Baseline esophageal impedance according to different time intervals.

Baseline impedance (BImp) reflects esophageal integrity. The study aims to identify the optimal method to calculate BImp. Mean BImp was calculated in 20 consecutive multichannel intraluminal impedance recordings including and excluding impedance events (IEs) (reflux, swallows, and gas episodes) in all channels during the full recording and during the first period of 1 minute without an IE every hour (method 1), every 2 hours (method 2), or 4 hours (method 3). BImp obtained during the total recording was set at 100%, and the variation (difference in BImp for the different methods) and variability (difference in BImp during one analysis period) were assessed. All children underwent endoscopy. No child had esophagitis. The mean difference over the six channels, in percentage, between BImp over the total recording with and without IE was ≈ 1.2% and comparable for each channel (range -5.87-6.99%). A mean of 980 IE were excluded in each tracing, and it took between 4 and 24 hours to delete all events in one tracing. The difference of BImp obtained with and without IE was mainly caused by the gas episodes at the upper and swallows in the lower channel. The mean BImp according to the three 1-minute analysis methods was comparable with the mean BImp according to the 24-hour analysis. The automatic determination of the mean BImp over the total tracing including the IE is an adequate method. In isolated tracings with numerous IE, the calculation of the mean BImp over 1 minute every 4 hours is an alternative option. Companies should develop software to calculate the mean BImp during the whole registration deleting all IE for the analysis.