Supriya Babu

Topics Physical basis of heat and cold Measurement of temperature: Thermometry Mapping of body’s surface temperature: Thermography Heat Therapy and uses of cold in medicine

States of Matter Solids Gases Vibrations Kinetic Energy of molecules associated with temperature

Measurement of Temperature Indirectly by measuring the change in a physical quantity that changes with temperature Different temperature scales

Construction of Thermometer Principle: Differential Expansion of materials 1cm 3 of mercury increases in volume when temperature changes from 0  C to 100  C Smaller the diameter of capillary greater the sensitivity: 0.1mm Visibility is increased by Cross section of Thermometer Capillary Lens Front White Backing

Temperature Sensitive Devices Thermistor Thermocouple

Variation in body temperature External factors Internal – Metabolic – Circulatory (Major) Far Infrared (IR) Stefan-Boltzmann law – W = e  T 4  = 5.7 x W/cm 2  K 4

Thermographic Unit

Diathermy diathermy [di´ah-ther ″ me] means "electrically induced heat" the use of high- frequency electromagnetic currents Greek words dia and therma, and literally means “heating through. short-wave radio frequency (range 1– 100 MHz) Microwave energy (range 434–915 MHz)

SHORTWAVE DIATHERMY SWD

Description High-frequency electrical currents – Radio waves Pass through the tissues Cause molecular vibration Results in deep heating Capable of heating large volumes of tissues Causes both thermal and non-thermal effects

Uses Thermal Effects Deep heat Increased blood flow Increased cell metabolism Increased tissue extensibility Muscular relaxation Possible changes in enzyme reactions Non-thermal Effects Edema reduction Lymphedema reduction Superficial wound healing Treatment of venous stasis ulcers

Types of Shortwave Diathermy Induction Field Capacitive Field

Induction Field Diathermy Places the patient in the electromagnetic field Selectively heats muscle Also referred to as: – Condenser field diathermy – Magnetic field diathermy

Induction Field Diathermy (Cont.) A coil is housed within a drum Current flowing within the coil produces a rotating magnetic field Magnetic field produces eddy currents in the tissues Eddy currents cause friction that produce heat Although rare, cables are sometimes used in place of drums

Capacitive Field Diathermy Uses the patient’s tissues as a part of the circuit The tissues’ electrical resistance produces heat Selectively heats skin – Muscle is heated via conduction from the adipose Also referred to as “condenser field diathermy”

Capacitive Field Diathermy (Cont.) Heat is produced by the dipole effect Charge particles within membrane align with the field The movement produces heat

Modes of Application Continuous Increases tissue temperature Increased risk of burns Pulsed May or may not increase temperature Pulses allow for increased treatment intensity and duration Not the same as “non-thermal”

Ultrasound & SWD Comparison Diathermy UltrasoundShortwave Energy typeAcousticalElectromagnetic Tissue heatedCollage-richC: Skin, adipose tissue I: Muscle, vessels Tissue volumeSmall (20 cm 2 )Large (200 cm 2 ) Temp increase1 MHz: > 6.3°FC: > 7°F 3 MHz: > 14.9°FI: > 18°F Heat retention3 min> 9 min C = Capacitive method I = Induction method

Biophysical Effects Inflammation Assists in removal of cellular debris and toxins Non-thermal: – Alters diffusion rate across the cell membrane Thermal – Increases intramuscular metabolism

Biophysical Effects Blood and Fluid Dynamics Vasodilation increases: – Blood flow – Capillary filtration – Capillary pressure – Oxygen perfusion Effects occur deeper than other forms of heat

Biophysical Effects Tissue Elasticity SWD can vigorously heat deep tissues Alters collagen properties, allowing it to elongate Requires stretching during and/or immediately following the treatment Multiple treatments are required

Contraindications Metal implants or metal jewelry Cardiac pacemakers Ischemic areas Peripheral vascular disease Perspiration and moist dressings: The water collects and concentrates the heat. Tendency to hemorrhage, including menstruation. Pregnancy Fever Sensory loss Cancer Areas of particular sensitivity: – Epiphyseal plates in children – The genitals – Sites of infection – The abdomen with an implanted intrauterine device (IUD) – The eyes and face – Application through the skull