Physical Considerations for In Vitro ESWT Research Design

Abstract

In vitro investigations, which comprise the bulk of research efforts geared at identifying an underlying biomechanical mechanism for extracorporeal shock wave therapy (ESWT), are commonly hampered by inadequate descriptions of the underlying therapeutic acoustical pressure waves. We demonstrate the necessity of in-situ sound pressure measurements inside the treated samples considering the significant differences associated with available applicator technologies and cell containment. A statistical analysis of pulse-to-pulse variability in an electrohydraulic applicator yields a recommendation for a minimal pulse number of n = 300 for cell pallets and suspensions to achieve reproducible treatments. Non-linear absorption behavior of sample holders and boundary effects are shown for transient peak pressures and applied energies and may serve as a guide when in-situ measurements are not available or can be used as a controllable experimental design factor. For the use in microbiological investigations of ESWT we provide actionable identification of common problems in describing physical shockwave parameters and improving experimental setups by; (1) promoting in-situ sound field measurements, (2) statistical evaluation of applicator variability, and (3) extrapolation of treatment parameters based on focal and treatment volumes.

Shockwaves Increase In Vitro Resilience of Rhizopus oryzae Biofilm under Amphotericin B Treatment

“…The application of large mechanical sheer/stretch forces on the biofilm leads to a disruption of the hyphae structure, resulting in a disintegration of the biofilm when applying high-pressure shockwaves. This is associated with the tensile part of the wave pulse, which is amplified when the pulse reflects at a fluid−air interface in the vicinity of the to-be-treated sample [ 29 ]. A similar, yet smaller destructive effect can be seen on the biofilm when exposed to lower-pressure shockwaves, as evidenced by a lower cellular viability immediately after treatment.…”