The Basic Physics of Waves, Soundwaves, and Shockwaves for Erectile Dysfunction

Abstract

Over the past decade, low-intensity extracorporeal shockwave therapy (Li-ESWT) has emerged as a treatment modality for erectile dysfunction (ED). To better appreciate the differences between the various devices for the treatment of ED, it is imperative for physicians to understand the underlying physics of the different shockwave generators. In this article, we explain the physics of shockwaves by establishing a foundation regarding the basics of waves, specifically soundwaves. We also describe the different shockwave generators available and assess their potential clinical utility. We reviewed basic principles of wave propagation, randomized controlled trials investigating Li-ESWT for ED and other medical diseases, and individual industry shockwave generator websites, in order to describe the basic physics underlying Li-ESWT. We primarily aimed to describe the physics underlying shockwave generators and to provide a framework for understanding the relevant subtypes and adjustable parameters. A wave is a disturbance in a medium that transports energy without permanently transporting matter. In shockwaves, a soundwave is generated with a speed faster than the local speed of sound. Shockwaves are classically generated by three different types of energy sources: electrohydraulic, electromagnetic, or piezoelectric, which all create a shockwave through the conversion of electric potential energy to mechanical energy. Importantly, radial pressure waves do not behave the same as conventional shockwaves and are more like "ordinary" sound waves in that they achieve a significantly lower peak pressure, a slower rise time, and propagate outwards without a focal point. Li-ESWT is not currently approved by theU.S. Food and Drug Administration and is considered investigational in the United States. However, it is currently available to patients under clinical trial protocols and it is important to understand the basic physics of shockwaves to understand the differences between the different shockwave devices. This is a comprehensive review of the physics underlying Li-ESWT but only tangentially explores the biological impact of shockwaves. Physicians currently using or those contemplating purchasing a Li-ESWT device should understand the basic physics underlying the device, as well as which treatment protocols were used to demonstrate clinical efficacy in treating ED. Katz JE, Clavijo RI, Rizk P, etal. The Basic Physics of Waves, Soundwaves, and Shockwaves for Erectile Dysfunction. Sex Med Rev 2020;8:100-105.