Physical Agents 10/3/11 lecture 1

• Thermal
• Mechanical
• Electromagnetic

They transfer energy to a patient to produce an increase or decrease in tissue temperature

• Deep heating
• Superficial heating
• Cooling

They apply a force to the body that may increase or decrease pressure on a given structure or structures

• Traction (pulling)
• Compression (pushing)
• Water (may be thermal)
• Sound (may also be thermal)

• Utilize electromagnetic radiation or electric currents to effect changes in body tissues
• cause vibration in body tissues to increase temp.

• Shortwave diathermy (also thermal)
• Ultraviolet (sun)
• Electric Stimulation (alternating & direct current)

• References to the use of hot water and light--Greek & Roman writings
• Various popularities throughout centuries

Without documentation justifying using physical agents without other treatment, this use of modalities should not be considered physical therapy.

Part of a comprehensive treatment program that includes a number of intevetions designed to progress the patient toward their functional outcomes.

In conjunction with exercise, functional activites and patient education programs

• Modify inflammation and healing
• Relieve pain
• Alter Collagen Extensibility
• Modify muscle tone

They act to reduce the effects of prolonged inflammation

Physical agents may stimulate Beta receptors providing pleasant sensations that may act to block painful sensations (psychological effect to relax and releive tension)

Light touch & heat (massage & ultrasound)

When there is a greater thermal (pleasant) stimuli than painful stimuli the transmission "gate" may be closed blocking the transmission of painful impulses to the spinal cord.

Increased tissue temperature makes shortened tissues easier to stretch

• Muscle guarding and spasm may result from high levels of motor unit firing in order to protect painful parts for further trauma
• Thermal agents have been shown to reduce this effect resulting in interruption of the pain spasm cycle.

• The underlying tension that serves as the background for contraction in a muscle
• Thermal agents may alter the speed of nerve conduction velocity

• Specific indications and contraindications are identified for each physical agent
• Precautions are also noted
• The clinician applying the treatment is responsible for the safe and effective application of that treatment

The skin

Central regulatory structure that responds to the neural input related to temperature regulation

• Conduction
• Convection
• Radiation
• Conversion
• Evaporation

• Temperature difference between therapeutic agent and target tissue
• Time of exposure to thermal agent
• Tissue conductivity of target tissue
• Intensity of thermal agent

• Heat loss or gain through DIRECT CONTACT between materials of different temperatures
• EX) HOT PACK

• The transfer of het by the MOVEMENT OF WATER, AIR, OR LIQUID around the body part in question
• EX) FUIDOTHERAPY & WHIRLPOOL

Fluidotherapy--used for upper extremity

• Radiant energy transfers heat through the air from a warmer source to a cooler source
• EX) Infrared lamp (not in common practice)

• Temperature change that occurs when one form of energy is changed to another form of energy releasing heat in the process
• EX) continuous ultrasound (mechanical energy turns to heat)

• Changes in temperature and heat release that result from the trasformation of a material from a liquid state to a gas state
• EX) vapocoolant spray

• Superficial: Hotpacks, warm wirlpool, fluidotherapy, parafin
• Deep: Continuous ultrasound, short wave diathermy

• The intensity of the heating agent
• The duration of application
• The area being treated

• Mild: when tissue temperatures increase less than 40^oC
• Vigorous: when tissue temperatures increase 40^o-45^oC

The potential to cause serious pain & tissue damage

• Increased tissue temperatures--> leads to increased blood flow to the area
• Increased temperature of local tissues
• May BLOCK transmissions of PAINFUL STIMULI to the brain
• Reduction in muscle guarding
• Tissue Extensibility

They may cause a decrease in neural activity resulting in decreased muscle activity.

• Heat from superficial agents generally penetrate less than 2cm from the surface of the skin
• Underlying tissue temperatures may increase due to conductions from superficial tissues (step system)

• Various sizes & shapes
• Made of silical gel in a channeled canvas pack; transfers heat by conduction
• Maintained in a continuous bath of thermostatically controlled water--160^o
• Packs are covered w/ 6-8 layers of towel before placement on the patient

• Mixture of mineral oil and parafin wax that is maintained in thermostatically controlled "bath" at approximately 126^o
• Transfers heat by CONDUCTION
• Used for distal extremities--primarily the hand
• Viewed by some as recreational

• Units that contain particles of natural cellulose enclosed in a cabinet through which warm dry air flows
• Heat is maintained as a steady temperature through the treatment unlike hot packs and paraffin which loose heat
• Patient can exercise while in the unit

• The use of cold for therapeutic effects
• Cryotherapy agents include
• --cold packs
• --cool whirlpool (uncommon)
• --Ice massage

• Short term: vasoconstriction of the superficial blood vessels
• Long term: hypothalamus responds with vasodilation in an effort to maintain the temperature of critcal structures

• Edema & muscle spasm Reduction
• Management of acute inflammation resulting from trauma
• Effectiveness improved w/ compression-- RICE
• Pain Reduction-- inhibiting sensory receptors/counter irritant
• Reduction of spasticity resulting from CNS abnormalities
• --Inhibition of spasticity may have positive impact on functional mobility--

• Ice Massage
• Cold Pack (commercial/ice pack)
• Cold/Ice Bath (can be done in whirlpool)

• Alternate application of superficial heat with cold via an immersion bath
• Rare in clinical practice though some patients find it helpful
• Can easily by done at home
• Historically though to provide "vascular exercise" that was beneficial to musculoskeletal pain

• Cold preferred for ACUTE injuries
• Heat preferred for CHRONIC pain

Heat because it has a favorable effect on tissue extensibility

Both-- if one is ineffective, the other may be indicated

• Patients often have a preference for one or the other.
• The patients perceived usefulness of the modality may impact the treatment effectiveness