23 Summer PHT2025

PHT2025 Science and Practice of Electrotherapy

2023/6/26

1. ensure normal skin sensation response (so that pt can feel the Rx)

2. prevent development of potential injuries

Why

1. 1st time application of the modality

2. maybe major change of pt conditions

When

Skin sensation tests

Thermotherapy

Effects:

1. vasodilation

2. increase metabolism

3. increase nerve conduction velocity

4. increase collagen extensibility

Fill in the Blanks

Thermotherapy cannot exceed the temperature of

°C.

Open Ended

Suggested timing of application of superficial heating is around 15-20 minutes. Why?

Thermotherapy

When superficial heat applied:

1. max temp at 8-10 min

2. stable at 20 min

   1. no extra benefit in increase of time

   2. heating agent not hot anymore

3. heat will accumulate --> be aware of delayed response

Fill in the Blanks

In H/C test, hot test tube / cold test tube:

__°C /__°C ?

SWD over hot pack

Advantages

1. target tissue: deep vs superficial (2cm)

2. more prolonged heating effect (effective after Rx x 20-30 min)

Multiple Select

Which of the followings are true about Lewis Hunting reaction?

• induce vasodilation

• prevent tissue damage during cryotherapy

• cause burning sensation when applying cryotherapy

• overall vasoconstriction in net effect

Open Ended

What are the possible skin sensations when applying cryotherapy?

Cryotherapy

Skin sensations

1. coldness

2. burning

3. pain

4. numbness / mild anesthesia

optimal temp: 10-15°C

US

Transmission

1. efficiency: air < water/muscle/fat < bone
   --> need coupling medium + be aware of periosteum pain

2. nonuniform beam
   --> peak intensity at perpendicular distance + continuous movt to ensure even distribution

3. 3MHz --> superficial & 1 MHz --> deeper (intensity *2 to compensate to half value depth)

Nerve conduction

Properties

1. refractory period: absolute - 1ms, relative - 10ms

2. all or none: stimulation must reach threshold

3. impulse velocity: faster in larger diameter / myelinated fibre

Multiple Choice

The difference btw voluntary contraction (a) and ES induced contraction (b)?

• a: recruit small fibres before large

  b: large before small

• a: synchronous firing

  b: asynchronous firing

Multiple Choice

Can suction cup applied to pt with swelling?

• Y

• N

• Y & N

Suction cup

In swelling pt

1. acute swelling --> NO

2. chronic / subacute --> YES

3. bruising --> NO

Fill in the Blanks

Pain gate theory: selectively depolarise _____ fibres

Opiate system: selectively depolarise _____ fibres

(Hints: about size)

1. depolarise small fibre (A-delta/C: nociception)

2. inhibition of pain-transmitting cells in brain by endogenous opiate substance

Opiate system

1. depolarise large fibre (A-beta: tactile sensation)

2. temporary inhibition of pain-transmitting cells in spinal cord

Pain gate

Pain modulation

Multiple Select

What parameters would you set for pt in acute pain aiming at instant pain relief?

• high frequency

• low intensity

• low frequency

• high intensity

1. ​Sensory

   1. High frequency = short pulse duration

   2. AND Low intensity (current amplitude)

2. Motor

   1. Lower frequency

   2. AND Higher intensity (current amplitude)

3. Pain

   1. Very low frequency = long pulse duration

   2. OR high intensity (current amplitude)

Strength Duration Curve