Presently, the exact mechanism of GERD and the role of CO2 in pathogenesis of heartburn symptoms is unclear. CO2 conversion to protons may play a key role in the mechanism for heartburn sensation. This is a prospective, randomized study that will help further explore the mechanism for heartburn sensation in GERD patients and can be a prelude for further studies examining the role of new class antireflux agents such as carbonic anhydrase inhibitors in the treatment of patients with heartburn.