Predictors of failed intubation in patients with obesity-A systematic review

Difficult airway management is a serious issue in anesthetic practice, especially for patients with obesity, whose anatomical and physiological alterations make intubation difficult. Multiple predictors have been investigated, yet no clear consensus exists. This systematic review aimed to comprehensively identify reliable predictors of failed, or difficult intubation in adult patients with obesity.

PRISMA 2020 guidelines were used in this study. Systematic searches were performed using the search engines of the databases PubMed, PubMed Central, Google Scholar, CrossRef, and CORE from 2015 to 2025. This study considered studies evaluating clinical or anatomical, or ultrasound-based predictors for difficult or failed intubation in adult patients with obesity.

Thirty-five trials were suitable for inclusion. The most important predictive factors were found to be neck circumference (NC) and particularly the neck-circumference-to-thyromental-distance ratio (NC/TMD) of ≥5.0. Ultrasound-derived parameters demonstrated superior diagnostic accuracy compared to traditional bedside assessments. Regarding quality of the included studies, 26 (74.3%) studies had low risk of bias, and eight studies (22.9%) had moderate risk, suggesting a high level of quality.

The NC/TMD ratio, neck circumference, and thyromental distance are the most reliable predictors of difficult or failed tracheal intubation in patients with obesity. Body mass index alone lacks predictive accuracy, while incorporating ultrasound measurements enhances diagnostic precision.