• Sung Tae Koo, Yong Il Shin, Da Young Lee, and Chang-Hyung Lee.
• Division of Meridian and Structural Medicine, Pusan National University School of Korean Medicine; Rehabilitation Medicine, Pusan National University School of Medicine, Research Institute for Convergence of Biomedical Science and Technology.
• Pain Physician. 2015 Jan 1;18(1):E39-45.

BackgroundWe previously published on the pressure effect using a rheumatoid animal model (Pain Physician in 2013 and 2014). However, we do not know how long the pressure effect lasts after exposure to high pressure.ObjectiveWe evaluated the duration of the pressure effect in a day for a given study period.Study DesignLaboratory animal study.MethodsFollowing injection of Complete Freund's Adjuvant (CFA) into one side of the knee joint, 8 rats were assigned to 1.5 atmospheres absolute (ATA) hyperbaric chamber 3 hours per day for one or 2 weeks (1WPG or 2WPG). Pain levels were assessed daily for 2 weeks according to weight bearing force (WBF) of the affected limb. In addition, the levels of gelatinase, MMP-2, and MMP-9 expression in synovial fluids of the knees were analyzed.ResultsThe reduction of WBF was high at one day after injection and then increased spontaneously up to 2 weeks in 1WPG and 2WPG. The pressure effects lasted for a given day and did not exceed the pressure effects of the next day in all study periods. Improvement of WBF in 2WPG was significantly greater than that of 1WPG during 8-14 days. The gelatinase expression ratio was significantly reduced in 1WPG and 2WPG, and 2WPG showed the lowest gelatinase ratio at 2 weeks.LimitationAlthough enough samples were used for the study, more samples will be needed to raise the reliability.ConclusionThe 3 hours of 1.5 ATA pressure effect lasted for more than a day. Longer pressure exposure time appears to yield a greater therapeutic effect in an RA animal model up to a given study period. Continuous application of high pressure might be beneficial for achievement of a better therapeutic effect in clinical application.

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