What is the best method for calculating the optimal position of an esophageal pH probe in children?

How Best to Estimate Insertion Length of Multichannel Intraluminal Impedance pH Probes in Children

OBJECTIVE

To assess the reliability of the KidZ Health Castle formula (KHC-F) to determine the correct probe position of a multichannel intraluminal impedance pH.

STUDY DESIGN

A retrospective cohort study was performed on 222 children between 1 month and 18 years of age undergoing multichannel intraluminal impedance pH. The primary outcome was the comparison of the pH sensor location determined by the KHC-F with the radiological target position. The margin of error was defined as 1 cm from the target position. Performance of the KHC-F and existing formulas was determined via the percentage with a correct position, mean error, 95% limits of agreement (Bland-Altman plots), and Spearman correlation. A post hoc analysis was performed with an updated KHC-F v2, subtracting -0.5 cm from the KHC-F.

RESULTS

Positioning with KHC-F was correct in two-thirds of the participants, with a very strong correlation (ρ = 0.91) with the target position. Bland-Altman plots showed good agreement between KHC-F and target position (mean error of -0.44 cm, lower limit -3.2 cm, upper limit 2.3 cm). A post hoc analysis with the KHC-F v2 showed a correct positioning in 74% of patients. Comparison with other formulas showed a stronger performance of KHC-F and KHC-F v2 on correct positioning, mean error, and 95% limits of agreement.

CONCLUSIONS

The KHC-F leads to reliable results. KHC-F v2 outperforms all other existing formulas in children, thereby reducing the need for repositioning and the amount of x-ray exposure. The age distribution of the sample may be a limitation, as well as the retrospective nature of the study.

Esophageal length in children: Reference data and a novel predictive equation

Minimal information exists on the length of the child's esophagus, namely the distance from the cricopharyngeus to the esophagogastric junction (EGJ). We aimed to investigate the relationship between esophageal length (EL) and the age, height, and weight of the child. Children undergoing upper gastrointestinal endoscopy between February 2019 and May 2021 at our institution were prospectively audited. Children with anatomical esophageal disorders were excluded. Endoscopic distances from the incisors to the cricopharyngeus and EGJ were obtained, and novel predictive equations derived to predict EL. Intra-observer agreement for endoscopic measurements showed an intra-class correlation coefficient of 0.99. A total of 290 children aged 0.4-17.3 years were included in the analysis; they were divided into a model development cohort (n = 261) and a model validation cohort (n = 29). Measured EL correlated best with height (r = 0.92) as compared to age (r = 0.90) or weight (r = 0.83). The optimal equation for predicting EL was 0.156 × height (cm) - 1.336 (adjusted R²  = 0.841); this had a success rate of 76% in the validation cohort. The optimal equation for predicting distance from incisors to EGJ was 0.199 × height (cm) + 6.470 (adjusted R²  = 0.889); this had a success rate of 69% in the validation cohort. This is the first study to report a predictive equation for estimating esophageal length in children. Accurate prediction of esophageal length may assist with clinical esophageal procedures in children such as nasogastric and pH probe placement.