Cooling effects of Deep Freeze Cold Gel compared to that of an ice pack applied to the skin

In this study we report a comparison of ice packs applied to the lumbar spine of normal subjects for 10 minutes compared to a cold gel (Deep Freeze Cold Gel) applied to the same area on another day for 60 minutes. The subjects were examined in the prone position, lying on a couch in a temperature-controlled room at 22°C. After 15 mins stabilisation thermograms were recorded until no further temperature changes were evident. The 10×10cm ice pack or gel was applied to the skin at the L4 level. The Thermographic Camera Flir SC500 was stand mounted above the subject in a vertical position. Automatic software CTHERM) was used for image capture at 3 minute intervals for a further 60minutes. Subjective assessments were also recorded from each volunteer through the examination. Results showed that although a lower skin temperature was reached with ice (mean fall of 7°C) the temperature recovered quickly within 20 minutes. The gel applied to a 10×10 cm area of the lumbar region showed a more gradual fall in temperature (mean fall approx. 3.5°C) but this persisted for most of the 60 minute application. After 50 minutes there was a slow rise in temperature towards baseline. This study demonstrates that quantitative thermal imaging is a simple and objective tool for the evaluation of topical cooling treatments. It is however important to assess the emissivity of any applied substance which could have a significant effect on temperature measurement by remote sensing.