Week 10 (Ultrasound) Flashcards
Use of electrical stimulation
Motor: muscle re-education, muscle strengthening
Sensory: pain management, reducing muscle spasticity
Other: promote blood flow, facilitate wound and fracture healing, reduce oedema
Contraindications to IFT and TENS
- Within 3 metres of operating shortwave diathermy
- Transthoracic application
- Cardiac pacemaker or any other inbuilt stimulator
- Overpregnant utertus
- Inability to communicate
- Sensory loss
Precautions to IFT and TENS
- Broken skin
- Metal implants
- Circulatory insufficiency
- Exacerbation of existing conditions (e.g. acute infections, recent radiotherapy, etc.)
- Risk of dissemination (e.g. acute infections, tumours, etc.)
Effects of TENS
Stimulates AB fibres reducing transmission of nociceptive signals through
- Activating inhibitory interneurons in the dorsal horn (high frequency TENS >50Hz) toning down activity in inhibitory interneurons
- Release of endogenous opioids that inhibit c-fibres (low frequency TENS 1-10Hz) inhibits descending modulation pathways helping tone down sensitisation
Parameters of TENS
Longer pulse durations stimulate Ab fibres
- High frequency: 50Hz (usually 80-150Hz) (pain gate mechanism)
- Low frequency: 1-10Hz (endogenous opioid mechanism)
- Treatment: 30 min or more
Evidence of TENS
- Chronic MSK pain
- Knee OA
- Post-operative pain
- Equal/more effective than NSAIDS
Proposed physiological effects of ultrasound
Thermal
- Deep heating
Non-thermal
- Cavitation: formation of tiny gas bubbles altering permeability of cell membrane
- 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
Proposed therapeutic effects of ultrasound
- Might increase healing of chronic pressure ulcers
- Might increase healing of soft tissue injuries
- Could improve extensibility of scar tissue
- Could improve fracture healing – requires low intensity pulsed ultrasound
Safety considerations of ultrasound
- Burns due to poor technique
- Tissue damage at high intensities
- Periosteal pain near bony prominences
Contraindications to ultrasound
- Near cardiac pacemaker or any other inbuilt stimulator
- Circulatory insufficiency
- Exacerbation of existing conditions (e.g. acute infections, recent radiotherapy, etc.)
- Risk of dissemination (e.g. acute infections, tumours, etc.)
- Application to eyes or testes or over a pregnant uterus
- Inability to communicate
- Sensory loss
Parameters of ultrasound
- Method: direct contact or water bath
- Mode: continuous or period
- Frequency: 1 or 3 MHz
- 1 MHz for deeper tissues (approx. 6cm)
- 3 MHz for superficial structures (approx.. 3cm)
- Duration: usually 5-10 min per treatment area (twice the area of the applicator head)
- Intensity: in Watts/cm2
- Acute and subacute: 0.1-0.5 W/cm2
- Chronic: 0.8 – 3W/cm2
- Lower intensity used if high frequency i.e. if using 3 MHz, reduce intensity by factor of 3
Evidence for IFT
Little evidence: tissue heterogeneity and orientation of nerve fibres influences stimulation
- Effective as supplementary treatment for MSK pain but only in the short-term
