Superficial Cold And Heat Application During Transcutaneous Electrical Stimulation May Not Change Perceived Sensation Of Pain

Transcutaneous electrical stimulation is commonly applied in clinical practice to provide pain relief. Due to the discomfort associated with high intensity electrical stimulation, cold or heat is often applied to the area to allow higher stimulus intensity based on suggestions that the application of cold or heat alters the sensory pain perception through sensory nociceptive pathways. It is therefore of clinical relevance to investigate whether application of superficial heat or cold changes perceived pain sensation as a function of stimulation threshold. Twenty-six participants volunteered for this study. Constant voltage electrical stimulation with a frequency of 5 Hz, and a pulse width of 300 microseconds was applied to the tibialis anterior. The intensity of the electrical stimulation varied from zero to 200 volts peak to peak. Participants were requested to state when they first perceived any sensation of the electrical stimulation and when stimulus intensity became intolerable. Paired t-test analysis indicated no significant difference in the baseline peak current and the peak current following the application of either superficial heat or cold at the sensory threshold or limit of tolerance. There was a significant difference in the plateau current at baseline compared to the plateau current following the application of superficial heat and cold at the sensory threshold and limit of tolerance. From the experimental results this finding appears to be an artefact of altered skin impedance resulting from changing skin temperature. Thus, it is unlikely that the application of superficial heat or cold significantly changes the way transcutaneous electrical stimulation normally interacts with the sensory or pain systems.