HEART rate variability biofeedback breathing programme for LOng Covid dysautonomia (HEARTLOC): results of a feasibility study

Introduction Post-covid-19 syndrome, or Long covid (LC) refers to symptoms persisting 12 weeks after Covid-19 infection. LC comprises a wide range of dysautonomia symptoms, including fatigue, breathlessness, palpitations, dizziness, pain and brain fog. This study tested the feasibility and estimated the efficacy, of a Heart Rate Variability Biofeedback (HRV-B) technique via a standardised slow diaphragmatic breathing programme in individuals with LC. Methods and Analysis LC patients underwent a 4-week HRV-B intervention for 10 minutes twice daily for a total of 4 weeks using the Polar H10 ECG (Electrocardiogram) chest strap and Elite HRV phone application. Outcome measures C19-YRSm (Yorkshire Rehabilitation Scale modified), EQ5D-5L (EuroQol 5 Dimensions), Composite Autonomic Symptom Score (COMPASS-31), WHO Disability Assessment Schedule (WHODAS), and Root Mean Square of Successive Differences between heartbeats (RMSSD) using a Fitbit device were completed before and after the intervention. The study was pre-registered at clinicaltrials.gov NCT05228665 . Results 13 participants (54% female, 46% male) completed the study with high levels of data completeness and adherence. There was a statistically significant improvement in C19YRS-m (p=0.001), EQ5D Global Health Score (p=0.009), COMPASS-31 (p=0.007), RMSSD (p=0.047) and EHODAS (p=0.02). Qualitative feedback suggested participants were able to use it independently, were satisfied with the intervention, and reported beneficial effects from the intervention. Conclusion This is the first study in the literature to report that HRV-B is a feasible intervention for LC and seems to be potentially improving symptoms of LC and dysautonomia. Article summary Strengths and limitations of the study To our knowledge, this is the first study of HRV-B in long covid and dysautonomia and has shown the feasibility of a novel technology-based intervention in a home setting. There was a statistically significant improvement in LC symptoms, functional ability, quality of life and dysautonomia scores. The study provides an estimation of efficacy which will determine the sample size for a larger controlled trial in LC and dysautonomia. The main limitation of this study is the small sample size and uncontrolled design which might not give us an accurate estimate of efficacy. The sample was predominantly Caucasian participants, 54% of whom were female. The take-up for HRV-B in those with a lack of experience in using digital technology and those from less privileged backgrounds is unknown.