low frequency currents Flashcards
Gliedmaster classification of currents?
Low frequency-1,000hz: irritating/stimulating
Medium frequency- 10,000hz: deeper effect w/ reduced skin irritation due to lower skin resistance
High frequency- 100,000hz; analgesia
ypes of currents according to phases
Monophasic
monophasic, diphasic, pulsatile
describe a Monophasic current
Unidirectional and uninterrupted
From positive to negative electrodes
E.g. galvanic current
describe a galvanic current
constant flow and intensity
Constant voltage
Direct current= unidirectional flow of electrons
Diphasic
Diphasic
Alternating and bidirectional current flow
Reversible polarity
pulsatile
Can be mono or bi-phasic
Magnitude and intensity subject to change
Low frequency currents
list the Low frequency currents
galvanic and low frequency pulse currents
describe a galvanic current
- Unidirectional flow 2. Direct current 3. Constant voltage unchanged with time
describe low frequency pulse current
pulses and pauses. Each pulse has the same intensity but different shapes
how to generate a galvanic current
Apply an electric charge to stimulate molecues to become charged ions
NAOH migrates to the cathode and HCL migrates to the anode
Hydrophilic pads to protect skin from the burning/ irritative sensation at the cathode
Analgesic effect occ
Generall adults=0.02m amps/cm2 Children 0.1 m aurs at the positive anode
The dose is subjective to when the patient describes pins and needles due to the increased intensity. mps per cm2
Galvanic strucutres stimulate excitable structures e.g.
Eyes= light phenomena
Skin= sensation
muslces= contraction
what are the 3 zones in the skin
- polar zone
- peripolar zone
- interpolar zone
what happens in the polar zone:
DC causes charged particles to migrate
The particles have altered chem characteristics
Electro Neutralization of the opposite charged particles occurs
No therapeutic effect as they’re electrically inactive
Hcl is synthesised at the anode- site of sensation and irritation. Hydrophilic pads used to prevent skin burning
Naoh is synthesized at the cathode-site of analgesia
what happens in the peripolar zone:
The specific effects of the low frequency currents are exhibited
Tissue excitability is altered(improved)
For analgesia the anode is placed on the site of pain
what happens in the interperolar zone
on specific reactions e.g. Circulation metabolism Trophics-(relating to, or characterized by (such) nutrition) improving skin due to stimulating blood flow Substance exchange
what is iontophoresis
technique of introducing ionic medicinal compounds into the body through the skin by applying a local electric current.
how are galvanic curretns used for iontophoresis
Static galvanic current used
Drug activity enhanced by increasing low current intensity
lidocain= analgesia is increased
nivalin(galantamine)= improves neuromuscular transmission in the peripheral nerves
Anode exaggerates drug effects so placed at topical drug site.
Cathode neutralizes them due to increased irritation(keep away from the cathode)
methods to apply low frequency currents
Local- hydrophilic pads on body: Transverse pads, diagonal pads, longitudinal pads
Current bath
Reflex: Galvanic collar, Galvanic pants
galvanic current indications
Pain
Trauma
Paravertebral spams(disc hernia)
Osteoarthritis 4Circulation disorders
galvanic currents conraindications
- pregnancy 2. Myasthenia gravis
- Acute cardiac conditions
- Fever and inflammation
describe low frequency pulse currents
For smooth and skeletal muscle stimulation
Defined as low frequency currents up to 1000hz
what are the 6 physical parameters of low frequency pulse currents
- pulse shape
- pulse duration in ms
- pause duration in ms
- frequency
- period
- intensitiy in milliamps
explain pulse shape parameter of low frequency currents
Shows the ability of the muscle to accommodate
Healthy muscles-short duration intense stimulation shows rectangle shape
Peripheral nerve damage = triangle. -> higher intensity and duration needed
With exponential / forefront wave shows lack of accommodation requires increased stim and longer duration
pulse shape of healthy muscles
short duration intense stimulation shows rectangle shape
pulse shape of PND
angle. -> higher intensity and duration needed
what is an exponential / forefrint wave shape show
ack of accommodation requires increased stim and longer duration
explain pulse duration
hronaxie= min time required for muscular contractions to occur if 2 rheobases are used. Used to measure the duration of the pulse which shows the conditions of the muscles
rheobase= min intensity to overcome threshold. In this case it’s overcoming the threshold to simulate the muscle
Normal chronaxie= 1-2 ms
Pain chronaxie= 0.5-100ms
Peripheral paralysis chronaxie=100-200ms
what is chronaxie
in time required for muscular contractions to occur if 2 rheobases are used.
Used to measure the duration of the pulse which shows the conditions of the muscles
what is rheobase
heobase= min intensity to overcome threshold. In this case it’s overcoming the threshold to simulate the muscle
what is the normal chronaxie
1-2 ms
pain chronaxie
0.5-100ms
Peripheral paralysis chronaxie
100-200ms
what is the Pause duration in ms-1 for
Responds to the refractory period-no contraction even if stimuli is applied
Pauses is needed for muscle recovery=more severe damage requires longer pause on graph
what does the Frequency in the LFPWC
In hz
Shows functional mobility of muscle5.
1000ms-1/T = hz?
what is the period in LFPWC
T=t(i) -time of pulse + t(p) time pf pause. A period 3-6 times larger shows PND
what are the LFPWC parameters in a healthy muscle
t(i) =1-2ms
t(p)+t(i)=T eu
f= 50/100hz
what are the LFPWC parameters in a PND
t(i) 50/100/200-500ms t(p)+t(i)=T 3-6 times increased f=0.2/0.5hz Therapeutic effects Stim skin and smooth muscle Fibroblast and osteoblast stimulation Modulation of microcirculation Tissue regeneration
Indications of low frequency pulse currents
Hypotrophy? d/2 immobilization &
bone fractures-d/2 osteoblast stimulation
Muscle strengthen-Weak pelvic floor
Decrease spasticity by antagonistic muscle stim-Post stroke pt’s w/ spastic gait
Urinary incontinence
