Thermal Agents Flashcards
what are thermal agents?
agents that transfer energy to a patient to increase or decrease tissue temperature
what are some examples of thermal agents?
ice packs
hot packs
ultrasound
whirlpool
diathermy
what are the 5 modes of heat transfer?
conduction
convection
conversion
radiation
evaporation
what is conduction?
energy exchange by direct contact of stationary materials (tissues) at different temperatures
true or false: heat is conducted from the material at a lower temp to the material at a lower temp
false HIGHER TO LOWER TEMP!!
what is the direction of heat transfer with hot pack and patient’s skin?
heat is transferred from hot pack to skin
what is the direction of heat transfer with cold pack and patient’s skin?
heat is transferred from skin to cold pack
what is thermal conductivity?
rate at which a material transfers heat by conduction (NOT the same as specific heat)
why is there a safety concern with faster rates of heat transfer?
can cause P! or burn the skin
how do you avoid burns?
by treating with conductive agents that have temperatures that are not significantly different that the patient’s skin temperature (washing burns with room temperature water instead of cold)
+ use materials that create a safe medium for heat transfer and remove all metal jewelry from areas of contact (metal has a high thermal conductivity)
what is convection?
direct contact between circulating medium (opposed to stationary) and another material of a different temperature (think vector = movement with direction)
true or false: heat transfer occurs more rapidly based on faster speed of movement between two materials
true (whirlpool is an example)
what is conversion?
converting a non-thermal form of energy into heat (mechanical, electrical, or chemical energy)
does conversion require direct contact?
no it requires an intervening material to help transmit the certain type of energy (ultrasound gel)
true or false: rate of transfer depends on the power of the energy source not the temperature
true (example: ultrasound gel does not need to be hot)
what is a mechanical form of energy that can be “converted” to heat when a sufficient intensity to a tissue absorbs the sound waves?
ultrasound
what is an electromagnetic form of energy which causes the rotation of polar molecules and “converts” to heat when friction between the molecules increases tissue temperature?
diathermy
what is specific heat?
amount of energy required to increase the temperature of a material by a “x” number of degrees (in celsius)
true or false: materials and tissues with low specific heat require more energy to heat and hold more energy compared to materials with high specific heat
false (tissues with HIGH specific heat require more energy to heat + hold more energy compared to LOW specific heat)
what are some examples of structures that have higher specific heat values?
water
skin
muscle
what are some examples of structures that have lower specific heat values?
air
fat
bone
what is cryotherapy?
therapeutic use of cold in rehab medicine
what is abstraction?
the removal of heat by means of conduction or evaporation
what are the 3 main categories of physiological effects in modalities?
hemodynamic
neuromuscular effect
metabolic effect
what hemodynamic effect does cryotherapy physiologically have on the body?
vasoconstriction
what neuromuscular effect does cryotherapy physiologically have on the body?
pain reduction
what metabolic effect does cryotherapy physiologically have on the body?
decreases inflammatory activity
what is the cold-induced vasodilation phenomenon?
an initial decrease in blood flow is followed by a later increase in blood flow that occurs when cold is applied for longer than 15 minutes or when tissue temperature reaches less than 50 degrees (happens primarily in fingers and toes)
EFFECTS TREATMENT TIME because it is the opposite of this healing stage’s goal
how does cryotherapy reduce pain?
(neuromuscular effect)
decreases the conduction velocity of the nerves that send pain signals to the brain (myelinated, nociceptive (pain) fibers A-delta) + increases pain threshold by stimulating cold receptors (blocks perception of painful stimuli: P! gating)
what are two other neuromuscular effects that cryotherapy has on the body?
decreases muscle spasticity (by decreasing gamma motoneuron activity)
increases muscle strength (by facilitating muscle contraction)
does cryotherapy increase or decrease metabolic reactions? example: inflammation
decrease
by decreasing the activity of cartilage degrading enzymes and the level of histamines + by decreasing inflammatory processes due to joint diseases such as osteoarthritis and rheumatoid arthritis)