Lecture 2: Thermal Agents Flashcards
What are thermal agents
transfer energy to increase/decrease tissue temp
examples of thermotherapy
icepack
hot pack
US
whirlpool
diathermy
modes of heat transfer
conduction
convection
conversion
radiation
evaporation
what is conduction
energy exchange by direct contact of stationary materials at different temp
heat goes from material at a higher temp to material at a lower temp
factors that affect heat transfer
tissue thickness (inverse relationship)
area of contact
thermal conductivity
temp difference
rules for conduction
greater temp difference = faster rate of heat transfer
make sure conductive agents are not significantly different from pts skin temp to avoid burns
use materials that can create a safe medium for heat transfer
ex of materials that have high/low thermal conductivity
high = metal
low = towels
how many layers of towels are recommended for heat transfer
6-8 towels
what is convection
direct contact vetween circulating medium and other material of a diff. temp
faster transfer with faster movement
ex = whirplool and fluid therapy and hyperice X
what is conversion
converting a non thermal form of energy to heat
i.e. mechanical, chemical, or electrical
doesnt require direct contact
DOES require intervening material to help transmit the certain type of energy (i.e. US gel)
rate of transfer depends on power source
examples of conversions
US (mechanical energy) = absorbs sound waves
diathermy (electromagnetic) = rotation of polar molecules; friction between molecules increases temp
what do we need to know about specific heat
greater = more energy required for increase of temp to occur
i.e. water has a higher specific hear than air
tissues with high specific heat may require more time with thermal agents (fat has lower specific heat than muscle)
main effects of cryotherapy
hemodynamic (vasoconstrict)
neuromuscular (reduce pain)
metabolic (lower inflammation)
how long does it take for vasoconstriction to occur
10-15 min to reduce blood flow
most pronounced in area of direct skin contact
what is the cold induced vasodilation phenomenon
following initial decrease of blood flow there is a later increase on blood flow which cycles up and down
occurs when cold is applied for more than 15 min or when tissue becomes less than 50 deg
how does pain reduction occur with cryotherapy
decrease nerve conduction velocity of sensory and motor nerves (myelinated nociceptive- A delta)
increased pain threshold by stimulation of cold receptors (blocks peripheral pain stimuli)
describe how muscles are affected by cryotherapy
decreased spasticity (effects last 1-1.5 hours due to decrease in gamma motorneruon activity)
increase muscle strength by facilitating muscle contraction (isometric increases in less than 5 min, 30 min of cryo causes an initial decrease in isometric strength then increase in strength an hour later that is sustained for 3 hours)
what are the metabolic reactions to cryotherapy
cold decreases the rate of all metabolic rxns
decrease in rate of inflammation by decreasing the activity of cartilage degrading enzymes and level of histamines
decrease in inflammatory process die to joint disease such as OA or RA
what does cryotherapy do during the acute phase of healing
control bleeding, edema, and pain due to inflammation
how does cryo directly decerase the heat and edema associated with inflammation
by decreasing blood flow
other inflammatory benefits of cryotherapy
acute flare ups for chronic inflammatory diseases
reduced severity of DOMS
how does cryotherpay help edema
reduced release of histamines (which increase vascular permeability)
increases blood viscosity and devreases blood flow
fluid doesnt build up
what is cryokinetics
apply ice after injury ASAP
allows pain free ex during numbness for 3-5 min
repeat 5x
used in athletics to minimize loss of play time
what is cryostretch
capocoolant spray used as coolign agents
followed up with stretch to decrease muscle spasm and increase ROM
what can thermotherapy do
control pain
increase soft tissue extensibility and circulation
accelerate healing
hemodynamic, neuromuscular, metabolic effects asa well as altered tissue extensibility
of the uses of physical agents, which are specific to heat
accelerate healing
pain management
collagen extensibility
physiological considerations of thermotherapy
the deeper the tissue, the less heat energy
to heat deep muscles, use exercise or deep heating modalities such as US or diathermy
hemodynamic effects of thermotherapy (heat)
increase blood flow
increase permeability (can increase edema)
what are the neuromuscular effects of thermotherapy
increase n conduction
changes frequency of nerve firing rate (decreased firing of muscle spindle) = relax muscle, decrease spasm, decrease resistance to passive stretch
muscular effects of thermotherapy
muscle endurance and strength decreases during forst 30 min
muscle strength gradually recovers for the next 2 hours above pre treatment levels
metabolic effects of thermotherapy
increase rate of cellular biochemical rxns (increased metabolic activity)
increased o2 uptake (accelerate healing bc more o2 available for tissue repair)
BUT also increased metabolic rate of destructive processes (avoid areas of inflammation or pts with acute/chronic inflammatory diseases like OA or RA)
what happens when collagen tissue is stretched without prior heating
elastic deformation
what happens when tissue is heated before stretched
increase in stretch
greater increase in length with stretch occurs
less force required to achieve increased length
decrease risk of tissue tear
what are superificial heating agents good for when stretching
cutaneous scar tissue or superficial tendonds
what are deep heating agents good for when stretching
large deep muscles or deep tendons
how does heat control pain
cutaneous thermoreceptors “gate” pain
nociceptor signals blocked by thermoreceptors
body feels temp instead of pain
** not to use in inflammatory stage
how does heat increase joint ROM
increased soft tissue extensibility
max increase in length with low risk to injury 5-10 min of low load prolonged stretch while heating
how does heat decrease joint stiffness
due to increased extensibility and vsicoelasticity of joint capsule and surrounding ligaments
via warm water, paraffin bath, or infared lamp
how does heat accelerate healing
increased circulation and enzymatic activity
accelerates blood delivery to tissues
brings oxygen/nutrients
increases amount of o2 via dissociation from hemoglobin
best during proliferative or remodeling stage
how does heat cause superficial muscle relaxation
change frequency of n firing
decreased firing of alpha motor neurons
decrease spasm
good for LBP/spasm
contraindications for heat
acute inflammatory/MSK conditions
impaired sensations
malignant tumors
impaired cognition
thrombophlebitis (DVT)
acute trauma
recent/potential hemorrhage
precautions for heat
pregnancy (avoid abdomen/low back)
poor circulation
edema
cardiac insufficiency
areas with metal (staples/jewelry)
over open wound
areas where topical counterirritants have been applied
demyelinated nerves
adverse effects of heat
burns (superficial agents safer; make sure don’t fall asleep)
fainting (vasodilation = decreased blood flow to brain; orthostatic effects post treatment)
bleeding (may aggravate in areas of acute trauma/hemophilia)
always give pt way to stop treatment
PT considerations for heat
errors in rehab techniques can lead to adverse outcomes like burns
32% of burn legal claims are from hot packs
