Assessment of three methods of pH probe positioning in preterm infants

Abstract

Background: In the assessment of gastroesophageal reflux, correct placement of the pH catheter is crucial. This is particularly so in very low birth weight infants where a small error in positioning could give rise to a potentially large error in results. Accepted modes of assessing correct positioning can be problematic in this population of infants and alternative methods were investigated.

Methods: A total of 26 preterm infants (<35 weeks gestation) were enrolled in this study. All infants were suspected of having GOR and pH monitoring was performed. Probe position was assessed using Strobel's formula, manometry and acid-alkali interface and confirmed by chest x-ray.

Results: There was a highly significant positive correlation between the calculation of the pH probe position using Strobel's formula and the position on x-ray and a significant positive correlation between the acid/alkali interface and x-ray position. There was no correlation between manometry and x-ray position and this method was also shown to be problematic in its' application.

Conclusion: The data suggests that it is appropriate to use Strobel's formula as a method of accurate positioning of pH probes in preterm infants, thus avoiding the need for additional x-rays. The acid/alkali interface, when obtainable, is a secondary, satisfactory method to confirm the position calculated by Strobel's formula.