Properties of Thermal Analgesia in a Human Chronic Low Back Pain Model
Received 7 May 2020
Accepted for publication 10 July 2020
Published 13 August 2020 Volume 2020:13 Pages 2083—2092
Checked for plagiarism Yes
Review by Single anonymous peer review
Peer reviewer comments 3
Editor who approved publication: Dr Robert B. Raffa
Charles Chabal,1 Peter J Dunbar,1 Ian Painter,2 Douglas Young,3 Darah C Chabal4
1Soovu Labs Inc., Seattle, WA, USA; 2Department of Health Services, University of Washington, Seattle, WA, USA; 3Northern California Research, Sacramento, CA, USA; 4Biology Department, University of Washington, Seattle, WA, USA
Correspondence: Charles Chabal
Soovu Labs Inc., Seattle, WA, USA
Tel +1 206-579-4910
Purpose: For years, heat has been used for comfort and analgesia is recommended as a first-line therapy in many clinical guidelines. Yet, there are questions that remain about the actual effectiveness of heat for a condition as common as chronic low back pain, and factors such as time of onset, optimal temperature, and duration of effect.
Materials and Methods: A randomized double-blinded controlled trial was designed to compare the analgesic response to heat delivered via pulses at 45°C (experimental group, N=49) to steady heat at 37°C (control group, N=51) in subjects with longstanding low back pain. Treatment lasted 30 minutes with follow-up out to four hours. The hypothesis was that the experimental group would experience a higher degree of analgesia compared to the control group. Time of onset and duration of effect were also measured.
Results: Both groups were similar in average duration of pain (10.3 years). The primary outcome measure was pain reduction at 30 minutes after the end of treatment, using a 10-points numeric pain scale. Reduction in pain was greater for the experimental group than the control group (difference in mean reduction = 0.72, 95% CI 0.15– 1.29, p = 0.014). Statistically significant differences in pain levels were observed from the first measure at 5 minutes of treatment through 120 minutes after completion of treatment. Reduction in pain associated movement was greater in the active heat group than the placebo group (p = 0.04).
Conclusion: High-level pulsed heat (45°C) produced significantly more analgesia as compared to steady heat at 37°C at the primary end point and for an additional 2 hours after treatment. The onset of analgesia was rapid, < 5 minutes of treatment. The results of this trial provide insight into the mechanisms and properties of thermal analgesia that are not well understood in a chronic low back pain model.
Keywords: thermal analgesia, heat, chronic low back pain
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