48 Hours Esophagal pH-monitoring With and Without Gaviscon

At a esophagal pH-monitoring will the classic 24-hour measurement be extended to 48 hours. During the first 24 hours are the measurements without medication. After 24 hours the treatment will be started with Gaviscon and will the next 24 hours the measurements under the medication happen. Normally is the medication required after the measurements. With this study the investigators will have multiple measurement points to compare.