Unit 3 Lecture Flashcards
define ultrasound
- sound (not heard by humans) with a frequency greater than 20,000 Hz per second
what is ultrasound described by?
- intensity
- frequency
- duty cycle
what is a duty cycle?
the proportion of the total treatment time to the amount of time that the ultrasound is actually on
- 100% constantly on
- 50% 1:1
- 20% 1:4 (can be less than 20%)
how deep can the penetration of an ultrasound be on soft tissue?
up to 2-5 cm
describe a thermal ultrasound
continuous duty cycle
- increased tissue temp
- increased metabolic rate
- increased circulation
- increased soft tissue extensibility
- decreased pain
- decreased spasms
- altered NCV (nerve conduction velocity)
clinical application of thermal ultrasounds
decrease pain & increase soft tissue extensibility
describe a non-thermal ultrasound
pulsed duty cycle (20-50%)
- increased intracellular CA levels
- increased skin & cell membrane permeability
- increased macrophage permeability
- facilitates tissue healing
- modifies inflammation
- enhances transdermal drug delivery
- cavitation
- acoustic streaming
- microstreaming
which parameter of ultrasound determines whether it will be thermal or non-thermal?
duty cycle
cavitation
oscillation (movement back & forth) of gas bubbles that expand & contract because of changes in the sound field which leads to altered cellular function
acoustic streaming
- a steady & circular flow of cellular fluids in a sound field induced by ultrasound
- thought to alter cellular activity by transporting material from one part of the ultrasound field to the other
microstreaming
- these movements are small-magnitude movements & are known to alter cell membrane permeability & cellular activity
ERA
the area of the transducer that the energy of the ultrasound radiates from (it’s always smaller than the area of the treatment head)
BNR
Beam Nonuniformity Ration
- the ratio of the spatial peak intensity to the spatial average intensity (usually 5:1 or 6:1)
- the crystal expands & compresses material, then contracts & rarifies material
attenuation
- as sound travels through material, it slowly loses intensity (by absorption, reflection & refraction
- is greatest in tissues with high collagen content & with the use of high ultrasound frequencies
describe reflection, refraction, & absorption
- REFLECTION: occurs anytime sound travels from 1 medium to another & the medium densities are very different
- REFRACTION: occurs when the ultrasound beam is delivered at an angle; the angle that the wave enters the tissue with is different than the angle that the waves continues with through the tissue
- the wave becomes redirected (if the angle is too great, refraction can turn into reflection)
- ABSORPTION: transmission of the wave into the tissue (what we want to happen)
how is ultrasound different from other agents?
- reaches deeper tissues & heats smaller areas than other superficial thermal agents
describe high & low ultrasound absorption coefficients
- high: high collagen, low water content & heats more
- low: low collagen, high water content & heats less
what are the frequencies of an ultrasound & how is one chosen?
- 1 MHz or 3 MHz
- chosen based on how deep the area is or the type of structure being targeted
describe 1MHz
- lower frequency = deeper = HIGHER intensity
- 2-5cm deep
- intensity 1.5-2.5 W/cm2
- takes longer for temperature increase
describe 3 MHz
- higher frequency = superficial = LOWER intensity
- 1-2cm deep
- intensity 0.5-1.0 W/cm2
- maximum temperature increase is faster
what are factors that affect the amount of temperature increase?
- varies according to frequency, intensity, and duration
- rate is proportional to the absorption coefficient at the applied frequency
what are general clinical applications that would call for US?
- soft tissue heating
- pain control
- underwater US
- surgical incisions
- tendon & ligament injuries
- tendonitiis
- tendon healing post-op
- bone fractures
- phonophoresis
describe US use for soft tissue heating & the recommended parameters
continuous
- increases tissue temperature & extensibility
- increased tissue length is maintained better if force is applied while tissue temp is elevated & stretch is maintained for 5-10 minutes after US while tissue is cooling
- muscle: 3 minute window of staying warm
- tendon/ligament: 5 minute window of staying warm
recommended parameters
- 3MHz/ 0.5-1.0W/cm2/ 5-10min
- 1MHz/ 1.5-2.5W/cm2/ 5-10min
describe US use for pain control & the recommended parameters
continuous
- may control pain by altering pain transmission/perception or changes to the pain-causing condition
recommended parameters
- 1 or 3MHz/ 0.5-3W/cm2/ 3-10mins
describe use for an underwater US
- use when treatment area is smaller than the sound head or an irregular area
- make sure outlet has a GFI, sound head is 1 inch from body part, and the transducer is moving parallel to surface being treated
- DO NOT USE A METAL BASIN
not as good of a transmitter of US wave compared to gel
describe US use for surgical incisions & the recommended parameters
pulsed
- shown to facilitate angiogenesis
- found to reduce pain from surgical scars years after procedures
recommended parameters
3MHz/ 0.5-0.8W/cm2/ 3-5mins
describe US use for tendon & ligament injuries
pulsed
- assists in healing after surgical incisions & repair
- helpful in decreasing tendon inflammation
research findings are mixed
describe US use for tendonitis
parameter selection is very important
- acute - pulsed with low intensity
- chronic - continuous with high intensity (and stretching)
describe US use for bone fractures
pulsed
- use of low dose ultrasounds over healing fx sites is recommended to accelerate healing
describe US use for phonophoresis & the recommended parameters
pulsed
- application of US with a topical drug as the medium
- meds will be at a higher concentration & have a systemic effect
- DO NOT perform on a pt already taking the same type of medicine in a different form
recommended parameters
-3 MHz/ 0.5W/cm2/ 5mins
name commonly used drugs with phonophoresis
- NSAIDS - ketoprofen gel
- corticosteroids - dexemthasone
- anti-inflammatory
- biofreeze
name the adverse effects of ultrasound & how to prevent them
- BURNS: check sensation & mentation before treatment, keep the sounded head moving, and use the correct intensity
- BLOOD CELL STATIS: use the correct speed while keeping the head moving
- CROSS-CONTAMINATION: clean the transducer head & head of gel bottle with alcohol before & after use
contraindications for ultrasound (PPP, JTEC, RM)
- pacemaker
- plastic components
- pregnancy
- joint cement
- thrombophlebitis
- eyes
- CNS tissue
- reproductive organs
- malignant tumor
precautions for ultrasound (FABE)
- fractures
- acute inflammation
- breast implants
- epiphyseal plates
define electrical current
the flow of charged particles through a conductor
define charge
the amount of unbalanced electricity in the body
define polarity
positive or negative
define anode & cathode
anode: the positive electrode
cathode: the negative electrode
define resistance
opposition of a material to the flow of the electrical current
define impedance
resistance to an alternating current
what are the 3 effects of e-stim?
