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