1 / 19

Thermal Modalities

Thermal Modalities. General Principles. Physical Laws. Cosine Law Inverse Square Law Arndth-Schultz Principle Law of Grotthus-Draper. Cosine Law. Angle of incidence: The angle at which radiant energy strikes the body.

carrington
Download Presentation

Thermal Modalities

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Thermal Modalities General Principles

  2. Physical Laws Cosine Law Inverse Square Law Arndth-Schultz Principle Law of Grotthus-Draper

  3. Cosine Law • Angle of incidence: The angle at which radiant energy strikes the body. • As the angle of incidence changes from 90º, the less effective the transmission. • Based on the cosine of the angle of incidence: • Effective energy = Energy * Cosine (angle) • Radiant energy should be ±90º

  4. Inverse Square Law • Intensity of radiant energy depends on the distance between the source and the target. • Changing the distance changes the intensity • Change is proportional to the square of the distance.

  5. Inverse Square Law • Formula: E = Es/D2 E – energy received by the tissue Es – energy produced by the source D2 – Square of the distance between the target and the source • Doubling the distance between the tissues and the target decreases the intensity by a factor of four.

  6. Arndth-Schultz Principle • Energy must be absorbed by the tissues • Must be sufficient to stimulate a physiological response • Too little stimulus: no effect • Too much stimulus: injury

  7. Grotthus-Draper • Inverse relationship between absorption and penetration of energy. • Energy absorbed by one tissue layer is not passed along to deeper layers. • The more energy absorbed in superficial layers, the less available for deeper layers.

  8. General Physiology

  9. Metabolic Changes • Heat increases metabolism • Cold decreases metabolism • A 1.8ºF (1ºC) change in tissue temperature = 13% change in metabolism

  10. Tissue Properties • Deeper tissues have higher temperatures • Different tissues have different conductivity properties Thermal Conductivity • Skinc 0.96 • Adipose Tissuei 0.19 • Musclec 0.64 c – conductor i - insulator

  11. Thermoreceptors • Cold-responsive receptors • Heat-responsive receptors • More cold receptors than heat receptors

  12. Physics

  13. General Principles • Exchange of kinetic energy (heat) • Transfer of energy is based on a gradient between two points • The greater the gradient, the more energy that is transferred • Energy always moves from a high concentration to a low concentration • Moist heat pack to the skin • Skin to an ice pack

  14. Transfer of Thermal Energy Conduction Convection Radiation Evaporation Conversion

  15. Conduction • Objects are touching each other • Conductors • Skin • Muscle • Insulators • Adipose tissue • Terrycloth towels

  16. Convection • Involves the circulation of air or water • One object is cooled • Another object is heated • Example: • Whirlpool

  17. Radiation • No medium is required • Examples: • LASER • Infrared light • Ultraviolet light • Thermal modalities provide radiant energy • But is not the primary form of heat exchange

  18. Evaporation • Change from liquid to gaseous state • Draws heat from the body • Cools superficial tissues • Examples: • Sweating • Vapocoolant sprays

  19. Conversion • Change of one form of energy to another • Electromagnetic energy to heat • Acoustical energy to heat • Examples: • Short wave diathermy • Ultrasound

More Related