Physical Agents 10/3/11 lecture 1
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Physical Agents 10/3/11 lecture 1
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
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
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)
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
Modify inflammation and healing
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
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
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
: Hotpacks, warm wirlpool, fluidotherapy, parafin
: 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
: when tissue temperatures increase less than 40
: when tissue temperatures increase 40
What is the risk involved with therapeutic heating using increased temperatures of more than 45
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
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--
Packs are covered w/
of towel before placement on the patient
mineral oil and parafin wax
that is maintained in thermostatically controlled "bath" at approximately
Transfers heat by CONDUCTION
distal extremities--primarily the hand
Viewed by some as recreational
contain particles of natural cellulose enclosed in a cabinet through which warm dry air flows
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
--cool whirlpool (uncommon)
Short Term vs. Long Term effects of cold
of the superficial blood vessels
: hypothalamus responds with
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
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