- nerve depolarization
- muscle depolarization
- ionic effects
describe nerve depolarization
- electrical currents depolarize nerve membranes & produce action potentials
- action potential is propagated along the axon until it reaches its terminus
- the body will respond to this the same way it responds to action potentials that are caused by physiological stimuli
describe resting membrane potential
at rest, the inside of a nerve is -60 to -90Mv compared to outside
describe the absolute refractory period
when the nerve is depolarized, no more action potentials can be generated
describe the relative refractory period
after depolarization (before returning to the resting membrane potential) there is a brief period of membrane hyperpolarization
a stronger stimulus than normal is needed for an action potential
describe the strength duration curve
the minimum amount of strength (amplitude) & pulse duration needed to depolarize the nerve
what is the predictable order of the strength duration curve?
- sensory: low amplitude & short pulse durations (less than 80)
- motor: higher amplitude & longer pulse durations (150-350)
- noxious: even higher amplitude & even longer pulse durations
describe muscle depolarization
- INNERVATED MUSCLE
- will respond by muscle contraction to short pulses
- the current causes depolarization of their motor nerves (Neuromuscular Electrical Stimulation (NES))
- DENERVATED MUSCLE
- will only contract in response to pulses of electricity lasting 10ms or longer & require a special stimulator
- the longer duration of pulses of electricity depolarize the muscle cell directly (Electrical Muscle Stimulation (EMS))
describe ionic effects of e-stim
can occur in tissue when a net charge is left in the tissue
describe direct current
- monophasic
- flows in ONE direction into the tissue
- has 1 phase & 1 polarity (+ or -)
- USE FOR: iontophoresis, stimulation of denervated mm, & wound healing
describe alternating current
- biphasic
- a continuous uninterrupted flow of charged particles (+ and -)
what it puts into the tissue, it pulls out - 3 types: IFC, Premodulated, Russian
describe IFC
- alternating current
- 2 channels, 4 electrodes
- an intersecting medium frequency current
- Beat frequency created by the difference of frequencies of the channels
- used for bigger areas
- USE FOR: pain control
describe premodulated current
- alternating current
- 1 channel, 2 electrodes
- medium frequency
- same wave from as IFC
- e-stim produces Beat
- used for smaller areas
- USE FOR: pain control
describe russian current
- alternating current
- medium frequency of 2500MHz
- delivered in 50 bursts per second
- each burst is 10ms long & is separated from the next burst by a 10ms interburst interval
- 10 seconds on, 50 seconds off for 20-30 minutes
- used for larger muscle groups
- USE FOR: strengthening
describe pulsed current
- interrupted flow of charged particles
- may be balanced or unbalanced
- may flow in 1 or both directions
- may be symmetrical or asymmetrical
- 4 types: biphasic, balanced symmetrical/asymmetrical, unbalanced asymmetrical, monophasic (HVPC)
describe biphasic pulsed current
charged particles move in one direction & then in the oppsote direction
describe a balanced asymmetrical current
the charges of the phases are EQUAL in AMOUNT and OPPOSITE in POLARITY resulting in a net charge of 0
describe an unbalanced asymmetrical current
the charges of the phases are not equal & there is a net charge left in the body
describe a monophasic current (HVPC)
charged particles move only in ONE direction or flow back & forth during each pulse
biphasic pulsed current uses
pain control & muscle strengthening
HPVC uses
tissue healing & edema management
define frequency
the number of pulses per second
define pulse duration
the time from the beginning of the first phase to the last phase of a pulse
define phase duration
the duration of 1 phase within a pulse
define interpulse interval
time between pulses
define interphase interval
time between phases of a pulse
define ramp up time
the time it takes for the current amplitude to increase from 0 to its maximum amplitude
define ramp down time
the time it takes for the current amplitude to decrease from its maximum amplitude to 0
define modulation
any pattern of variation in one or more of the stimulation parameters
define amplitude
the magnitude of current or voltage
describe the differences in a physiological and e-stim produced contraction
- (P) type l fibers (ST: Slow Twitch) are activated first (more fatigue & atrophy resistant)
- (E) type ll fibers (FT: Fast Twitch) are activated first because of the recruitment of the nerve fibers with the largest diameter axons (fatigue & atrophy quickly)
- (P) contraction is gradual & smooth
- (E) contraction has a rapid onset
- (P) asynchronous firing
- (E) synchronous firing
