Difficult intubation assisted by three-dimensional computed tomography imaging of the pharynx and the larynx

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.

An evaluation of McCoy balloon laryngoscopy in patients with moderate-to-major endotracheal intubation difficulty

We hypothesized that combined McCoy-balloon laryngoscopy may facilitate airway management relative to McCoy or balloon laryngoscopy. In 10 anesthetized/paralyzed patients with prior intubation difficulty scale scores of >5, McCoy-balloon laryngoscopy versus conventional/balloon/McCoy laryngoscopies resulted in greater laryngeal aperture exposure (2.3 +/- 0.6 versus 0.6 +/- 0.2/1.4 +/- 0.4/1.5 +/- 0.6 cm2, respectively), lower intubation difficulty scale score (0.00 (0.00-0.00) versus 6.00 (6.00-8.25)/1.50(0.00-4.00)/2.00(0.75-5.00), respectively, median [interquartile range]), and 9%-74% shorter time to intubation confirmation (P < 0.05-0.001 for all). Balloon and McCoy laryngoscopies improved laryngoscopic/intubating conditions relative to conventional laryngoscopy. In patients with moderate-to-major conventional airway management difficulty, McCoy-balloon laryngoscopy further improves laryngoscopic/intubating conditions.

IMPLICATIONS

This study shows that, in patients with moderate-to-major conventional airway management difficulty, combined McCoy-balloon laryngoscopy results in improved laryngoscopic/intubating conditions when compared with the conventional, McCoy, and balloon laryngoscopic techniques. McCoy-balloon laryngoscopy combines the merits of McCoy and balloon laryngoscopy and can be recommended for patients with moderate-to-major intubation difficulty.

Preoperative airway evaluation using multi-slice three-dimensional computed tomography for a patient with severe tracheal stenosis †

A 71-yr-old female with a malignant thyroid tumour was to undergo thyroidectomy under general anaesthesia. Preoperative chest x-ray and plain computed tomography (CT) showed severe tracheal stenosis. Three-dimensional figures of the trachea and a virtual bronchoscopic movie were obtained from multi-slice CT to evaluate the stenotic region and to simulate fibroscopic tracheal intubation, respectively. After induction of general anaesthesia with propofol, a tracheal tube was successfully passed through the stenotic region under the guide of a fibroscope as simulated in the virtual movie. We conclude that multi-slice CT is useful for preoperative airway evaluation for patients with stenosis and distortion of the trachea.

The utility of three-dimensional computed tomography in unanticipated difficult endotracheal intubation

IMPLICATIONS

We experienced a case of unanticipated difficult intubation with direct laryngoscopy because of narrowing of the retropharyngeal air space and laryngeal vestibulum. It is suggested that three-dimensional computed tomography is useful for evaluating both the abnormality of an airway and its relationship to surrounding tissue.

Predictive models for difficult laryngoscopy and intubation. A clinical, radiologic and three-dimensional computer imaging study

PURPOSE

To identify the variables most useful in predicting difficult laryngoscopy and intubation from various clinical, skeletal (lateral x-rays) and soft tissue (three-dimensional computed tomography imaging) measurements.

METHODS

Twenty-four adult patients in whom an unanticipated difficult tracheal intubation was identified according to established criteria were evaluated. Further, a control group of 32 patients in whom tracheal intubation was easily accomplished was studied. We applied multivariate discriminant analysis to clinical and radiological data of all patients to select those variables most useful in predicting difficult laryngoscopy and intubation. The receiver operating characteristic (ROC) curve was used to describe the discrimination abilities and to explore the trade-offs between sensitivity and specificity of the model.

RESULTS

With the clinical data alone, discriminant analysis identified four risk factors that correlated with the prediction of difficult laryngoscopy and intubation: thyrosternal distance, thyromental distance, neck circumference and Mallampati classification. With both clinical and radiological data, discriminant analysis identified five risk factors: thyrosternal distance, thyromental distance, Mallampati classification, depth of spine C2 and angle A (the most antero-inferior point of the upper central incisor tooth). The positive predictive value of this combined (clinical and radiological) model was greater than that of the clinical model alone (95.8% vs 87.5%, respectively). The areas under the ROC curves, that measure the probability of the correct prediction of the clinical and the combined models, were found to be 0.933 and 0.973, respectively.

CONCLUSIONS

These models can be used for predicting difficult laryngoscopy and intubation in clinical practice.