A Heart Rate Variability (HRV) Biofeedback Training in Functional Gastrointestinal Disorders (FGID)

The intervention involves 5 training sessions lasting 45 minutes (specifically, 5-minute baseline and 5 HRV biofeedback trials lasting 5 minutes each) according to the protocol published by Lehrer et al. (2013). Physiological signals (ECG and respiratory rate) will be recorded during all sessions. During the training, participants will see on the screen a graph representing heart rate superimposed on a graph representing abdominal breathing. They will be asked to synchronize the two signals so that the changes in heart rate are in phase with the respiratory cycle in order to maximize the difference between the maximum and minimum heart rate within each respiratory cycle \[i.e., respiratory sinus arrhythmia (RSA), an index of vagal modulation on the heart\] (Lehrer et al., 2003; Lehrer et al., 2000).

The Placebo procedure requires participants to attend 5 sessions lasting 45 minutes during which they perform a task. Physiological signals (ECG and respiration rate) will be recorded during all sessions. Participants will see on the screen a graph representing heart rate superimposed on a graph representing abdominal breathing but these will not directly reflect the subject's cardiorespiratory activity. Participants in the control group will be asked to synchronize the two signals so that the changes in heart rate are in phase with the respiratory cycle, but the feedback on the screen will not reflect that subject's RSA changes.