Physical Agents Midterm Review Flashcards
What do physical agents do?
Modify tissue inflammation and healing
Relieve pain
Alter collagen extensibility
Modify muscle tone/contracting ability
deep heating thermal agents
ultrasound and diathermy
superficial heating thermal agents
hot pack and paraffin
superficial cooling agents
cold pack, ice massage
mechanical agents
mechanical traction
compression (bandage, stockings)
water (whirlpool)
sound (ultrasound)
electromagnetic fields
ultraviolet, laser
electrical currents
TENS/IFC NMES/Russian High Volt Iontophoresis EMG
steps in choosing a modality
goals and effects of treatment
contraindications and precautions
evidence for physical agent use
cost, convenience and availability
characteristics of A-delta fibers
respond to intense mechanical stimulation and heat or cold
–short duration, sharp, stabbing, or pricking sensation
–small and myelinated
–4-30 m/s
–20% of pain afferents
–not blocked by opioids
characteristics of C afferent fibers
longer duration, dull, throbbing, aching, burning, tingling, diffusely localized, accompanied by sweating, increased heart rate and blood pressure, and nausea –small and unmyelinated –0.5-2 m/s –80% of pain afferents –can be blocked by opioid medication
characteristics of A- beta
non-painful sensation related to vibration, stretching, and mechanical pressure
carries epicritic information
What is the neuromatrix pain theory?
Pain is a multidimensional experience produced by “neurosignature” patterns of nerve impulses
Neural network distributed throughout many areas of brain
Neuromatrix genetically determined, modified by sensory inputs
Neurosignature’s output pattern determined by multiple influences (not only somatic sensory)
How long is the duration of pain relief for endogenous opioid system?
4-6 hours
how long is the duration of pain relief for gate control?
as long as the stimulus is applied
physiological effects of heat
Vasodilation
Increase metabolism
For every 10ºC rise in temp, there is 2-3x higher rate of metabolism
Pain relief
Decrease stiffness
Enhance extensibility
Requires elevation of tissue temp to 40-45ºC
Reduce muscle spasms/decreased strength
First 30 minutes after application of heat; returns to pre-tx levels after 2 hours
What is the peak temp time for heat?
within 6-8 minutes it can penetrate about 0.5 cm
What is the longer duration for penetrating 1-2 cm?
about 15-30 minutes
What is the rise in temp for 3 cm?
about 1 degrees celsius
Through what mechanism do hot packs work?
conduction
how many layers of towels do you need for a hot pack?
6-10 layers
When do you reach max results?
after 20 minues
When should you check on the patient with heat?
after 5-6 minutes
What should heat feel like?
warm towels fresh out of the dryer
How does paraffin work?
conduction
mineral oil that alters the melting point and lowers specific heart to make higher temps more tolerable
126-130 degrees
What mechanism does cold use?
conduction. convection and evaporation
what is the ideal tissue temp for cold treatment?
15-25 degrees celcisus
55-77 degreesF
What is the order of sensation for application of cold?
- cold
- warm, burning
- achy, tingling
- numbness
How long should cold pack be applied?
15- 30 minutes
When is cold most effective?
5-10 minutes after an injury and can still be helpful up to 72 hours after injury
physiological effects of cold
Vasoconstriction
Decrease metabolism
Pain relief (decrease nerve conduction velocity)
Augment muscle contraction
What level do you need to reach for ice?
to go beyond numbness
Mechanism of ultrasound
reverse piezoelectric effect
what is the reverse piezoelectric effect?
Electrical current (AC current) applied to lead zirconate titanate crystal in sound head which is converted to mechanical energy
Relationship of frequency, absorption and penetration
the higher the frequency, the higher the absorption BUT less depth of penetration
What ratio is better for the beam of the ultrasound
a lower beam non-uniformity ratio (BNR) is better
If BNR = 5:1 and intensity is 0.5 W/cm2 what is the spatial peak intensity?
- 5 W/cm2
0. 5 * 5= 2.5
What is attenuation?
the decrease in energy due to absorption, reflection and refraction
it is inversely related to penetration
how much does absorption account for attenuation?
absorption accounts for half of attenuation
Tissues with higher attenuation show a…
BIGGER temperature rise
Tissues with higher collagen content have….
HIGHER attenuation
as the frequency of US increases,what happens to attenuation?
attenuation INCREASES
What is the type of tissue with the highest attenuation?
BONE
because it is collagen rich
What type of tissue has the lowest attenuation?
nerves with 0 attenuation
blood fat and muscle are also the lowestq
What are the effects is the duty cycle is 100%
both thermal and mechanical
What is the duty cycle for mechanical only?
20%