System for application of contrast therapy and Transcutaneous Electrical Nervous Stimulation for pain treatment

There are two methods widely used by physiotherapists for pain treatment and rehabilitation purposes. These methods are: Thermal contrast therapy and Transcutaneous Electrical Nervous Stimulation (TENS). Thermal contrast therapy usually consists on the application of hot and cold pads over the site of interest during a determined period of time (usually less than 30 minutes). Sometimes, the hot and cold sessions are intercalated for better therapeutic results. The problem with the application of such therapy nowadays is that it is based on pads which must be heated or cooled by mean of external devices (ovens, hot bath and freezers) using energy during the whole day to keep the pads at the correct temperature ready for their use. Another problem is the loss of thermal energy of the pads during their use on the patient skin. Thus, if at the beginning of the therapy the cold (or hot) pad was at the right temperature, after few minutes the temperature will not be enough for the therapeutic result. Furthermore, usually these thermal therapies are applied simultaneously with TENS, thus the physiotherapist requires at least two devices, making their application cumbersome. This paper presents an electronic system for the application of heat or cold and TENS therapies simultaneously. Design and preliminary results on the characterization of the system are presented showing the viability of the proposal. Temperatures over the range of 8 °C - 50 °C were reached and maintained independently of the ambient temperature. TENS was generated with a voltage range of 10 - 50V and frequency from 1 - 300Hz and current output until 50 mA.