Virtual endoscopy—a new assessment tool in difficult airway management

Awake Tracheal Intubation: An Update

Awake tracheal intubation (ATI) remains the "gold standard" technique in securing a definitive airway in conscious, self-ventilating patients with predicted or known difficult airways and the procedure is associated with a low failure rate. Since its inception a variety of techniques to achieve ATI have emerged and there have been accompanying advancements in pharmaceuticals and technology to support the procedure. In recent years there has been a growing focus on the planning, training and human factors involved in performing the procedure. The practice of ATI, does however, remain low around 1% to 2% of all intubations despite an increase in those with head and neck pathology. ATI, therefore, presents a skill that is key for the safety of patients but may not be practised with regularity by many anesthetists. In this article we therefore aim to highlight relevant guidance, recent literature and provide an update on the practical methods fundamental for successful ATI. We also discuss the crucial aspects of a safe airway culture and how this can help to embed training and maintenance of skills.

Innovations in the Management of the Difficult Airway: A Narrative Review

The difficult airway (DA) remains a perpetual challenge and its implications have led to multiple advances, technological and otherwise in this area. This article investigates the latest developments in the definition, prediction tools and diagnostics like airway and neck Ultrasonography (USG), Magnetic Resonance Imaging (MRI) and Computed tomography (CT) scans, preoperative Virtual endoscopy (VE) and 3D printing. Innovations in airway devices and adjuncts are analysed. Difficult airway society (DAS) guidelines, American Society of Anaesthesiologists (ASA) Practice Guidelines and Vortex approach for the management of DA are explored. Other breakthroughs include novel oxygen supplementation techniques throughout airway management and tools like Anaesthesia Information Management Systems (AIMS) and Clinical Decision Support (CDS) systems. The delivery of DA training and patient counselling has also undergone vast changes with emerging technology like Virtual Reality (VR), mobile applications and toolkits. The enormous, ever-evolving and endless possibilities in this area have only helped improve clinical standards and enhance patient safety.

Comparison of diagnostic accuracy of computed tomography virtual endoscopy and flexible fibre-optic laryngoscopy in the evaluation of neck anatomic structures and neoplasms

BACKGROUND AND PURPOSE

Computed tomography virtual endoscopy (CT-VE) is a non-invasive technique which allows visualisation of intraluminal surfaces by tridimensional reconstruction of air/soft tissues. The aim of this study was to compare the diagnostic accuracy of CT-VE and flexible fibre-optic laryngoscopy (FFL) in identifying normal neck anatomic structures and pharyngeal and laryngeal lesions.

METHODS

Forty-two patients with a history of neck cancer were assessed by two ENT surgeons using FFL and by one neuroradiologist using CT-VE in order to evaluate the visualisation of the epiglottis, vallecula, glossoepiglottic folds, pyriform sinuses, vocal cords and mass pathology. The visualisation of the structures in both modalities was assessed according to the following score: 0 = not visualised, 1 = partial visualisation, 2 = complete and clear visualisation. A weighted kappa coefficient was used to evaluate the inter-observer agreement. McNemar's test was performed to compare the two diagnostic tests.

RESULTS

The inter-observer agreement between FFL and CT-VE was fair in the assessment of the vocal cords (k = 0.341); moderate in the assessment of the glossoepiglottic folds (k = 0.418), epiglottis (k = 0.513) and pyriform sinuses (k = 0.477); and substantial in the assessment of the vallecula (k = 0.618) and the tumour (0.740). McNemar's test showed no significant difference between the two tests (p<0.05).

CONCLUSION

CT-VE is a non-invasive technique with a diagnostic accuracy comparable to FFL in terms of visualisation of anatomical structures and pharyngeal and laryngeal lesions.

Difficult airways: a 3D printing study with virtual fibreoptic endoscopy

Head and neck cancer patients present unique airway challenges, and oropharyngeal, laryngeal, and hypopharyngeal tumours considerably distort and narrow the anatomy of the airway. We describe the use of 3D augmented reality software combined with 3D printed models to assess the anatomy of difficult airways and to assist in the formulation of the most optimal airway management strategy in such patients. The reported patients had computed tomograms (CT) of the neck prior to their anaesthetic and surgical management. DICOM files of the respective scans were imported to 3D rendering software (OsiriX, Pixmeo). We constructed volume rendered models for initial assessment of the airway then generated serial surface rendered models to create a virtual endoscopic path of the airway to simulate the fibreoptic approach. To further facilitate the study of difficult airways we have subsequently printed 3D models of those that were most difficult using rapid prototyping. Head and neck tumours significantly distort the airway. Thorough study of the relevant anatomy prior to airway management for operating reasons enhances communication between the surgeon and anaesthetist, and aids selection of the most appropriate intubation approach. In conclusion, this paper highlights a useful and novel pre-assessment strategy that allows a virtual, visual, 3-dimensional assessment of the airway anatomy combined with 3D modelling and 3D printing. This enables the airway specialist, anaesthetist, and head and neck surgeon to anticipate any critical steps and adjust the plan accordingly.

Radiological evaluation of airway - What an anaesthesiologist needs to know!

Airway management forms the foundation of any anaesthetic management. However, unanticipated difficult airway (DA) and its sequelae continue to dread any anaesthesiologist. In spite of development of various clinical parameters to judge DA, no single parameter has proved to be accurate in predicting it. Radiological evaluation may help assess the aspects of patient's airway not visualised through the naked eye. Starting from traditional roentgenogram to ultramodern three-dimensional printing, imaging may assist the anaesthesiologists in predicting DA and formulate plan for its management. Right from predicting DA, it has been used for estimating endotracheal tube sizes, assessing airway pathologies in paediatric patients and planning extubation strategies. This article attempts to provide exhaustive overview on radiological parameters which can be utilised by anaesthesiologists for prediction of DA.

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.

The effect of virtual endoscopy on diagnostic accuracy and airway management strategies in patients with head and neck pathology: a prospective cohort study

PURPOSE

There is growing evidence to suggest a deficiency in anesthesiologists' diagnosis of airway pathology and subsequent airway management planning, and conventional instruments have not shown increases in safety. Virtual endoscopy (VE) is a tool that can detail intraluminal anatomical "fly-through" information in a format visually similar to the flexible endoscopic views familiar to anesthesiologists. We aimed to determine the effect of VE on diagnostic accuracy and airway management strategies when compared with conventional tools.

METHODS

Clinical scenarios, along with computerized tomography (CT) imaging, were presented to 20 anesthesiologists, and structured questions were asked regarding diagnosis of airway pathology and airway management strategy. Virtual endoscopy videos were then provided and the questions were repeated. Following the CT and VE presentations, the anesthesiologists' responses involving diagnostic accuracy and airway management strategy were compared between the CT and VE techniques. Answers relating to the utility of VE were also sought.

RESULTS

Diagnostic accuracy was 54.1% with CT alone and increased to 67.7% when VE was added (P = 0.007). In 48% of cases, the addition of VE to clinical history and CT led to changes in airway management strategy (P < 0.001), and 90.6% of these changes were deemed more cautious (P < 0.001).

CONCLUSION

Virtual endoscopy improves the accuracy in diagnosis of airway pathology when compared with CT alone. Furthermore, it leads to more conservative and potentially safer airway management strategies in patients with head and neck pathology.