Respiratory hypoalgesia? The effect of slow deep breathing on electrocutaneous, thermal, and mechanical pain

The aim of the study reported in this paper is to investigate the effect of slow-deep breathing (SDB) on self-reported pain, heart rate variability, and baroreflex sensitivity (BRS). These effects are examined in 3 separate experiments, each using a different phasic pain modality. For each experiment, different subjects were recruited. Eighty-three healthy female participants were instructed to breathe guided by a visual cue at a slow frequency (SDB: .1 Hz), and at a frequency close to the spontaneous breathing frequency (normal paced breathing, .2 Hz). Pain was induced during instructed breathing using electrocutaneous (experiment 1, n .31), thermal (experiment 2, n . 28), or mechanical stimuli (experiment 3, n = 24). Participants were requested to rate the intensity of each painful stimulus (Numerical Rating Scale) and subjective level of pleasantness, arousal, and dominance (self-assessment manikin). During the experiment, R-R interval, blood pressure, tidal volume, and end-tidal CO2 were continuously measured. Results for self-reported pain, self-assessment manikin, and physiological measurements were consistent across the 3 experiments. Although SDB significantly increased baroreflex sensitivity and heart rate variability, self-reported pain did not differ between breathing conditions, regardless of pain modality. Other potential mechanisms or components should be considered such as behavioral modulators including relaxation and treatment expectation.

Perspective: Merely slowing down the breathing frequency to .1 Hz is not sufficient to induce hypoalgesia, despite the significant physiological effects associated with SDB compared to spontaneous breathing. (C) 2020 U.S. Association for the Study of Pain. Published by Elsevier Inc. All rights reserved.