Predicting difficult laryngoscopy in morbidly obese Thai patients by ultrasound measurement of distance from skin to epiglottis: a prospective observational study.

BACKGROUND: In morbidly obese patients, airway management is challenging since the incidence of difficult intubation is three times than those with a BMI within the healthy range. Standard preoperative airway evaluation may help to predict difficult laryngoscopy. Recent studies have used ultrasonography-measured distance from skin to epiglottis and pretracheal soft tissue at the level of vocal cords, and cut-off points of 27.5 mm and 28 mm respectively have been proposed to predict difficult laryngoscopy. The purpose of this study is to evaluate ultrasonography-measured distance from skin to epiglottis for predicting difficult laryngoscopy in morbidly obese Thai patients. METHODS: This prospective observational study was approved by the Ethics Committee of the Faculty of Medicine, Prince of Songkla University. Data were collected from January 2018 to August 2020. Eighty-eight morbidly obese patients (BMI ≥ 35 kg/m2) requiring general anesthesia with endotracheal intubation for elective surgery were enrolled in the Songklanagarind Hospital. Preoperatively, anesthesiologists or nurse anesthetists who were not involved with intubation evaluated and recorded measurements (body mass index, neck circumference, inter incisor distance, sternomental distance, thyromental distance, modified Mallampati scoring, upper lip bite test, and distance from skin to epiglottis by ultrasound. The laryngoscopic view was graded on the Cormack and Lehane scale. RESULTS: Mean BMI of the eighty-eight patients was 45.3 ± 7.6 kg/m2. The incidence of difficult laryngoscopy was 14.8%. Univariate analysis for difficult laryngoscopy indicated differences in thyromental distance, sternomental distance and the distance from skin to epiglottis by ultrasonography. The median (IQR) of thyromental distance in difficult laryngoscopy was 6.5 (6.3, 8.0) cm compared with 7.5(7.0, 8.0) cm in easy laryngoscopy (p-value 0.03). The median (IQR) of sternomental distance in difficult laryngoscopy was 16.8 (15.2, 18.0) cm compared with 16.0 (14.5, 16.0) cm in easy laryngoscopy (p-value 0.05). The mean distance from skin to epiglottis was 12.2 ± 3.3 mm Mean of distance from skin to epiglottis in difficult laryngoscopy was 12.5 ± 3.3 mm compared with 10.6 ± 2.9 mm in easy laryngoscopy (p-value 0.05). Multivariate logistic regression indicated the following factors associated with difficult laryngoscopy: age more than 43 years (A), thyromental distance more than 68 mm(B) and the distance from skin to epiglottis more than 13 mm(C). The scores to predict difficult laryngoscopy was calculated as 8A + 7B + 6C based on the data from our study. One point is given for A if age was more than 43 years old, 1 point is given for B if thyromental distance was less than 6.8 cm and 1 point is given for C if the distance from skin to epiglottis by ultrasonography was more than 13.0 cm. The maximum predicting score is 21, which indicates a probability of difficult laryngoscopy among our patients of 36.36%, odds 0.57, likelihood ratio 3.29 and area under the ROC curve of 0.77, indicative of a good predictive score. CONCLUSIONS: Age, thyromental distance and ultrasonography for the distance from skin to epiglottis can predict difficult laryngoscopy among obese Thai patients. The predictive score indicates the probability of difficult laryngoscopy.

The evaluation of using new trachea and skin manikins for practicing emergency anterior neck access.

Emergency anterior neck access may be performed if intubation and ventilation fail. Practicing this life-saving procedure with manikins before facing a real-life emergency anterior neck access is required to do this procedure successfully when we encounter a difficult airway situation. The current manikins are expensive and thus are sometimes difficult to acquire in low-cost settings such as Thailand. We devise a cost-effective training manikin using less expensive materials but retaining the simple design of the trachea and skin areas which are flexible polyurethane (PU) foam and silicone, but which still had the same utility as the current manikins. Five items were evaluated, and then scores were rated by experienced physicians from 1 to 5 points for each item, 1 being the least and 5 the highest. The mean score concerning the appropriate size of the manikins was 4.55 ± 0.56. The mean score of the ease of use for practicing was 4.58 ± 0.59. The mean score of the similarity of the skin of the manikins to human skin was 3.85 ± 0.66. The mean score of the similarity of the trachea of the manikins to the human trachea was 3.80 ± 0.69. The mean score of the sensation of inserting the tube in the manikin compared to a real trachea was 3.90 ± 0.67. The mean overall benefit score of practicing on the manikins was 4.38 ± 0.45. Our trial indicates that this low-cost and simply designed manikin can be useful for practicing emergency airway management procedures to save patients who are struggling with lack of oxygen or intubation failure or failure of ventilation or other airway equipment such as endotracheal intubation and supraglottic airway devices (SGA).