Can chin-nape circumference and the ratio of neck circumference to chin-nape circumference predict difficult mask ventilation or difficult intubation in obese patients?

We aimed to evaluate the success of the ratio of chin-nape circumference (CNC) and neck circumference (NC) to CNC in predicting difficult mask ventilation (DMV) or difficult intubation (DI). Eighty-seven obese patients (body mass index ≥ 30) were evaluated between September 15, 2019 and September 15, 2020. Mallampati score, mouth opening, upper lip bite test, distance between incisors, thyromental distance (TMD), sternomental distance (SMD), and thyromental height were recorded. NC and CNC were measured in a neutral position. The ratio of NC to TMD and the ratio of NC to CNC were calculated. Mask ventilation was graded according to the method described by Han et al (Grade 3 or 4 equals DMV). DI assessment was performed using the intubation difficulty scale (IDS, IDS < 5 equals easy intubation, IDS ≥ 5 equals DI). Logistic regression analysis was performed to identify the variables thought to be effective in DMV and DI. Receiver operating characteristic curves were generated for each parameter considered effective. DMV was found in 17.2% (n = 15) of the patients included in the study, and DI was found in 16.1% (n = 14). The relationship between DMV and age, male gender, obstructive sleep apnea syndrome, NC, ratio of NC to TMD, ratio of NC to SMD, ratio of NC to CNC, and CNC was significant. Male gender and NC >45.5 cm were independent risk factors for DMV. The relationship between DI and distance between incisors, NC, ratio of NC to TMD, ratio of NC to SMD, and CNC was significant. A distance between the incisors < 4.85 cm and a NC > 41.5 cm were found to be independent risk factors for DI. CNC may predict DMV and DI in obese patients. The ratio of NC to CNC may predict DMV in obese patients.