Preliminary studies on the effects of laser irradiations on nerve injuries caused by high frequency electrical stimulations

Nerve conduction blocking by high frequency biphasic (HFB) electrical stimulations would cause injuries to nerves. This study aimed to investigate whether laser irradiations could reduce this kind of injuries as an assistant method. Compound action potentials (CAPs) were recorded on isolated bullfrog's sciatic nerve before and following HFB electrical stimulations in each experimental trial, and the laser irradiations of 650 nm or 850 nm at various power were applied in testing trials. The parameters of injury rates and effectiveness ratios were computed from the CAPs to identify how many axons were influenced in respect of conductibility and how effective the laser irradiations were for the neural recoveries. The results showed that the laser irradiations of 650 nm and 75 mW reduced nerve injury rates following HFB electrical blocking stimulation and improved neural recovering speed by an average rate of 0.145. With the power of 50 mW, the 650 nm laser irradiation resulted in more significant (P<0.0001) effectiveness ratio than the 850 nm laser irradiation in reducing the nerve injuries. Lasers of different power seemed to act effectively at different irradiating time lengths. The 25 mW laser irradiation displayed the shortest latency to begin to work and the longest effective duration, while the 75 mW laser irradiation exhibited the most significant overall performance. As an assistance method, laser irradiations could effectively reduce the nerve injuries caused by HFB electrical stimulations and would promote the clinical applications of it.