Esophageal pH Monitoring in Children: A Simple Mathematical Formula for pH Probe Positioning

Simple Formula for pH/Impedance Probe Positioning in Children-Time to Update Standard Practice?

OBJECTIVE

To develop a novel formula for pH probe placement with adequate accuracy.

METHODS

Children (3-18 y) undergoing pH-metry were prospectively evaluated. Their height and corrected pH probe position under X-ray (2 vertebrae above the diaphragm) was recorded and the linear-regression analysis was performed to derive a novel formula. Its accuracy was checked on an additional group of prospectively included children. The success rate of a newly developed formula was estimated and compared to the performance of previously used formulae. The difference in the suggested placement of the probe (cm from nostrils) was calculated.

RESULTS

Based on 670 children with pH probe placed under X-ray, the following formula was developed using the linear-regression analysis: L = 0.184x + 4.4 (cm) (L = probe placement depth, x = body height). Its accuracy was confirmed on additional 111 children resulting in almost 85% success rate. The formula showed significant difference in the suggested placement from formulae used previously: +4.9 ± 0.8 cm, +2.4 ± 0.1 cm, +0.7 ± 0.6 cm, +1.1 ± 0.4 cm, +1.8 ± 0.3 cm, +2.2 ± 0.5 cm from the one by the Strobel, Moreau, Wilson, Nowak, Staiano-Clouse formulae, and the GOSH table with the calculated success rates of 1.8%, 43.2%, 65.8%, 77.5%, 65.8% and 54.1%, respectively. A table suggesting placement depth based on the body height was developed.

CONCLUSION

The present formula provides 85% success of pH probe placement in children ≥ 3 y suggesting its use in routine practice. More data are needed to confirm that probe adjustment under X-ray is unnecessary.

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.

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

In assessment of distal esophageal pH, the sensor of the probe should be placed above the upper border of the lower esophageal sphincter. There are several methods to estimate the distance from the nose where the probe should be fixed according to the patient's height. We studied the accuracy of these methods. Data of patients who underwent esophageal monitoring were collected prospectively. The esophageal pH electrode was set with the aid of fluoroscopy in all cases, considering the location recommended by the current guideline. Esophageal probe position and anthropometric data of each patient were recorded. We compared the actual esophageal pH electrode distance from the nose with that estimated by Nowak's, Strobel's, Staiano-Clouse's, and Moreau's formulae and the Great Ormond Street Hospital (GOSH) table. A total of 98 patients were included, with ages ranging from 2 months to 19 years old. The highest success rate (67%) for all age groups was achieved by Nowak's formula (3.2 + 0.2 × height in cm). Considering only children under 3 years old, the GOSH table reached the highest-yet probably overestimated-fraction of adequate predictions. A corrected Staiano and Clouse's formula (4.28 + 0.191 × height in cm) had a slightly lower success rate than Nowak's due to a poorer performance in younger children. In conclusion, Nowak's formula is the most accurate regardless of age. It can help reduce radiation due to systematic fluoroscopy, as well as the subsequent manipulation of the esophageal probe. However, it still leads to pH sensor misplacements in more than one-third of children. In consequence, a confirmatory X-ray is advisable even after using the formula.

Gastroesophageal reflux is not associated with short-term variability of parasympathetic activity in children

PURPOSE

A lower parasympathetic activity was described in patients with the gastroesophageal reflux disease. We aimed to determine whether gastroesophageal reflux (GER) episodes are associated with a short-term parasympathetic tone variability in children.

METHODS

In order to address this question we performed simultaneous 24-h esophageal multichannel intraluminal impedance-pH and electrocardiographic monitoring in 16 children (age range 6-18 years), including 8 with asthma and 2 with gastroesophageal reflux disease. After describing duration, height, and acidity of 483 GER episodes we also measured parasympathetic-related heart rate variability parameters in 4 time periods: preceding, containing, following GER, and in-between GERs (control). High frequency (HF) power and root-mean square differences of successive R-R intervals (r-MSSD) were assessed in 2.5-min and 1-min periods, respectively.

RESULTS

We did not identify the searched short-term parasympathetic tone changes.

CONCLUSIONS

In conclusion, GER episodes and their characteristics were not associated with short-term variability of parasympathetic activity in children.