Breathing Interventions Improve Autonomic Function, Respiratory Efficiency and Stress in Dysfunctional Breathing: A Randomised Controlled Trial

Background: Dysfunctional breathing patterns may impair autonomic regulation and increase perceived stress. Breathing-based interventions, particularly those involving guided exercises and supportive tools, have the potential to provide non-pharmacological benefits. Methods: In this parallel two-arm randomized controlled trial, 14 women aged 35–45 years with signs of dysfunctional breathing and no comorbidities were recruited from a fitness club. Participants were randomly assigned (1:1) using a computer-generated sequence to an intervention group (n = 7) or a control group (n = 7). Blinding was not applied. Both groups completed a 6-week program of guided breathing exercises using the iBreathe app, while the intervention group additionally used mouth tape during sleep. The primary outcomes were heart rate variability (HRV) indices—root mean square of successive differences (RMSSD) and the high-frequency (HF) component. Secondary outcomes included respiratory rate, Hencho test performance, and perceived stress measured using the Perceived Stress Scale-10 (PSS-10) and a Visual Analogue Scale (VAS). All participants were included in the final analysis (no loss to follow-up). Results: The intervention group showed a significant increase in the HF component of HRV (p = 0.018) and improved Hencho test performance (p = 0.018). Both groups demonstrated significant reductions in respiratory rate (p < 0.05) and PSS scores (p < 0.05). Between-group differences were not significant for RMSSD or perceived stress. No adverse events were reported. Conclusions: A 6-week breathing intervention improved respiratory efficiency and reduced perceived stress among women with dysfunctional breathing. The additional of night-time mouth taping provided further benefits for HRV and respiratory control. Larger and longer trials are needed to confirm these findings.