Correlation Between External Body Parameters and Nares-to-Vocal Cord Distance

Introduction Nares-to-vocal cord distance (NVD) is an important anatomical parameter for safe nasotracheal intubation and optimal positioning of nasopharyngeal devices. This study evaluated the relationship between NVD and easily obtained external body measurements in adult surgical patients. Materials and methods We conducted a prospective observational study in adults of both sexes undergoing elective surgery under general anesthesia. Using a fiberoptic bronchoscope, we measured NVD from the external nares to the level of the vocal cords. External measurements included height (Ht), weight (Wt), nares-ear tragus distance, nares-mandible angle distance, nares-thyroid distance, thyromental distance, sternomental distance (SMD), sternal length, arm span, and the distance from the external occipital protuberance to the tip of the C7 spinous process (OC7). We assessed correlations between NVD and these anthropometric parameters. Results All external body measurements and NVD were greater in men than in women. In the overall cohort and in men, NVD showed the strongest positive correlation with OC7, followed by SMD, Ht, and Wt. In women, NVD also correlated significantly with OC7, Wt, and SMD, although the strength and consistency of these associations were lower than in men. Age and several other external measurements showed little or no meaningful correlation with NVD. Conclusions NVD demonstrates clinically relevant associations with simple bedside anthropometric measures, particularly OC7, SMD, Ht, and Wt. These findings suggest that readily obtained external measurements may help clinicians estimate NVD when planning nasotracheal intubation or positioning nasopharyngeal devices, especially in settings where fiberoptic assessment is unavailable. Further research across broader, more diverse populations is needed to refine these relationships and support the development of practical prediction tools for airway management.