Impedance has helped physicians gain a better understanding of the role non-acidic things refluxing from the stomach into the esophagus, and even beyond, into the lungs. Until recently physicians had only the pH test to detect reflux, thus were measuring only acid. With strong medicine to decrease acid secretion (PPIs), it is important to understand why patients with GERD still have symptoms, despite taking these medications. Impedance measures electrical resistance between two electrodes. When multiple pairs of electrodes are placed within the esophagus with a catheter, physicians can detect acid and non-acid reflux. This technology was first introduced to the Pacific Northwest several years ago at the University of Washington Medical Center, and we have been on the forefront of research to determine the utility of impedance in the workup of GERD.