Therapeutic application results in a transfer of heat to/from
- pt body
- btw tissues and fluids of body
heating agents transfer heat to
cooling agents transfer heat
away from body
what are local physiological reaction to thermal modalities
- localized sweating
- Changes in local metabolic rate, blood flow and skin conditions
What are Systemic physiological reaction to thermal modalities
- generalized sweating or shivering
- cardiovascular changes
thermal agents include?
- cryotherapy/ gel packs
- superficial heat
- deep heat
examples of superficial heat
- moist heat packs
- paraffin-wax bath
examples of deep heat
Deep heat is also considered what?
superficial thermal agents change temperature of what?
- superficial subcutaneous tissues
Heat that, when applied at a maximally safe clinical dosage, is only capable to raising the temperature of the skin and superficial tissues (up to 2 cm deep) to a thermally significant level.
superficial heat is dry or moist ?
deep heating agents increase temperature of deeper tissues like
- large muscles
- periarticular structures
deep heating agents heat up to depth of
deep heat is in the form of
electromagnetic or magnetic energy
deep heat in the form of electromagnetic or magnetic energy is transmitted through
the skin and absorbed in deeper tissues (up to 5 cm) where it increases the kinetic action of molecules
what are the modes of heat transfer? (5)
materials with higher specific heat?
- skin > fat or bone
- water > air
materials with a high specific heat requires more
energy to achieve the same temp increase than materials with low SH
Materials with high specific heat hold
more energy than materials with low SH at same temp
thermal agents with high SH are applied at what to transfer the same amount of heat
what is conduction
an energy exchange by direct collision btw the molecules of two materials at diff temps
conduction requires what type of contact of the targeted area with the heating or cooling agent
heat transfer by conduction occurs only btw materials of
different temps that are in direct contact with each other
safe and effective rate of heat transfer requires?
- Choosing materials with moderate thermal conductivity
- ensuring tolerable diff in temp
- using insulators to limit rate of heat transfer
guidelines for heat transfer by conduction are?
- the greater the temp diff btw heating/cooling agent and the body part it is applied to, faster the rate of heat transfer
- materials with high thermal conductivity transfer heat faster than materials with low conductivity
- the larger the area of contact btw a thermal agent and pt, the great the total heat transfer
- rate of temp rise decrease in proportion to thickness
how many layers of toweling should be used btw hot pack and pt to avoid burns
what should you remove before using conductive thermal agent?
what is convection
heat transfer by direct contact between a circulating medium with another material of a different temp
convection transfer more heat than
conduction in the same time period
examples of convection
circulating blood helps maintain physiologic temperature by
non-thermal form of energy into heat
conversion can be what type of energy
mechanical, electrical or chemical
ultrasound causes mechanical
vibration of molecules
diathermy applies electromagnetic energy to the body, causing
rotation of polar molecules
some cold packs require
chemical reaction to turn cold
the temperature of thermal agent is not important, what is?
the power of the energy source is important
conversion does not require
conversion does require?
intervening material to be a good transmitter for that type of energy
conversion rate of tissue temp increases depends on what 4 things?
- size of treatment area
- size of applicator
- efficiency of transmission from applicator to pt
- type of tissue being treated
what is radiation?
a direct transfer of energy from material of higher temp to material with lower temp without the need for an intervening medium or contact
what transfer heat by irradiation?
radiation rate of temp change depends on
- intensity of radiation
- relative sizes of the radiation source and treatment area
- distance and angle of the radiation to the treatment area
During evaporation energy is absorbed to change what
liquid into a gas or vapor
what is cooled in the process of evaporation
the material that contributes energy for evaporating
examples of evaporation
vapocoolant spray or when sweat evaporates
what impairs evaporation
what responds to temp increase
metabolic, vascular, systemic
metabolic response to temp increase is
an increase in metabolic rate
vascular response to temp increase is
systemic response to temp increase is
cardiovascular, sudomotor, respiratory, and renal
An increase in metabolic rate causes what 2 things?
- increase in phagocytosis
- Arteriolar dilation
and increase in phagocytosis may to what?
hasten healing process
restoration of damaged tissues
Arteriolar dilation increases
blow flow at heated site
precautions of metabolic responses
vascular, renal, sweat balance mechanisms
Pros of vasodilation
- increase in rate of clearing metabolites (decreases pain or muscle spasms caused by the accumulation of lactic acid or other waste products)
- Increase in amount of cooler blood arriving at the area and warmer blood being carried away, (helps prevent tissue damage from excessive heating)
Con of vasodilation
increase in bleeding at injured tissue site or hemorrhage in its with ulcers and hemophilia
- drop in peripheral blood pressure
- increase heart rate
generalized vasodilation may create a drop in what
peripheral blood pressure
therapeutic effects of system responses increase in blood flow which does what
brings nutrients to area
precautions for systemic responses
- increased bleeding
- drop in BP–> fainting
sweat prevents what?
an increase in body temp
how does sweat prevent an increase in body temp
process of evaporation, reducing local body temperature
Sweating results from activation of what
sweat glans when skin temp rises above 91.4
respiratory responses increase breathing rate to do what
rid body of heat through evaporation of moisture in exhaled air
how much of evaporation is loss through reparatory tract?
renal responses rid the body of what
increase in metabolic by-products
what is lost during urination
some heat (minimal/ insignificant )
skin and fat are?
Vascular problems will prevent what
normal protective mechanisms to prevent tissue damage
the ability of modality to give heat to the body depends on what?
- amount of heat modality can provide
- thermal conductivity properties
- temp gradient btw pt and modality and time of application
what is a definite contraindication to thermal therapy
severely impaired skin discrimination
how many level of skin should be tested for sensory heat and cold discrimination ?