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)
is it appropriate to ice an injury during the proliferative stage?
no, icing weeks later after an injury can be harmful to the healing process
cryotherapy during the acute inflammatory phase of healing helps to control what 3 things?
bleeding (vasoconstriction)
edema (vasoconstriction + decreased metabolic activity)
pain (neuromuscular effects of pain reduction and secondary pain effects of edema)
how does cryotherapy help inflammatory diseases such as OA and RA?
reduces inflammation/pain associated with flare ups
how does cryotherapy help post exercise?
reduces the severity of delayed onset muscle soreness (DOMS), eccentric exercises, and high intensity exercises
what is edema?
presence of abnormal amount of fluid in the extracellular tissue spaces of the body
what is the acute inflammation formation process?
trauma + increased intravascular fluid pressure and vascular permeability push fluid into the interstitial (fluid-filled space between skin or cell membranes)
how does cryotherapy control acute edema?
reduces the release of histamines (as histamines increase capillary permeability)
increases blood viscosity
decrease blood flow (vasoconstriction)
how do we minimize edema?
apply ice ASAP post injury and combine with compression and elevation (RICE) to drive extravascular fluid into venous and lymphatic drainage systems
is cryotherapy appropriate to control edema caused by immobility and poor circulation?
no
true or false: applying cryotherapy for 10-15 minutes can control pain for 1 or more hours after treatment
true
what are the neuro physiological effects of cryotherapy that control pain?
gates pain transmission by blocking cutaneous nociceptors (P! receptors) + by decreasing nerve velocity of A-delta fibers (P! pathways)
what is thermotherapy?
therapeutic use of heat in rehab medicine
what are the 3 main goals of thermotherapy?
control pain
increase soft tissue extensibility + circulation
accelerate healing
what are some types/application techniques of thermotherapy?
hot pack
paraffin wax
ultrasound
diathermy
fluidotherapy
infrared lamps
hydrotherapy (whirlpool)
contrast bath (whirlpool)
aquatic therapy (warm water)
what hemodynamic effect does thermotherapy physiologically have on the body?
vasodilation (and increased capillary permeability)
what neuromuscular effect does thermotherapy physiologically have on the body?
pain gating
what metabolic effect does thermotherapy physiologically have on the body?
increased metabolic rate
true or false: superficial tissue that has direct contact with the energy source experiences faster temperature changes than subcutaneous tissues that do not have direct contact
true (muscles and joints show low temperature changes (if any) depending on size, structure, depth, and specific heat)
what form of thermotherapy would be appropriate to use when wanting to heat deep muscles and why?
ultrasound, diathermy, or exercise
(superficial heating agents do not heat to the depth of most muscles)
how does thermotherapy affect nerve conduction velocity between motor and sensory nerves?
increases velocity
how does thermotherapy change the frequency of nerve during rates?
heat relaxes the muscles during stretch and spasm, which results in decreased firing rates of the muscle spindles and decreases the resistance to passive stretch
how does thermotherapy increase pain threshold/reduce pain?
pain gating + stimulation of cutaneous thermoreceptors that block nociceptor/pain signals from getting back to the brain = body feels change in temperature instead of pain
true or false: muscle strength and endurance decrease during the initial 30 minutes following heat agents
true
true or false: heat is used for muscle strengthening
false, the strength that comes from heating is only temporary (2 hours)
what are the metabolic effects of thermotherapy?
increases rate of cellular biomechanical reactions (increases metabolic rate) +
increased oxygen uptake to accelerate healing (more oxygen for tissue repair)
what is the downgrade of thermotherapy increasing metabolic rate?
it also increases the metabolic rate of destructive processes
therefore, avoid in areas of inflammation or patients with acute or chronic inflammatory disease OA and RA + patients with metastases or blood clots (possible embolism and stroke)
true or false: increasing the temperature of soft tissue increases its extensibility
ture
what is extensibility?
the amount of stretch/deformation that can occur
what is plastic deformation?
tissue maintains increased length during stretching
what is elastic deformation of tissue?
occurs when the collagenous tissue is stretched without prior heating
what are some things that occur when soft tissue is heated before stretching?
increased strength
achieves a greater increase in length when the stretching force is applied
less force is required to achieve this increased length
decreased risk of tearing tissue
what types of tissues are superficial heating agents (example: hot pack) used for?
cutaneous scar tissue or superficial tendons
what types of tissues are deep heating agents (example: ultrasound) used for?
large deep muscles or deeper tendons
what are some clinical uses of superficial heat?
pain control
increase ROM
decrease joint stiffness
accelerated healing (increased circulation and enzyme activity)
infrared radiation for psoriasis or deal ulcers (integumentary)
superficial muscle relaxation
true or false: thermotherapy/heating is recommended for pain caused by acute inflammation
false (this would cause more swelling and more pain)
true or false: research shows 8 hours of continuous, low-level heat has been shown to decrease pain associated with DOMS and back pain
true
how does thermotherpay increase the ROM in joints?
due to increased soft tissue extensibility that occurs with increased tissue temperature
heat therapy enables greater increases in soft tissue length, while decreases the likelihood of injury when a passive stretch is applied
how does thermotherpay decrease joint stiffness?
due to increased extensibility and viscoelasticity of joint capsule and surrounding ligaments
how can thermotherapy accelerate tissue healing?
by increasing the circulation and the enzymatic activity rate
true or false: the best treatment time for thermotherapy is during the proliferative or remodeling stage of healing or when chronic inflammation is present
true
why is it not appropriate to apply het during the acute inflammatory phase?
heat can prolong this phase due to increase in edema and delay healing
what are some clinical contraindications of thermotherapy?
acute trauma
acute MSK + inflammatory conditions
recent or potential hemorrhage
thrombophlebitis (DVT)
impaired sensation
impaired cognition
malignancy tumors (acute stage)
what are some clinical precautions of thermotherapy?
pregnancy (avoid abdomen and low back)
poor circulation or thermal regulation
edema
cardiac insufficiency
areas with metal (jewelry, staples)
over an open wound
areas where topical counterirritants have recently been applied (capsaicin)
demyelinated nerves
what are some adverse effects of thermotherapy?
burns
fainting
bleeding
how can thermotherapy possibly cause fainting?
vasodilation in other parts of the body lead to decreased blood flow to the brain + orthostatic effects following thermotherapy treatment (so have patient’s head elevated during treatment and wait a few minutes following treatment before rising)
how can thermotherapy possibly cause burns?
excessive heat can cause cell death
how can thermotherapy possibly cause bleeding?
heat may aggravate bleeding in areas of acute trauma or hemophilia or could possibly re-open a current lesion
what are some PT considerations when considering the downsides to the use of hot packs?
errors in rehab techniques (application) can lead to adverse outcomes such as burns or allegations
