Difficult airway prediction using ultrasound in morbidly obese patients

DIFFICULT AIRWAY PREDICTION USING ULTRASOUND IN MORBIDLY OBESE PATIENTS Obesity is a common health problem today. With the increase in obesity, the frequency of encounters with these patients during surgery also increases every day. Obese patients may have difficulty providing an airway during anesthesia due to factors such as excessive accumulation of adipose tissue in the neck, face circumference, tongue, palate and pharynx, and neck circumference width. Currently, ultrasonography (USG) can be used as a potential scanning tool for the difficult airway. The aim of this study was to investigate the contribution and availability of anterior neck soft tissue thickness (ANS), tongue volume (DH), hyomental distance (HMD) and hyomental distance ratio (HMDR), the ratio of pre-epiglottic distance and distance between epiglottis and the midpoint of vocal cords (PE/E-VC) to difficult airway estimation in morbidly obese patients. After approval of the Ethics Committee and written consent from patients, obese patients who underwent endotracheal intubation under general anesthesia, in the sniffing position, who would undergo elective surgery, ≥18 years of age, body mass index (BMI) ≥40 kg/m2, ASA III-IV risk class were evaluated. In preoperative evaluation of patients, demographic characteristics, Mallampati classification, BMI, mouth opening, thyromental and sternomental distance, neck circumference, presence of movement restriction in neck and DH, ANS thickness, HMD and HMDR, PE/E-VC ratio using USG were measured and recorded. All patients had difficulty in ventilation with a mask after endotracheal intubation, Cormack-Lehane (C-L) grade and intubation difficulty scale (EZS) were recorded. Difficult intubation evaluation was performed using the Cormack-Lehane classification system. In the receiver operating characteristic (ROC) analysis, a statistically significant relationship was determined between the difficult mask ventilation and DH (>85203.67 ml3, p<0.001), ANS-thyrohyoid (>22.6 mm, p<0.001), ANS-thyroid isthmus (>9.8 mm, p = 0.002) and ANS-suprasternal notch thickness (>9.9 mm, p = 0.004) and PE/E-VC (>1.86, p = 0.005). In the ROC analysis, a statistically significant relationship was determined between the difficult intubation and ANS thickness at the level of the thyrohyoid membrane (>19.9 mm, p<0.001) and PE/E-VC (>2, p<0.001). In conclusion, we found that tongue volume, anterior neck soft tissue thickness measured at the levels of thyrohyoid membrane, thyroid isthmus and suprasternal notch and PE/E-VC ratio measured by USG were successful for predicting difficult mask ventilation. And we found the anterior neck soft tissue thickness measured at the levels of thyrohyoid membrane and PE/E-VC ratio measured by USG were successful for predicting difficult mask ventilation. We think that preepiglottic anterior neck soft tissue thickness measured at level of the thyrohyoid membrane and PE/E-VC parameters measured by ultrasound in the morbid obese patients can be used as criteria for predicting difficult airway. Keywords: Morbid obesity, difficult airway, ultrasonography