Background and Aim: The overall incidence of difficult laryngoscopy in pediatric anesthesia is lower than in adults, but this risk is higher in patients younger than one year of age. In the last decade, different measurements have been used to obtain difficult laryngoscopy markers in children. In this study, we aimed to evaluate the relationship between the airway measurements (some performed by using ultrasonography (USG)) and the difficult laryngoscopic view in neonates and infants.

Design: This is a prospective, single blinded, observational study. The number of patients was calculated as follows: A sample of 12 from the positive group (difficult laryngoscopy group) and 96 from the negative group (easy laryngoscopy group) achieve 80% power to detect a difference of 0.25 between the area under the ROC curve (AUC) under the null hypothesis of 0.50 and an AUC under the alternative hypothesis of 0,75 using a two-sided z-test at a significance level of 0.05.

Methods: All patients which is newborn and infant age group undergoing elective surgery requiring intubation under general anesthesia are assessed. Patients' age, body mass index (BMI), thyromental distance, mandibula length, the distance between the lip corner and ipsilateral ear tragus, and the transverse length (measured by hand sign-middle-ring fingers adjacent side by side) measurements are recorded. In thyromental distance measurement, "thyroid notch" are determined by USG.

The laryngoscopic view is graded by a different experienced anaesthetist who is blinded to the airway measurements.

Statistical analysis:

Receiver operating characteristic (ROC) curves are used to determine the best cut-off point for distance variables in the separation of difficult and easy laryngoscopy groups. Sensitivity, selectivity, positive predictive value and negative predictive values of lengths are calculated according to determined cut point.The difference between the two groups in terms of qualitative variables are evaluated by chi-square or Fisher's exact test. The normal distribution of the numerical variables are examined with the Shapiro-Wilk test. The difference between the two groups in terms of numerical variables are investigated by Mann Whitney U test. Values of p <0.05 are considered as statistically significant.

Inclusion Criteria:

• Newborn and infant age group
• Undergoing elective surgery requiring intubation under general anesthesia

Exclusion Criteria:

• History of congenital maxillofacial defect,
• History of upper airway pathology (tumor, cleft palate-lips, etc.)
• History of head and neck trauma (fracture, swelling, scar )

Newborn and infant age group undergoing elective surgery at Ankara Childrens' Health and Diseases Hematology Oncology Training and Research Hospital