Metrological Characterization of Therapeutic Devices for Pressure Wave Therapy: Force, Energy Density, and Waveform Evaluation

Pressure wave therapy is widespread for multiple purposes, from cell metabolism stimulation to tendons, ligaments, muscles, and bones pathologies treatment. However, in the literature, there are no quantitative metrological data related to pressure wave devices. On the contrary, it would be extremely important to have more information on the provided therapeutic signal, which could also be exploited as input for a finite-element model able to foresee the pressure wave propagation inside the tissues. The authors investigated three different versions of the same device in terms of force applied to the tissue. The results show high variability of the pulses intensities (up to 25%), highlighting a nonuniformity of the treatment (in particular at low frequencies and high compressed air pressure). Moreover, the dependence from different parameters (i.e., pulse frequency, pressure, opening time of the solenoid valve for the compressed air pushing the bullet) was investigated. It was found that the lower the frequency and the higher the opening time of the valve, the higher the force applied to the tissue. An estimation of energy density was done; sometimes the limit values provided by pressure wave therapy guidelines (i.e., DIGEST and ISMST) are exceeded, in particular for soft tissues.