Effect of low-power laser therapy on edema dynamics: sensing by using the electrical capacitance method

Abstract

The inflammatory process can be considered as a tissue protective response to an aggressive stimulus. That process leads to an increase in vascular permeability and, consequently, edema formation. In this study it is shown that the electrical capacitance can be used as a tool for the monitoring of the time evolution of an edema in biological tissues and that the method can sense the modulating effect of low power laser therapy. The electrical capacitance was measured during the edema settling up in rats after induction of acute inflammation by carrageenan injections, associated or not with low power laser therapy. A LCR meter model LCR-815B from HP, was used to measure the electrical capacitance between two electrodes positioned onto the rat skin, in the edematous site. Measurements were taken every 15 min. All rats were anesthetized to overcome electrical capacitance variations. Rats were divided into three groups: i) only anesthetic was injected (0.3 ml of Zoletil 50); ii) anesthetic and 1 ml of carrageenin at 2%; iii) same as group (ii) plus treatment with 2.5 J/cm² from a GaAlAs laser (650 nm). A maximum on the capacitance variation was observed when the anesthetic and the carrageenin were injected. Lower values were obtained for the laser treated group, which corroborated with the anti-inflammatory effect of the laser therapy. The electric capacitance accompanied the settling up and down of the edemas for all animals.