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Categories of Physical Agents (3)
- Thermal
- Mechanical
- Electromagnetic
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How do thermal agents work?
They transfer energy to a patient to produce an increase or decrease in tissue temperature
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Three types of thermal agents
- Deep heating
- Superficial heating
- Cooling
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How do mechanical agents work?
They apply a force to the body that may increase or decrease pressure on a given structure or structures
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Four types of mechanical agents
- Traction (pulling)
- Compression (pushing)
- Water (may be thermal)
- Sound (may also be thermal)
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How do Electromagnetic Agents work?
- Utilize electromagnetic radiation or electric currents to effect changes in body tissues
- cause vibration in body tissues to increase temp.
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Three Types of Electromagnetic Agents
- Shortwave diathermy (also thermal)
- Ultraviolet (sun)
- Electric Stimulation (alternating & direct current)
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What historical evidence supports the use of physical agents?
- References to the use of hot water and light--Greek & Roman writings
- Various popularities throughout centuries
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The position of the APTA in regard to physical agents
Without documentation justifying using physical agents without other treatment, this use of modalities should not be considered physical therapy.
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How are physical agents best used in most cases?
Part of a comprehensive treatment program that includes a number of intevetions designed to progress the patient toward their functional outcomes.
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How are physical agents used?
In conjunction with exercise, functional activites and patient education programs
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Four effects of Physical Agents
Know which are more common
- Modify inflammation and healing
- Relieve pain
- Alter Collagen Extensibility
- Modify muscle tone
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How do physical agents affect inflammation and healing?
They act to reduce the effects of prolonged inflammation
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Explain the relationship between physical agents and pain.
-How do they manage pain psychologically?
Physical agents may stimulate Beta receptors providing pleasant sensations that may act to block painful sensations (psychological effect to relax and releive tension)
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How are Beta receptors stimulated?
Light touch & heat (massage & ultrasound)
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How do physical agents affect the transmission of painful impulses to the spinal cord?
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.
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The effect of thermal agents on collagen extensibility
Increased tissue temperature makes shortened tissues easier to stretch
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Muscle Guarding/Spasm
- why do muscles guard/spasm
- how do thermal agents reduce guarding/spasm?
- 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.
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Muscle Tone (neurological concept0
-what is it?
-how do thermal agents affect it?
- The underlying tension that serves as the background for contraction in a muscle
- Thermal agents may alter the speed of nerve conduction velocity
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Practical Use of Physical agents
- 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
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Which organ is the most involved in temperature regulation?
The skin
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Hypothalamus
Central regulatory structure that responds to the neural input related to temperature regulation
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Mechanisms of heat exchange (5)
- Conduction
- Convection
- Radiation
- Conversion
- Evaporation
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Factors that may influence the intensity of temperature changed (4)
- Temperature difference between therapeutic agent and target tissue
- Time of exposure to thermal agent
- Tissue conductivity of target tissue
- Intensity of thermal agent
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Conduction
- Heat loss or gain through DIRECT CONTACT between materials of different temperatures
- EX) HOT PACK
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Convection
- 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
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Radiation
- Radiant energy transfers heat through the air from a warmer source to a cooler source
- EX) Infrared lamp (not in common practice)
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Conversion
- 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)
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Evaporation
- 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
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Therapeutic Heat
-what are the 2 types and how do we utilize each type
- Superficial: Hotpacks, warm wirlpool, fluidotherapy, parafin
- Deep: Continuous ultrasound, short wave diathermy
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Physiological changes in response to heat application vary according to... (3 things)
- The intensity of the heating agent
- The duration of application
- The area being treated
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Two levels of heating
- Mild: when tissue temperatures increase less than 40oC
- Vigorous: when tissue temperatures increase 40o-45oC
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What is the risk involved with therapeutic heating using increased temperatures of more than 45oC?
The potential to cause serious pain & tissue damage
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Physiological Effects of Heat
- 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
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What have we noticed about deep heating modalities in particular?
They may cause a decrease in neural activity resulting in decreased muscle activity.
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Describe the relationship between superficial heating agents and tissue temperatures
- 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)
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Important things to remember about HOT PACKS/Hydrocollator
- 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--160o
- Packs are covered w/ 6-8 layers of towel before placement on the patient
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Paraffin Bath
- Mixture of mineral oil and parafin wax that is maintained in thermostatically controlled "bath" at approximately 126o
- Transfers heat by CONDUCTION
- Used for distal extremities--primarily the hand
- Viewed by some as recreational
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Fluidotherapy
- 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
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Cryotherapy
-what is it?
-what are some forms that are used?
- The use of cold for therapeutic effects
- Cryotherapy agents include
- --cold packs
- --cool whirlpool (uncommon)
- --Ice massage
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Short Term vs. Long Term effects of cold
- Short term: vasoconstriction of the superficial blood vessels
- Long term: hypothalamus responds with vasodilation in an effort to maintain the temperature of critcal structures
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Effects of Cold
- 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--
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Methods of Cold Application
- Ice Massage
- Cold Pack (commercial/ice pack)
- Cold/Ice Bath (can be done in whirlpool)
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Contrast Bath
-what is it
-where is it used
-why was it thought to be important historically?
- 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
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Clinical Decision making between heat & cold (generalization--not a rule)
- which is used for chronic vs/ acute pain??
- Cold preferred for ACUTE injuries
- Heat preferred for CHRONIC pain
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Heat/Cold?
which is used when ROM impairments are primary & why?
Heat because it has a favorable effect on tissue extensibility
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Heat/Cold
which have shown benefit for muscle guarding?
Both-- if one is ineffective, the other may be indicated
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Why is neither heat nor cold better than the other for pateints as a whole?
- Patients often have a preference for one or the other.
- The patients perceived usefulness of the modality may impact the treatment effectiveness
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