4 - Superficial Thermal Agents and Modes of Heat Transfer

What is thermotherapy?

The therapeutic application of heat

What are the effects of heat application?

• INC vasodilation

• INC nerve conduction

• INC pain threshold

• DEC mm strength and tone

• Inc metabolic rate

• INC collagen extensibility

Vasodilation effects of heat application

• Works at the sit and systemically

• Via the direct reflex activation of smooth mm

• Indirectly activates local spinal cord reflexes

• Causes release of chemical mediators of inflammation

Neuromuscular effects of heat application

• Inc nerve conduction and DEC firing rate of type 2 mms (for every 1.8F inc, 2m/sec inc in velocity)

• Increased pain threshold (gate control, reduction ischemia and mm spasm)

• Decrease in muscle strength (only 30 mins after application)

How does heat affect metabolic rate?

Increases metabolic rate

Heat increases collagen extensibility.

True, heat alters tissue (collagen) extensibility making it more pliable and reducing the risk of tissue tear

General indications for various thermotherapies

• Pain control (gt control, reduced mm spasm)

• Increased range of motion and decreased joint stiffness (INCREASED EXTENSIBILITY)

• Accelerate healing (inc circulation and enzymatic activity)

• IR is used for psoriasis

General contraindications for various thermotherapies

• Recent or potential hemorrhage

• Thrombophlebitis

• Impaired sensation

• Impaired mentation

• Malignant tumor

• IR irradiation of the eyes

Precautions for thermotherapy

• Acute injury or inflammation

• Pregnancy

• Impaired circulation

• Poor thermal regulation

• Edema

• Cardiac insufficiency

• Metal in an area

• Open wounds

• Are where there is topical counterirritants

What is the temperature of the hydrocollator hotpacks are stored in?

158-167 F

Where should MHPs not be applied to on pregnant woman?

Trunk, hip, and groin area

How many layers of towels should be used with MHPs?

6-8

What must be done if applying a MHP a patient will be lying on in supine or leaning back on in sitting?

Wrap the MHP in extra layers to prevent burning

Paraffin

• Mixed with mineral oil to reduce the melting temp

• Applied to the skin between 113-122 dgs

• It can be dipped, wrapped, or painted on

• Wrapped with towels for insulation

• Not used on open wounds

What should the temperature of paraffin be?

113-122 F

Fluidotherapy

• Dry heating agent

• Heat transfer through convection

• Heated air circulated through ground cellulose particles (main substance in corn husks)

• Temp is set 100-118 dgs

• Combined with ROM

• Normal treatment time is 20 min

What type of heat transfer does fluidotherapy use?

Convection

AROM is often combine with fluidotherapy.

True, it can add to the beneficial effects

What temp should fluidotheray be used at?

100-118 F

Infrared lamp

• Emits electromagnetic radiation

• Absolute contraindication is pregnancy, cancer

• Reduces pain for chronic low back pain, stretching, and contractures

• Treatment time is 15-30 mins

Contrast bath

• Alternating between 100-111 dgs and 50-64 dgs

• Caused alteration between vasoconstriction and dilation

• Varies stimulation between pain relief and desensitization

• 3-4 min warm water, 1 min cool for 4-5 sequences and a total of 25-30 mins

What is the ration of warm to cool used with contrast bath?

3-4 mins warm then 1 min cool (4:1)

What temp should contrast baths be between?

50-64F and 100-111F

What is contrast bath used for?

• Chronic edema because alternatind warm and cool causes alternating vasodilation and vasconstrition that pushes edema out

• Subacute trauma

• Hypersensitivity

• Inflammatory conditions

If using contract for hyper sensitivity vs.. pain/edema, how are the temperatures different?

Hypersensitivity = smaller temp difference, pain/edema = larger temp difference

What does heat do to blood vessels and flow?

Causes vasodilation and increases blood flow

What are the best modalities to heat deep muscles?

Ultrasound and diathermy

Heat therapy can inc the pain threshold and dec the sensation of pain.

True

Muscle length should be tested before cold or heat therapy.

True

Heat decreases the local metabolic rate and therefore can lessen inflammation.

False

Heat will limit tissue extensibility when stretching.

False

Diabetes is not precaution when using heat therapy.

False

Specific heat

• The amount of energy required to raise the temperature of a given weight of a material by a given number of degrees

• Materials with more require more energy and hold the energy for longer

What is the specific heat of water?

4.19 joules per gram per degrees Celsius (J/g^oC)

Conduction

• Heat transfer resulting from energy exchange by direct collision between molecules of two materials at different temperatures; heat is transferred when materials are in contact with one another

• Materials have to be a different temps

• Ex. ice pack, paraffin, hot pack

Thermal conductivity

The rate at which a material transfers heat by conduction

Convection

• Heat transfer through direct contact of a circulating medium with a material of a different temperature

• Circulation of blood in the body uses this concept to help maintain the local temperature of the body to reduce the risk of thermal injury

• Ex. whirlpool, fluidotherapy

Conversion

• Heat transfer by conversion of a non-thermal from of energy such as mechanical, electrical, or chemical energy into heat

• Ex. diathermy (vibration of molecules), ultrasound (rotation, friction between molecules)

Radiation

• The transfer of energy from one material without the need for direct contact or an intervening medium

• Ex. infrared lamps

Evaporation

• A material absorbs energy and changes from a liquid to a gas or vapor

• Ex. Vapocoolant spray

Materials with high specific heat require more energy to heat up and hold more energy at a given temp (than materials with low specific heat)

True