Evaluation of various anthropometric airway parameters as predictors of difficult airway in neonates: A prospective observational study

Objective: To determine the relationship between various anthropometric parameters (age, weight, neck circumference, head circumference, thyromental distance, sternomental distance, frontal plane to chin distance, and frontal plane to chin distance by weight ratio) in neonates with difficult laryngoscopy and difficult intubation. Design: A Prospective, double-blind, observational study. Setting: Conducted in a Tertiary care Hospital in India. The study was conducted over a period of one year. Patients: Participants included 100 neonates undergoing either elective or emergency non-cardiac surgery under general anesthesia. Interventions: The various anthropometric parameters were correlated with Difficult laryngoscopy (Cormack Lehane grading III, IV) and Difficult intubation (Intubation Difficulty score>5). Measurements: Difficult laryngoscopy (Cormack lehane grade III, IV) and Difficult intubation (Intubation Difficulty score >5). Main results: We found a statistically significant difference between weight (2.5 (2.2-2.8) kg vs 1.9 (1.55-2.35) kg), (p = 0.006), TMD (3.03 (2.74-3.46) cm vs 2.70 (2.45-3.13) cm), (p = 0.029), SMD (5.18 (5.06-5.76) cm vs 5.02 (4.84-5.29) cm), (p = 0.020) and FPCD/Wt ratio (0.31 (0.27-0.36) vs 0.44 (0.37-0.44)) with p = 0.001 in neonates with Easy and Difficult laryngoscopy. Using ROC curve analysis we calculated AUC, optimal cut off value, sensitivity, specificity, PPV and NPV for weight, TMD, SMD and FPCD/Wt ratio and found FPCD/Wt ratio to be best predictor for difficult laryngoscopy with highest AUC (0.844), high sensitivity (77.78%) and NPV (97.44%). Conclusions: No single parameter can provide a high index of sensitivity and specificity to predict difficult airway in neonates. Therefore, a combination of tests, including Weight, TMD, SMD, and FPCD/Wt ratio, should be used. To the best of our knowledge, this is the first prospective study to assess predictors to the difficult airway in neonates.