Ultrasound: evaluation of its mechanical and thermal effects.

Journal/Book: Arch-Phys-Med-Rehabil. 1984 May; 65(5): 223-7/Z. Physiother. 19 (1987) H. 4 212. 1984;

Abstract: Department of Physical Therapy Edmonton/Canada) AB: Despite the frequent clinical use of ultrasound (US) neither its effect on nerve conduction nor the explanation for these changes have been agreed upon. This study differentiated between the thermal and mechanical effects of US by using continuous US to provide combined mechanical and heating effects pulsed US to provide an equivalent mechanical effect placebo US to duplicate the pulsed US treatment and infrared radiation to provide a heating effect only. Ten subjects were randomly assigned to each of four treatment groups and the distal humeral segment of the ulnar nerve was treated. Statistically significant changes in both nerve conduction velocity (NCV) and subcutaneous tissue temperature were associated with each treatment. Continuous US and infrared radiation treatments were associated with increased temperatures (0.8C) and increased velocities (3.75 and 3.08m/sec respectively). Pulsed and placebo US treatments were associated with decreased temperatures (2.2C and 3.1C respectively) and decreased velocities (2.79 and 5.38m/sec respectively). Similar levels and patterns for NCV and subcutaneous tissue temperature were observed for the continuous US and the infrared groups and for the pulsed US and the placebo US groups. Additionally placebo US and infrared radiation treatments produced opposite temperature and velocity changes while not contributing any mechanical effects. It was concluded that the mechanical effects of US were not significantly operative in this study. The increased velocities associated with continuous US and infrared radiation treatments were attributed to a thermal-heating effect and the decreased velocities associated with placebo and pulsed US treatments were attributed to a thermal-cooling effect of the US transmission gel. Zusammenfassung/U. Smolenski (Jena) Differenzierung und Wertung der thermischen und mechanischen Wirkung des Ultraschalls sind derzeit problematisch. In der vorliegenden Arbeit werden Ultraschall in kontinuierlicher und pulsierter Form Infrarot sowie Placebo bei 40 Probanden appliziert. Die motorische Nervenleitgeschwindigkeit als Wirkkriterium zeigt eine deutliche Termperaturabhängigkeit mit Erhöhung bei Wärmewirkung (nach kontinuierlichem Ultraschall bzw. Infrarot) sowie Erniedrigung bei Abkühlung (nach pulsiertem Ultraschall bzw. Placebo). Bei der vorliegenden Untersuchung kann eine differente mechanische Wirkung auf die Nervenleitgeschwindigkeit zwischen kontinuierlichem Ultraschall (1 5 W/cm2 über 25 min Tastverhältnis 1:5) nicht nachgewiesen werden. Mechanische Effekte werden bei diesem Untersuchungsmodell wahrscheinlich durch die ausgeprägte thermische Wirkung überdeckt. hl

Keyword(s): Adult-; Evaluation-Studies; Infrared-Rays; Skin-Temperature; Time-Factors; Ulnar-Nerve-physiology

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