Effects of 1 MHz Therapeutic Ultrasound on Limb Blood Flow and Microvascular Reactivity: A Randomized Pilot Trial.

Megan Waters,Branko Miljkovic,Jozelyn Rascon,Manuel Gomez,Alvaro N Gurovich

doi:10.3390/ijerph182111444

Abstract

A randomized, double-blind, placebo-controlled, cross-over study where continuous therapeutic ultrasound (CUS; at 0.4 W/cm2), pulsed therapeutic ultrasound (PUS; at 20% duty cycle, 0.08 W/cm2), both at 1 MHz, and placebo (equipment on, no energy provided) were randomized and applied over the forearm of the non-dominant arm for 5 min in 10 young, healthy individuals. Absolute and peak forearm blood flow (FBF) were measured via Venous Occlusion Plethysmography. FBF was measured before, halfway, and after (immediately and 5 min after) the therapeutic ultrasound (TUS) intervention. Post-ischemic peak FBF was measured 10 min before and 10 min after the TUS intervention. A two-way repeated measures ANOVA (group × time) was selected to assess differences in FBF before, during, and after TUS treatment, and for peak FBF before and after TUS treatment. FBF increased 5 min after TUS in CUS compared to placebo (2.96 ± 1.04 vs. 2.09 ± 0.63 mL/min/100 mL of tissue, p < 0.05). PUS resulted in the greatest increase in Peak FBF at 10 min after US (Δ = 3.96 ± 2.02 mL/min/100 mL of tissue, p = 0.06). CUS at 1 MHz was an effective treatment modality for increasing FBF up to 5 min after intervention, but PUS resulted in the greatest increase in peak FBF at 10 min after intervention.

Highlights

The results found that, in healthy volunteers, continuous therapeutic ultrasound (CUS) might increase microvascular blood flow after the therapeutic ultrasound (TUS) application and that pulsed therapeutic ultrasound (PUS) increased peak vascular reactivity, which is associated with an increase in endothelial function and nitric oxide (NO) bioavailability
Even though the present study showed a decrease in forearm blood flow (FBF) during the intervention (Figure 2), CUS produced a rebounce on blood flow 5 min after the intervention
This finding could be explained by two reasons: (1) as the upper extremity during VOP needs to be elevated during the assessment of blood flow, subjects kept their forearm in that position for the total time of the study; there might be some decrease in blood flow due to gravity and (2) the re-bounce of blood flow is a clear effect of CUS enhancing blood flow even with gravity affecting it

Summary

Introduction

Musculoskeletal injuries are typically associated with tissue damage, pain, and inflammation [1]. Resolution of soft tissue damage relies on endothelium-dependent blood flow to deliver essential cellular components and healing factors [2]. Vascular endothelial cells play a key role in regulating local blood flow and maintaining vascular integrity through the production of nitric oxide (NO) in response to physical or chemical stimuli [3,4]. NO regulates vascular tone and permeability, inhibits platelet aggregation, and stimulates angiogenesis [4,5,6,7]. NO synthesis during tissue healing has a positive clinical implication as it promotes aforementioned essential components required for maintaining hematological stasis around the injured tissue [1]

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