Value of ultrasound-measured quantification of anterior neck soft tissue in predicting difficult laryngoscopy in obese patients

Abstract

Objective To evaluate the value of ultrasound-measured quantification of anterior neck soft tissue in predicting the difficult laryngoscopy in the obese patients. Methods Ninety-six patients, with body mass index ≥ 28 kg/m2, aged 22-60 yr, of ASA physical status Ⅰ or Ⅱ, scheduled for elective surgery under general anesthesia with endotracheal intubation, were selected.Assessment methods of modified Mallampati grade (method M) and anterior neck soft tissue quantification measured by ultrasound (method U) were performed before anesthesia.The level of vocal cords was selected using ultrasound scanning for anterior neck.The positive result was greater than 20 mm in method U, and was grade Ⅲ or Ⅳ in method M. Direct laryngoscope was placed after induction of anesthesia.Difficult laryngoscopy was defined as Cormack-Lehane grade Ⅲ or Ⅳ, or in whom laryngoscope could not be placed.The sensitivity, specificity and accuracy of the two assessment methods for predicting the difficult laryngoscopy were calculated. Results Twenty-two patients were found to have difficult laryngoscopy, and the anterior neck soft tissue quantification was (23.0±3.0) mm, which was significantly thicker than that in the patients of non-difficult laryngoscopy ((1.9±2.2) mm). The sensitivity, specificity and accuracy of method U were 91%, 92% and 92%, respectively, and of method M were 77%, 81% and 80%, respectively, and there was significant difference between the two methods.There was no significant difference in the parameters of difficult laryngoscopy which were predicted using method U between the patients of different ages or gender. Conclusion It can accurately predict the difficult laryngoscopy in the obese patients when the ultrasound-measured quantification of anterior neck soft tissue is greater than 20 mm. Key words: Skinfold thickness; Ultrasonography; Laryngoscopy; Obesity; Forecasting