title: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Neonatal Medical Unit, St. Mary's Hospital, Whitworth Park, Manchester, UK. anthony.mmerson@man.ac.uk
authors.forename: Anthony J B
authors.initials: AJ
authors.lastname: Emmerson
authors.forename: Terri
authors.initials: T
authors.lastname: Chant
authors.forename: Judith
authors.initials: J
authors.lastname: May
authors.forename: Patricia
authors.initials: P
authors.lastname: Vales
mesh_terms: D001827:Body Height; D004947:Esophagus / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D005764:Gastroesophageal Reflux / Q000175:diagnosis*; D005865:Gestational Age; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D008365:Manometry; D008433:Mathematics; D011859:Radiography