10: Allied health devices

Question 1

Therapeutic ultrasound principles

Answer 1

• Limited evidence to suggest benefit- placebo effect??
• Generating ultrasound waves-
o AC voltage applied to crystal (crystal ceramic) in transducer
o Crystal vibrates, generating ultrasound waves
• Gel used to achieve impedance matching between transducer and skin
o Reduces reflection of sound by skin
• Beam modulation-
o Can be applied as continuous beam or pulsed to reduce cumulative heating effect

Question 2

Effects of therapeutic ultrasound

Answer 2

• Heating- increase blood flow&raquo_space; increase healing/reduced inflammation
• Non-heating-
o Acoustic streaming- mechanical pressure caused by US waves produces unidirectional fluid movement along cell membranes
o Cavitation- US waves cause microscopic gas bubbles in tissue to contract and expand- possible cellular death and local healing ??

Question 3

Treatment uses for US

Answer 3

• Pain relief
• Sports injuries
• Msk disorders
• Pain post amputation
• Leg ulcers
• Paediatric/geriatric disorders
• Chronic arthritis

Question 4

Shortwave diathermy principles

Answer 4

• 2 methods of applying-
o Capacitive method = condenser field
o Inductive method = coil (most common)
• Continuous or pulsed waves

Question 5

Capacitive method

Answer 5

• Part of body treated is placed between 2 condenser plates
• Energy passes through all body points between with resistance to E-field generating varying amounts of heat
• Localisation of energy absorption depends on electrode/skin spacing
o Small = surface
o Large = deeper

Question 6

Induction field

Answer 6

• Coils as electrodes applied to skin
• Electrical currents induced into surface tissues
• More effective for fatter patients
• Heats muscle and blood

Question 7

Uses of neuromuscular stimulation

Answer 7

• Determine whether muscle groups can contract
• Exercise muscle when normal stim is not available
• Regain function of paralysed muscles due to neurological injury
• Complex muscle function can be regained using programmed electrical stimulation (FES)

Question 8

Clinical use of neuromuscular stimulators

Answer 8

• Control of complex functions for movement
• Dropfoot prosthesis
• Using FES to help paraplegic patients stand, walk or climb stairs
• Urinary control systems
• Suppression of pain- gate-control theory

Question 9

General categories of pacemakers

Answer 9

• Asynchronous- not used anymore, maintained constant HR regardless of activity
• Synchronous- intermittent pacing for patients who can establish normal rhythm between periods of block
• Rate-responsive- stim rate controlled by measured physiological variables

Question 10

Current day pulse generators

Answer 10

• Power source- batteries
• Output circuit
• Timing circuit
• Sensing circuit
• Telemetry coil- provides info to clinician
• *all components housed in hermitically sealed titanium case