Volume-Oriented Incentive Spirometry-Assisted Diaphragmatic Breathing Exercise for Functional Heartburn or Reflux Hypersensitivity

The goal of this pilot randomized controlled trial is to determine whether volume-oriented incentive spirometry-assisted diaphragmatic breathing exercise (VIS-assisted DBE) can improve reflux-related symptoms and health-related quality of life in adults with functional heartburn (FH) or reflux hypersensitivity (RH). The main questions it aims to answer are: Does VIS-assisted DBE reduce reflux-related symptoms compared with usual care? Does VIS-assisted DBE improve health-related quality of life compared with usual care? Researchers will compare VIS-assisted DBE plus usual care with usual care alone to determine whether the intervention provides additional benefits in symptom relief and quality of life. Participants will: Complete baseline clinical evaluations and symptom questionnaires. Be randomly assigned to either the VIS-assisted DBE group or the usual care group. Receive either VIS-assisted diaphragmatic breathing exercises twice daily for 20 minutes over a 4-week period in addition to usual care, or usual care alone. Complete follow-up assessments after the 4-week intervention, including symptom and quality-of-life questionnaires