title: Short-term sensory and cutaneous vascular responses to therapeutic ultrasound in the forearms of healthy volunteers.
abstract: BACKGROUND
  Therapeutic 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/cm(2), 5 min; 1 MHz, continuous, 0.8 W/cm(2), 3 min), on sensory and vascular responses in the healthy forearms.
  
  
  METHODS
  Twenty 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.
  
  
  RESULTS
  Both 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).
  
  
  CONCLUSIONS
  This 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.
authors.affiliation: Faculty of Health Sciences, Department of Health and Rehabilitation Sciences, Physical Therapy Field, Western University, London, ON N6G 1H1, Canada.
authors.forename: Shaguftha Sultana
authors.initials: SS
authors.lastname: Shaik
authors.affiliation: Faculty of Health Sciences, Department of Health and Rehabilitation Sciences, Physical Therapy Field, Western University, London, ON N6G 1H1, Canada ; Hand and Upper Limb Centre, Clinical Research Laboratory, St. Joseph's Health Centre, London, ON N6A 4 V2, Canada ; School of Rehabilitation Science, McMaster University, Hamilton, ON L8S4L8, Canada.
authors.forename: Joy C
authors.initials: JC
authors.lastname: MacDermid
authors.affiliation: Tier 2 Canada Research Chair in Musculoskeletal Rehabilitation, Faculty of Health Sciences, Department of Health and Rehabilitation Sciences, School of Physical Therapy, Western University, London, ON N6G 1H1, Canada.
authors.forename: Trevor
authors.initials: T
authors.lastname: Birmingham
authors.affiliation: Hand and Upper Limb Centre, St. Joseph's Health Care, Division of Orthopedics, Western University, London, ON N6A 4 L6, Canada.
authors.forename: Ruby
authors.initials: R
authors.lastname: Grewal
authors.affiliation: Physiotherapist, London, ON N6G 1H1, Canada.
authors.forename: Baseer
authors.initials: B
authors.lastname: Farooq
keywords: Forearm; Sensory perception threshold; Skin blood flow; Skin temperature; Ultrasound