Accuracy of airway ultrasonic parameters in predicting difficult mask ventilation in obese patients / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the accuracy of airway ultrasonic parameters in predicting difficult mask ventilation (DMV) in obese patients.Methods:Ninety-six patients of both sexes, aged >18 yr, with body mass index of 28- <40 kg/m 2, of American Society of Anesthesiologists Physical Status classification Ⅰ or Ⅱ, scheduled for elective surgery under general anesthesia with endotracheal intubation, were selected. The airway was evaluated at 1 day before surgery to record the thyromental distance, modified Mallampati classification and upper lip bite test classification. Before anesthesia induction, the mandibular condylar motion, longitudinal cross-sectional area and transverse diameter of the tongue were measured by ultrasound, and the tongue volume was calculated. Mask ventilation was performed after anesthesia induction, DMV classification was recorded, DMV was defined as DMV classification Ⅲ and Ⅳ, and the patients were divided into non-DMV group (NDMV group) and DMV group. Spearman correlation analysis was used to analyze the correlation between each parameter and DMV, the receiver operating characteristic (ROC) curve was used to evaluate the accuracy of each parameter in predicting DMV, and the cut-off value was determined based on the principle of Jorden index at maximum. Results:Ninety-six patients were finally included in the study, with 64 patients in NDMV group and 32 patients in DMV group. Compared with NDMV group, the increase in age, modified Mallampati grade, upper lip biting test grade, longitudinal cross-sectional area of tongue, transverse diameter of tongue and volume of tongue were significantly increased, and the thyromental distance and mandibular condylar motion were decreased in DMV group ( P<0.05). Age ( r=0.283), modified Mallampati grade ( r=0.668), upper lip biting test classification ( r=0.826), tongue longitudinal cross-sectional area ( r=0.598), tongue transverse diameter ( r=0.578) and tongue volume ( r=0.707) were positively correlated with DMV ( P<0.01), and thyromental distance ( r=-0.623) and mandibular condylar motion ( r=-0.666 ) were negatively correlated with DMV ( P<0.05). The area under curve (95% confidence interval) of tongue longitudinal cross-sectional area, tongue transverse diameter, tongue volume, and mandibular condylar motion for DMV prediction were 0.870 (0.780-0.961), 0.858 (0.768-0.948), 0.937 (0.864-1.000), 0.912 (0.835-0.990), respectively ( P<0.01), and the predicted cut-off values were 22.61 cm 2, 4.29 cm, 100.60 cm 3 and 1.18 cm, respectively, the sensitivity was 90%, 83%, 90% and 90%, respectively, the specificity was 80%, 80%, 95% and 95%, respectively. Conclusions:Tongue volume and mandibular condylar motion measured by ultrasound are highly accurate in predicting DMV in obese patients. Tongue volume> 100.60 cm 3 or mandibular condylar motion< 1.18 cm suggests a high risk of DMV.