Lecture 9 - sensory electrical stimulation and therapeutic ultrasound

Question 1

Use of electrical stimulation

Answer 1

Motor:

• muscle re-educating
• muscle strengthening

Sensory:

• pain management
• reducing muscle spasticity

Other:

• promote blood flow
• facilitate wound and fracture healing
• reduce oedema

Question 2

Voltage

Answer 2

difference in electrical potential energy between two points in a circuit (volts)

Question 3

Current

Answer 3

amount of electrical charge flowing through the circuit (amps)

Question 4

Resistance

Answer 4

a materials tendency to resist the flow of electrical charge

Question 5

Types of currents

Answer 5

Direct currents (DC)
Pulsed currents
Alternating current

Question 6

Electrical stimulation parameters

Answer 6

• pulse amplitude
• frequency
• pulse duration

Question 7

Pulse amplitude

Answer 7

strength of stimulus (mA or V)

Question 8

Frequency

Answer 8

the number of pulses delivered per second

Question 9

Pulse duration/width

Answer 9

length of each electrical impulse (us or ms)

Question 10

Selective stimulation of nerves fibres - order of stimulation

Answer 10

1. non-noxious sensory
2. Motor
3. Noxious sensory

Question 11

Sensory electrical stimulation methods/ 3 components

Answer 11

Interferential therapy (IFT)
Portable transcutaneous electrical nerve stimulation (TENS) machine

components:

1. power source
2. stimulator
3. electrodes and leads

Question 12

Contraindications of electrical stimulation

Answer 12

• within 3m of operating shortwave diathermy (SWD)
• transthoracic application
• cardiac pacemaker
• pregnant
• inability to communicate
• sensory loss

Question 13

Precautions of electrical stimulation

Answer 13

• broken skin
• metal implants
• circulatory insufficiency
• exacerbation of existing conditions
• risk of dissemination

Question 14

Safety skin check

Answer 14

sharp/blunt discrimination test using pen

Question 15

Portable TENS

Answer 15

portable, battery operated type of sensory electrical stimulation
- uses pulsed currents

Question 16

Effects of TENS

Answer 16

Stimulating AB fibres - can reduce the transmission of nociceptive signals by activating inhibitory interneurons in dorsal horn

Stimulating AD fibres - reduce transmission of nociceptive signals through the release of endogenous opioids that inhibit C-fibres

Question 17

TENS parameters

Answer 17

longer pulse durations stimulate AD fibres

High frequency (>50Hz) - pain gate mechanism

Low frequency (1-10Hz) - endogenous opioid mechanism

Question 18

Treatment time

Answer 18

30 mins or more

Question 19

Current intensity

Answer 19

• strong tingling but below motor threshold (high frequency TENS)
• At or above motor threshold (low frequency TENS)

Question 20

Mode

Answer 20

B: burst stim
N: constant stim
M: modulation stim

Question 21

Tolerance to TENS

Answer 21

Because the effects are opioid mediated, repeated use of TENS can produce tolerance to analgesic effects’

can be delayed by alternating between high frequency and low frequency

Question 22

Interferential therapy (IFT)

Answer 22

application of two medium frequency (kHz) alternating currents (AC) by 2 pairs of electrodes to the surface of the skin, positioned diagonally opposed to each other

Two currents have slightly different frequency, and so “interfere” or intersect deep within the tissues

Question 23

What is ultrasound?

Answer 23

• a type of mechanical vibration
• longitudinal waves made up of a series of mechanical compressions and rarefactions
• requires a medium to travel

Question 24

ultrasound reflection

Answer 24

some of the energy is reflected back and the remainder is refracted

Question 25

Physiological effects of ultrasound

Answer 25

Thermal:
- deep heating

Non Thermal:
- cavitation: formation of tiny gas bubbles altering permeability of cell membranes

• standing waves: superimposed waves with peaks of high and low pressure
• acoustic streaming: bulk streaming and microstreaming that washes away ions and molecules accumulated on the outside of the cell
• micromassage: changes in pressure on the cell and tissue

Question 26

Pulsed ultrasound

Answer 26

• reduces the heat effect but still produced the mechanical effects
• duty cycle
• pulse ratio

Question 27

Proposed therapeutic benefits

Answer 27

• healing of chronic pressure ulcers
• healing of soft tissue injuries
• extensibility of tissue
• fracture healing - requires low intensity pulsed ultrasound

Question 28

Ultrasound parameters

Answer 28

method: direct contact or water bath

Mode: continuous or pulsed

Frequency: 1 (deeper) or 3 (superficial) MHZ

Duration: 5-10 mins per treatment area

Intensity:

• acute & subacute: 0.1 - 0.5
• chronic: 0.8 - 3