ICU) with tracheostomy in situ was 137, of which 17 failed to decannulate through protocol management alone. Five (31%) patients were eventually decannulated using a standard approach. After inception of CDAA, 76 were discharged from ICU. Eight underwent CDAA, of whom 6 (75%) were decannulated; a diagnosis for decannulation failure was made in the remaining 2 patients. Conclusions: CDAA is an essential diagnostic tool that can improve outcomes for complex patients with tracheostomies. It requires minimal resource, is versatile, and is a natural extension of the expert nasendoscopic skills of the otolaryngologist. CDAA should form an integral part of all decannulation protocols.