pH probe study helps determine if a baby or child has reflux.  One passes
a little tube in the nose 2/3 of the way down the esophagus.  At the end
of the little tube is a sensor which detects the pH (acidity) of the
esophagus every so many seconds.  It transmits the info to a computer
chip and you can buid a graph of the changes in pH over 24 hours.  It is
particularly helpful for babies with apnea if you want to know if such an
event is related to reflux.

To obtain a pH probe study it is not necessary to take baby off the
breast.  Just record feeding times.  Some use apple juice feeds every
other feed because they feel that some babies may not have enough stomach
acid to interpret the probe. so they feel apple juice (beeing acid) would
compensate for the lack of acid in the baby's stomach.

Let me know if any further questions about this issue

Maryelle