Comparative Study between two Ultrasound Aided Methods in PreoperativeAssessment of Difficult Airway in Obese Patients

Abstract

Abstract Background Unpredictable difficult laryngoscopy remains a challenge for anaesthesiologists, especially if difficult ventilation occurs. So, accurate airway assessment should always be performed so as to provide appropriate planning and management of expected difficult intubation and to limit any unexpected difficulties. Airway assessment using ultrasound has been proposed recently as a useful, simple and non-invasive bed side tool as an adjunct to clinical methods. Objective To establish whether correlations existed between two ultrasound measurements and the Cormack–Lehane grade during direct laryngoscopy, and whether these measurements are useful in predicting are stricted or difficult view especially in morbid obese individuals. The first is the measurement of the hyomental distance of the patient in neutral position of the neck and in fully extended neck calculating the ratio between both of them. While the second is the measurement of anterior cervical soft tissue thickness at three anatomical levels (hyoid bone, thyrohyoid membrane or ‘pre epiglottic space’ and anterior commissure). We chose these two new measurements from among the various ultrasound assessments made in previous studies because of their simplicity of execution in normal clinical and in emergency settings. Patients and Methods The current study is a prospective comparative clinical trial of assessment of difficult air way using two different ultrasound aided techniques in comparison to Cormack and lehane scoring system. Those patients were chosen upon some inclusion and exclusion criteria; inclusion criteria were (Age of the patient (25-60y), ASA I-II patients, Obese patients with body mass index > 30 kg /m2 and Pts undergoing bariatric surgery) and exclusion criteria were (Pathology of the airway (tumors), Deformity of the airway anatomy (burns, scars), History of facial, cervical, pharyngeal and epiglottis surgery or trauma, Patients with most teeth lost and Patient refusal). Results Regarding U/S measurements in method A patients; the average HMD-neutral of A patients was (53.58±5.33) mm, the average HMD-extension was (58±7.82) mm, and the average HMDR was (1.07±0.06). It showed highly significant decrease in HMD extension and HMDR in difficult group, compared to easy group, in A group of patients (p < 0.01respectively). Non-significant difference as regards HMD-neutral U/S measurements in method A (p > 0.05). Conclusion Ultrasonography can be a valuable adjunct in this aspect of airway assessment. Ultrasound assessment of pre-epiglottic tissue thickness at the level of the thyrohyoid membrane may be useful to predict restricted/difficult direct laryngoscopy and difficult intubation. The ratio of hyomental distance between neutral and extended positions may also be a good predictor of difficult direct laryngoscopy.