low frequency current - infra-red therapy

Question 1

how do electrical currents enter the body of the patient during therapy?

Answer 1

via electrodes placed on the surface of the tissue

Question 2

what are low frequency currents used for ?

Answer 2

-used as neuromuscular stimulators without the thermal effects

Question 3

what are the differences between a.c and d.c currents

Answer 3

-a.c current - direction of flow changes periodically, and oscillates back and forth
-d.c current -direction remains constant, does not oscillate - battery operating

Question 4

what is the charge density?

Answer 4

-amount of energy applied to the stimulated tissue per pulse

Question 5

in what 2 ways is direct current applied to tissue?

Answer 5

-either continuously
-or in a pulsed fashion

Question 6

what is a beat, in terms of low frequency currents?

Answer 6

when 2 slightly different are applied at the same time, resulting in overlapping
-if frequency of waves is close - there will be regions of constructive interference (where they add up)
- or if they are the same, they will cancel out - destructive interference

Question 7

are these waveforms a.c or d.c ?

Answer 7

a.c

Question 8

are these waveforms d.c or a.c?

Answer 8

d.c - as only in positive quadrant - therefore, the current flows in 1 direction

Question 9

if one high frequency a.c current of 4000 Hz interferes with a second HF a.c current of frequency 4150 Hz, what frequency of a current will it result in?

Answer 9

• 4150-4000 = 150Hz
  -low frequency LF current

Question 10

describe interferential therapy

Answer 10

-utilises 2 or more sinusoidal currents with slightly different frequencies. these currents are applied to the body via electrodes on skin
-when the currents overlap within the tissue, they create an interference pattern
-the interference pattern generated by the overlapping currents creates areas of high and low electrical intensity

Question 11

what is skin impedance?

Answer 11

• the electrical resistance of the skin to the flow of the electric current
  -how easily can a electric current pass through the skin

Question 12

compare high vs low skin impedance

Answer 12

high impedance = greater resistance, meaning that it is more difficult for current to pass through the skin
low impedance - means lower resistance, meaning that it is easier for current to pass through

Question 13

how do nerves react to this constant current & how dos IFT overcome this?

Answer 13

they will accommodate to a constant signal / current after a period of time - ie reduce its responsiveness
- to overcome this, a sweep of gradually changing frequency is often used during treatment - keeping nerves and muscles engaged

Question 14

why are frequency sweeps used in IFT?

Answer 14

-for optimising tissue penetration
-reducing accommodation of nerves

Question 15

what are examples of patterns of sweeps used in IFT?

Answer 15

• triangular sweep - ramp pattern - 90Hz - 130 Hz
  -rectangular sweep pattern
  -trapezoidal sweep

Question 16

what is transcutaneous electrical nerve stimulation (TENS)?

Answer 16

-method of low frequency electrical stimulation, which primarily aims to provide a degree of symptomatic pain relief by exciting sensory neurons and stimulating the pain gate mechanism
-0-80mA (current)

Question 17

what are different types of waveforms used in low freq treatments?

Answer 17

-symmetric biphasic - shape and amplitude of the pulse is identical in both pos and neg directions
-asymmetric bi-phasic - shape and amplitude of pulses are not identical in both directions

Question 18

is this a symmetric biphasic?

Answer 18

yes

Question 19

is this a assymetric vs symmetric biphasic wave form?

Answer 19

• asymmetric biphasic