Effect of Breathing Training on Symptoms of Gastroesophageal Reflux Disease

Participants in the experimental group will perform volume-oriented incentive spirometry training twice daily (morning and evening) for 6 weeks. Each session consists of 10 deep inspirations using the spirometer, with the target volume initially set according to the participant's predicted maximum inspiratory capacity and increased by approximately 5% each week starting from week 2. For each breath, participants inhale to reach the target volume, hold their breath for 3-5 seconds, and then exhale. A rest period of 30-60 seconds is allowed between maneuvers, and the pace is adjusted according to individual tolerance. Training is performed in a seated or semi-recumbent position.

Participants in the control group will perform diaphragmatic breathing exercises twice daily (morning and evening) for 6 weeks. During weeks 1-2, each session consists of 10 breaths per set; from week 3 to week 6, each session consists of 15 breaths per set. The exercise is performed without devices and includes the following sequence: slow inspiration through the nose with abdominal expansion, holding the breath for 5 seconds, followed by exhalation through the mouth with visible abdominal contraction. After each set, participants rest with natural breathing for 1-2 minutes to prevent hyperventilation or diaphragmatic fatigue. Training is conducted in a semi-recumbent position with both hands placed behind the head, focusing on abdominal movement control and breathing rhythm.

Participants in the control group will receive usual clinical care for gastroesophageal reflux disease (GERD) without structured breathing training. At study entry, participants are provided with standardized patient education regarding GERD and lifestyle modification strategies, along with an educational leaflet. No specific posture or breathing exercises are required during the study period.