Short-term sensory and cutaneous vascular responses to therapeutic ultrasound in the forearms of healthy volunteers

Abstract

BackgroundTherapeutic ultrasound (US) is used for a variety of clinical pathologies and is thought to accelerate tissue repair and help with pain reduction via its thermal and nonthermal effects. The evidence on physiological effects of US on both sensory and vascular functions in humans is incomplete. Hence, the purpose of this study was to determine the short-term impact of two doses of US (3 MHz, 1:4, 0.25 W/cm2, 5 min; 1 MHz, continuous, 0.8 W/cm2, 3 min), on sensory and vascular responses in the healthy forearms.MethodsTwenty healthy subjects were recruited (mean age, 29.6 ± 8.8 years) for the study. Superficial blood flow (SBF) in the distal forearms was determined using the tissue viability imaging system. Sensory perception thresholds (SPT) were determined from ring finger (C7, C8) to assess A-beta (at 2,000 Hz) and C fiber function (at 5 Hz), using a Neurometer CPT/C device. Subject’s two hands were randomly allocated to group order (AB/BA). Scores were obtained before and immediately after the application of US and control. Differences in these were analyzed using repeated measures.ResultsBoth 3 MHz pulsed US and 1 MHz continuous US showed small to moderate (effect size = 0.12 to 0.68), statistically significant reductions in SBF (3 MHz, mean change = 2.8 AU and 1 MHz, mean change = 3.9 AU, p < 0.05 respectively), skin temperature (2.5°C and 1.1°C, p < 0.05), and SPT at 5 Hz (1.3 and 1 mA, p < 0.05) across time. SPT at 2,000 Hz remained unaltered by all three conditions (p > 0.05). Age and gender also had no effect on all outcome measures (p > 0.05).ConclusionThis study demonstrated minor reductions in skin blood flow, skin temperatures, and C fiber perception thresholds immediately after 3 MHz, and 1 MHz US. The responses observed may have been due to a thermo-cooling effect of the gel or due to the direct effect of US on C fibers of median and ulnar nerves. US had a negligible effect on A-beta fibres. This would suggest that future studies looking at physiological effects of US should move towards investigating larger dosages and study the effects in patient populations.

Therapeutic ultrasound treatment for excessive skin on the upper arms due to extensive weight loss after bariatric surgery: A single blind, randomised, controlled trial

“…Even though we were not able to present any objective difference either before or after treatment on the treated arm or between the treated or non-treated arms, patients expressed symptom deburdening in terms of a change in skin consistency, skin pain relief, and decreasing inflammation processes such as skin bursts. It is known that ultrasound increases cutaneous blood perfusion [27,28], and this may be the reason for the positive responses from the patients. Hence, a positive result of ultrasonic treatment in other forms of loose skin may not be applied in this symptom context.…”

A comparison of blood flow changes in tissues treated with therapeutic ultrasound and electrical stimulation

“…In a study exploring muscle temperature, at 1MHz, 1.5 W/cm 2 and 2.0 W/cm 2 , the rate of temperature increase was so rapid that some of the participants were not able to complete the 10-minute treatment due to discomfort. 66 Shaik et al 54 used two treatment parameters on subjects: pulsed ultrasound at 3 MHz, 1:4 duty cycle, at an intensity of 0.25 W/cm 2 for 5 minutes and continuous ultrasound at 1 MHz, at an intensity of 0.8 W/cm 2 for 3 minutes. The results of this study found that there was a significant decrease in skin blood flow over the treatment area, comparing baseline to post-treatment measurements following both treatments.…”

“…The results of this study found that there was a significant decrease in skin blood flow over the treatment area, comparing baseline to post-treatment measurements following both treatments. 54 Skin blood flow was measured using a spectroscopy camera, examining the red blood cell concentration in dermal tissue. 54 Pulsed ultrasound at 3…”

“…3 Thermal effects can be achieved with continuous ultrasound and adequate intensity of the treatment. 54 Nonthermal effects of therapeutic ultrasound are more commonly desired in the early stages after injury. 53 Reports have found that nonthermal effects aid the immune response by inducing vasodilation of arterioles and activation of adhesion molecules, which are regulated by signal-transduction pathways.…”

“…The transducer had an effective radiating area (ERA) of 4.0 cm 2 and a beam non-uniformity ratio (BNR) of <4.0 and was calibrated before research began. 54 Five milliliters of an aqueous Aquasonic Clear ultrasound gel (Parker Laboratories, Inc, Fairfield, NJ) was used as the coupling medium and kept at room temperature. 68 Electrical stimulation was delivered by a 2-channel stimulator (ARISTA 2000, Eagle Medical, St. Louis, MO).…”