Vagally Mediated Heart Rate Variability and Mood States in Patients with Chronic Pain Receiving Prolonged Expiration Regulated Breathing: A Randomized Controlled Trial.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 39180643 · doi:10.1007/s10484-024-09660-3
What was done
Fifty patients with chronic pain (aged 20–67 years) were randomized 1:1 into an intervention group or a control group. The intervention group performed metronome-cued breathing targeting an inspiration-to-expiration (I:E) ratio of 28:72 (0.38) at 12 breaths per minute, achieving a measured mean I:E ratio of 0.685 (SD 0.48). The control group observed the metronome without conscious breathing modification, showing a mean I:E ratio of 0.745 (SD 0.69). Investigators measured vagally mediated heart rate variability (HF-HRV and RMSSD), respiration via strain gauge, and self-reported mood using the Brief Mood Introspection Scale (BMIS).
What was found
Low I:E breathing produced a statistically significant increase in HF-HRV and RMSSD (repeated measures ANCOVA, Bonferroni-adjusted post-hoc p < 0.05). In mood ratings, low I:E breathing led to an increase in positive-mood states and a decrease in aroused mood states (repeated measures ANOVA, p < 0.05). In contrast, the control condition resulted in an increase in aroused mood state (p < 0.05). Exact numerical values and effect sizes for HRV and BMIS scores were not provided in the abstract.
Why it matters
This indicates that a simple, paced breathing exercise with prolonged exhalation can acutely augment parasympathetic tone and reduce arousal in patients with chronic pain.
Limits
The study evaluated only immediate post-intervention effects, without assessing clinical pain severity or long-term retention. The sample size was modest (n = 50), the intervention group fell short of the targeted 0.38 I:E ratio (achieving 0.685), and specific underlying pain etiologies were not detailed in the abstract.