Diagnostic Value of Neck Circumference and Sternomental Distance for Difficult Intubation in Patients Undergoing Cesarean Section

Airway safety for difficult intubation or failure to intubate is important during anesthesia. This study assessed the airway before anesthesia, and the diagnostic value of neck circumference (NC) and sternomental distance (SMD) tests was investigated in predicting difficult tracheal intubation during cesarean section. In a cross-sectional study, 101 women who were candidates for cesarean section were selected through the convenience and non-random sampling method. The modified Mallampati test (MMT), upper lip bite (ULBT), thyromental distance (TMD), neck circumference (NC), and sternomental distance (SMD) tests were performed to estimate the laryngoscopy problem. The success rate of airway assessment by SMD and NC was evaluated using the Cormack-Lehane score. Data analysis was performed using the software SPSS version 16.0. TMD (p=0.034) and NC (p<0.001) indicated substantial association with laryngoscopy grades. The sensitivity was 35.29% and 58.82%, and the specificity was 93.93% and 59.09% for NC and SMD. The accuracy, NPV, and PPV of NC was higher than the SMD test (74% vs. 59%, 73.80% vs. 73.58, and 75% vs. 42.55%). The PPV and NPV were 43.63% and 77.77% for TMD. MMT, with high sensitivity (73.52%) and specificity (90.90%), increased the risk of difficult laryngoscopy up to 24-fold when adjusted for TMD, SMD, and NC [p<0.001; OR=24.38 (6.31-94.25)]. Although NC indicated low sensitivity, it had maximum specificity (93.93%) in predicting difficult intubation. High Mallampati grades increase the risk of difficult laryngoscopy. NC presented low predictive values, and SMD and TMD lack predictive values for difficult intubation.