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Categories of Physical Agents (3)
How do thermal agents work?
They transfer energy to a patient to produce an increase or decrease in tissue temperature
Three types of thermal agents
- Deep heating
- Superficial heating
How do mechanical agents work?
They apply a force to the body that may increase or decrease pressure on a given structure or structures
Four types of mechanical agents
- Traction (pulling)
- Compression (pushing)
- Water (may be thermal)
- Sound (may also be thermal)
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.
Three Types of Electromagnetic Agents
- Shortwave diathermy (also thermal)
- Ultraviolet (sun)
- Electric Stimulation (alternating & direct current)
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
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.
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.
How are physical agents used?
In conjunction with exercise, functional activites and patient education programs
Four effects of Physical Agents
Know which are more common
- Modify inflammation and healing
- Relieve pain
- Alter Collagen Extensibility
- Modify muscle tone
How do physical agents affect inflammation and healing?
They act to reduce the effects of prolonged inflammation
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)
How are Beta receptors stimulated?
Light touch & heat (massage & ultrasound)
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.
The effect of thermal agents on collagen extensibility
Increased tissue temperature makes shortened tissues easier to stretch
- 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.
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
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
Which organ is the most involved in temperature regulation?
Central regulatory structure that responds to the neural input related to temperature regulation
Mechanisms of heat exchange (5)
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
- 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
-what are the 2 types and how do we utilize each type
- Superficial: Hotpacks, warm wirlpool, fluidotherapy, parafin
- Deep: Continuous ultrasound, short wave diathermy
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
Two levels of heating
- Mild: when tissue temperatures increase less than 40oC
- Vigorous: when tissue temperatures increase 40o-45oC
What is the risk involved with therapeutic heating using increased temperatures of more than 45oC?
The potential to cause serious pain & tissue damage
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
What have we noticed about deep heating modalities in particular?
They may cause a decrease in neural activity resulting in decreased muscle activity.
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)
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--160oPacks 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 126oTransfers 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
-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
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
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--
Methods of Cold Application
- Ice Massage
- Cold Pack (commercial/ice pack)
- Cold/Ice Bath (can be done in whirlpool)
-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
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
which is used when ROM impairments are primary & why?
Heat because it has a favorable effect on tissue extensibility
which have shown benefit for muscle guarding?
Both-- if one is ineffective, the other may be indicated
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