The Effect of Deep Breathing and Transcutaneus Electrical Nerve Stimulation on Heart Rate Variability

This interventional study aims to investigate the effect of deep breathing (DB) and transcutaneous electrical vagus nerve stimulation (tVNS) on heart rate variability (HRV) in healthy participants and patients with rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE). HRV is used as a surrogate measure of vagal nerve tone. The study consists of three sub-projects: Sub-project 1: To compare the effect of one session of DB and one session of non-invasive auricular tVNS on vagal nerve tone measured by HRV in healthy participants and in patients with RA and SLE. The hypotheses is that DB has a similar effect on HRV as non-invasive electrical tVNS. Sub-project 2: A dose-response study in healthy participants comparing the effect of 5, 15 and 30 minutes of DB on HRV. The hypothesis was that HRV increases as a function of the number of minutes the DB is performed in healthy participants. Sub-project 3: To investigate the effect of the optimal dose found in sub-project 2 in patients with RA and SLE measured by HRV, and to investigate its reproducibility by doing it twice.The hypothesis was that HRV increases after DB in patients with RA and SLE, and the effect is reproducible. In all three sub-projects the washout period will be investigated by measuring HRV three times after the intervention. We hypothesise that the effect of DB and tVNS on HRV decreases over time.