Predicting Nasopharyngeal Depth in Children Using Body Measurements: A Pilot Study

ImportanceA predictive formula for pediatric nasopharyngeal depth (ND) could tailor nasopharyngeal swabbing technique to individual anatomy and reduce the incidence of false negatives.ObjectiveTo provide a formula predicting ND based on surface anatomy measurements in children.Study DesignProspective pilot study.SettingBritish Columbia Children's Hospital Pediatric Otolaryngology Clinic (Canada) between June 2022 to May 2024.ParticipantsChildren receiving flexible nasal endoscopy at a tertiary otolaryngology clinic.Intervention and Main Outcome MeasuresPredictor variables collected were sex, age, height, weight, curved nasal ala-tragus distance, finger lengths, and history of adenoidectomy. The outcome variable of ND was measured from the nasal nares to the posterior nasopharyngeal wall during routine nasal endoscopy. Relationships between predictor and outcome variables were analyzed. A predictive formula for ND was generated using stepwise linear regression, formula simplification, and model validation.ResultsSixty-three pediatric patients were included (67% male, average age 6.4 years, range 3 weeks-18 years). ND differed by age: average ND for age <2 was 5.4 ± 0.8 cm, ages 2 to 10 was 7.4 ± 1.1 cm, and ages >10 was 9 ± 1.1 cm. Stepwise linear regression resulted in the formula: ND (cm) = ⅔ (pinky length) + ⅓ (ala-tragus distance) + 1 (if history of adenoidectomy) + 1. R² was .78 with an average error of estimation ±0.81 cm.ConclusionPediatric ND varies with age and surface anatomy dimensions. ND can be predicted in children using simple bedside measurements of pinky length, curved ala-tragus distance, and history of adenoidectomy using the equation ND (cm) = ⅔ (pinky length) + ⅓ (ala-tragus distance) + 1 (if history of adenoidectomy) + 1.RelevanceFuture studies are required to further validate the proposed predictive formula to ultimately improve accuracy in procedures involving blind instrumentation of the nasal cavity, such as nasopharyngeal swabs and posterior nasal packing.