How to Position pH-Impedance Probes in Pediatric Patients

Abstract

Background: Multichannel intraluminal-impedance (MII)—pH recording is used frequently for the diagnosis of gastroesophageal reflux disease in children. The location of the pH-sensor is essential to obtain a reliable recording. Positioning of the electrode through radiologic control is recommended as standard. In order to decrease radiation, different attempts have been made to develop equations to obtain a correct positioning of the probe without radiation.

Methods: We prospectively compared the location of the pH-sensor in 212 children according to a formula developed by our nurses (“distance (nose tip to ear canal) + (nose tip with head in neutral position to nipple line) in cm”) to the location determined by fluoroscopy at the seventh posterior rib, which is considered the gold standard. The probe was considered malpositioned if the distance of the formula differed more than 1 cm compared to fluoroscopic control. Statistical analyses were done using R version 4.0.3. Spearman correlation coefficients, mean error and 95% limits of agreement of Bland–Altman plots were calculated. A p-value of <0.05 was considered statistically significant.

Results: According to the overall results, the spearman correlation between the formula and fluoroscopic control was excellent (ρ = 0.91). In 67% of the patients, the location according to the formula was correct, if a difference of 1 cm above or below the exact location is accepted.

Conclusions: The formula adequately predicts the location of the MII-pH probe in 67% of the children (exact distance ±1 cm). In 9% of the children the difference was over 2 cm. Each center should decide: accept about 10% of dislocations of the pH-sensor of 2 cm or more or continue with the radiologic control.