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Assessment of three methods of pH probe positioning in preterm infants
Anthony J B Emmerson1, Terri Chant, Judith May
1Neonatal Medical Unit, St. Mary's Hospital, Whitworth Park, Manchester, UK. anthony.mmerson@man.ac.uk
Insights
Accurate pH probe placement in preterm infants is vital for gastroesophageal reflux assessment. Strobel's formula offers a reliable, non-radiographic method for precise pH catheter positioning in this vulnerable population.
Area of Science:
- Neonatal Medicine
- Pediatric Gastroenterology
- Medical Device Technology
Background:
- Accurate gastroesophageal reflux (GER) assessment in neonates relies on precise pH catheter placement.
- Very low birth weight infants present unique challenges for pH monitoring due to potential for significant measurement errors from minor positioning inaccuracies.
- Established methods for verifying catheter placement in infants are often problematic, necessitating investigation into alternative techniques.
Purpose of the Study:
- To evaluate the accuracy of Strobel's formula, manometry, and the acid-alkali interface for pH probe positioning in preterm infants.
- To identify a reliable, non-invasive method for confirming pH catheter placement, potentially reducing the need for radiographic confirmation.
Main Methods:
- Twenty-six preterm infants (<35 weeks gestation) with suspected GER underwent pH monitoring.
- Probe position was initially assessed using Strobel's formula, manometry, and the acid-alkali interface.
- Final confirmation of probe placement was achieved through chest x-ray.
Main Results:
- A strong positive correlation was observed between pH probe position calculated by Strobel's formula and x-ray confirmation (p<0.001).
- A significant positive correlation was found between the acid-alkali interface method and x-ray positioning.
- Manometry showed no correlation with x-ray position and proved difficult to apply in this infant cohort.
Conclusions:
- Strobel's formula is a suitable and accurate method for positioning pH probes in preterm infants, potentially eliminating the need for routine chest x-rays.
- The acid-alkali interface serves as a reliable secondary method for confirming pH probe position when calculable, complementing Strobel's formula.
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.