Background: We 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.
Objective: We evaluated the duration of the pressure effect in a day for a given study
period.
Study Design: Laboratory animal study.
Methods: Following 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.
Results: The 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.
Limitation: Although enough samples were used for the study, more samples will be
needed to raise the reliability.
Conclusion: The 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.
Key words: Pressure effect, arthritic knee, arthritic pain, long-term effect of pressure,
biophysiologic assessment, pain behavior assessment, arthritis treatment
The Continuance Time of Pressure Effect in
the Rat Model of Complete Freund’s Adjuvant
Induced Arthritis
