|Year : 2019 | Volume
| Issue : 2 | Page : 55-56
Airway assessment by ultrasonography: Is it the final answer?
Arindam Choudhury, Rohan Magoon
Department of Cardiac Anaesthesia, C. N. Centre, AIIMS, New Delhi, India
|Date of Web Publication||28-Aug-2019|
Dr. Arindam Choudhury
Additional Professor, Department of Cardiac Anaesthesia, C. N. Centre, AIIMS, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Choudhury A, Magoon R. Airway assessment by ultrasonography: Is it the final answer?. Airway 2019;2:55-6
Preoperative airway assessment is largely aimed at predicting poor laryngoscopic views as assessed classically by Cormack and Lehane (CL) grading system. However, lack of concurrence between any single traditional airway assessment parameter and direct laryngoscopy prompted anaesthesiologists to employ multipronged airway evaluation tests for prediction of a difficult airway (DA). Recently, ultrasonography (USG) is being increasingly employed for airway assessment. The ubiquitous presence of an ultrasound machine has almost established it as a point-of-care testing tool.
USG has been employed reliably for a decade now for confirming endotracheal/endobronchial intubation. As perioperative physicians become increasingly acquainted with airway ultrasound, they have begun evaluating the value of ultrasound in accurately predicting DA. Essentially, USG relies upon assessment of the soft tissues surrounding the airways in terms of their depth, dimensions, volumes and mobility, whereas an adequate laryngoscopy gives us a direct assessment of the glottis with our own visual inputs.
In this issue, Narula and Nasser have addressed ultrasound-based prediction of difficult laryngoscopic grade in the Indian subpopulation. They studied parameters such as pre-epiglottic space, distance from epiglottis to midpoint of vestibular ligaments, distance from skin to the hyoid bone and distance from skin to epiglottis midway between hyoid bone and the thyroid cartilage. Although none of the parameters reached statistical significance to reveal a strong correlation for poor CL grade, they constitute a significant step forward towards the inclusion of USG in the armamentarium of airway assessment.
The above study revealed that only 24% of the total patients demonstrated difficult laryngoscopic view (CL Grade 3 and more) while they were scheduled for elective surgery. In fact, all the high-risk conditions for difficult laryngoscopy and intubation were eliminated in this study. On the contrary, we should have studies involving high-risk groups to test the prowess of USG as a tool to predict poorer views a priori because we need bigger numbers for greater sensitivity and to improve test specificity.
Despite being an active area of research, USG-based airway assessment has certain caveats that need to be remembered always. The first and foremost are the concerns such as intra- and interobserver variability and often unpredictable artefacts. Moreover, lack of tailor-made probes as well as formal training also present peculiar impediments. Finally, we continue to be in search of those robust USG parameters that would best predict difficult laryngoscopic views.
The present emphasis is on validating the role of USG-based dimensions for an improved predictability of difficult laryngoscopy, adding new depth and breadth to USG-based airway assessment. The fraternity eagerly awaits more focused research in this area of widespread clinical interest.
| References|| |
Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984;39:1105-11.
Kundra P, Mishra SK, Ramesh A. Ultrasound of the airway. Indian J Anaesth 2011;55:456-62.
] [Full text]
Narula GK, Nasser A. Correlation between ultrasonographic evaluation of the airway and Cormack-Lehane view by direct laryngoscopy in the Indian subpopulation. Airway 2019;2:71-6. [Full text]
Myles PS, Gin T. Statistical Methods for Anaesthesia and Intensive Care. 1st
ed. Oxford: Butterworth-Heinemann; 2000.