thermal agents cold and heat Flashcards
Modes of Heat Transfer
- conduction
- convection
- conversion
- radiation
- evaporation
Conduction
- energy exchange through direct contact
Rate of heat transfer=
area of contact x thermal conductivity x temperature difference= tissue thickness
convection
heat transfer by direct contact of circulating medium and another material of different temperature
- thermal agent is in motion
- more efficient than conduction.
- EX: whirlpool heats skin faster than if just immersed in a bowl of water of same temp
examples of convection
- fluidotherapy
- whirlpool
conversion
- heat transfer by conversion of non-thermal energy, such as mechanical , electrical or chemical energy, into heat. does not require direct contact of the agent and the patient
ex: US and diathermy
- heat transfer depends on the power of the energy source
examples of conversion
- US
- diathermy
radiation
- direct transfer of energy e/o need for contact or intervening medium. higher heat directed at lower heat area
- infared lamp, laser, UV light
evaporation
- energy absorption because of conversion of material from liquid to vapor
- vapocoolant spray
- spray and stretch technique
- sweating
cooling is used to:
- control inflammation, pain and edema
- reduce spasticity
- control symptoms of multiple sclerosis
- facilitate movement
cryotherapy Is most effective when
- in the acute stage of healing
- can be continued into the reconditioning stage
cryotherapy effects the body by influencing the following processes:
- hemodynamic
- neuromuscular
- metabolic processes
cryotherapy hemodynamic effects
-initial decrease in blood flow
- vasoconstriction
- <15-20 minutes duration
- repeating ice applicstion after an initial 20 minute application for two repetitions of 10 minutes off the 10 minutes on lowers blood flow more than a single 20 minute application
Hunting response
- when cold is applied longer or when tissue temperature is below 10 deg C cold induced vasodilation occurs
- indistal extremities exposed to cold more than 15 minutes there is a resultant in “hunting response”
- maintained vasodilation is seen in forearms at 1 deg C for 15 mintues
cryotherapy neuromuscular effects
- decreaseing nerve conduction velocity
- elevating the pain threshold
- altering muscle strength
- decreasing spasticity
- facilitating muscle contrcation
5 minutes cooling
- decreases nerve conduction velocity
- fully reverses within 15 minutes in normals
greater than 20 minutes of cooling
- reversal takes >30 minutes
- cold reduces conduction of both sensory and motor fibers. especially A-delta pain fibers
cryotherapy to decrease spasticity
- apply cold for up to 30 minutes on a hypertonic region
- effects can last 1-1.5 hours
- BRIEF ~5 minutes can cause decr in DTR
- 10-30 minutes decrease clonus
cryotherapy inflammation control
- less than 15 minutes for distal extremities
- up to 30 minutes for larger regions
- used in acute inflammatory phase
cryotherapy for pain control
- 10-15 minutes of cold, gives pain control for 1+ hours
- pain control due to: a-delta fiber blocking, gate control theory, reduced muscle spasm
cryokinetics
combines cold an exercise to treat pathology
- apply cold to the point of numbness to decr pain then allow exercise to regain ROM
- 20 minutes of cold then 3-5 minutes of exercise
cryostretch
- application of a cooling agent before stretching
- purpose: reduce muscle spasm allowing greater ROM increase
reasons for considering heat
- promotion of relaxation
- increased extensibility of collagen tissue and decr joint stiffness
- pain relief
- reduction of muscle spasm
- increase blood flow
- resolution of inflammatory infiltrates
- prepare stiff joints/tight muslces for exercise
heat effects tissue via:
- hemodynamic
- neuromuscular effects
- metabolic effects
- altered tissue extensibility
changes in muscle strength
- strength and endurance decreases during the initial 30 minutes after application of deep or superficial heating agents
- beyond 30 minutes and for up to 2 hours there is a gradual return in strength to rpior level, then an increase to above pretreatment strength levels
best practice for maximum increase of length is:
- tissue temp maintained at 41-45 deg C for 5-10 minutes
burns cell death temp
- cell dath above 45 deg C
