Submental ultrasound for assessment of difficult mask ventilation in patients with obstructive sleep apnoea posted for surgery under general anaesthesia. A prospective observational study

Abstract

Background and aimsUndiagnosed obstructive sleep apnoea (OSA) is commonly encountered in the perioperative setting. The ASA Task Force recognizes OSA as an important risk factor for difficult mask ventilation or intubation, or both. Thus effective mask ventilation plays a pivotal role in safe airway management of these patients. Pre-operative submental ultrasonography (USG) could be an adjunct to conventional anthropometric parameters for prediction of difficult mask ventilation (DMV). The aim of this study is to evaluate the accuracy of USG screening parameters in predicting DMV in patients presenting with undiagnosed OSA in the perioperative period. MethodsThis prospective observational study was conducted in patients undergoing elective surgery in a tertiary care hospital of south India. The study population consisted of undiagnosed and untreated OSA patients with STOP-BANG scores>3 on pre-operative screening. Submental USG was performed to record three parameters; the distance between the lingual arteries (DLA), hyo-mental distance (HMD) and tongue base thickness (TBT). The degree of difficult mask ventilation was recorded by Han's scale. ResultsThe incidence of DMV was 14.96%. The mean of all the three USG parameters (DLA, HMD and TBT) increased according to the DMV level. Logistic regression analysis demonstrated DLA above 30.78 mm was the single most important predictor of DMV (odds ratio 0.030, 95% CI, 0.871–0.990). ConclusionSubmental USG of the airway is a useful diagnostic tool for predicting DMV in OSA patients. DLA is the most sensitive and specific sonographic parameter for screening of difficult mask ventilation in these patients.