Electrophysical agents: Shortwave Diathermy

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Shortwave Diathermy : 

Shortwave Diathermy Dr Shea Palmer (Content) Mr Chee-Wee Tan (Narration)

Shortwave Diathermy (SWD) : 

Shortwave Diathermy (SWD) Shortwave electromagnetic (EM) radiation - radio frequency waves Therapeutic diathermy set at 27.12MHz Pulsed SWD - a method of rapidly switching on and off the EM field Used to deliver heat and ‘energy’ to deeply situated tissues


PSWD Developed due to belief that non-thermal effects of SWD existed, but masked by  heat Same as SWD but pulsed - allows heat dispersal. Large possible selection of treatment parameters - optimum settings to be established

What is EM energy? : 

What is EM energy? Electric field: Exists between and around charged particles, e.g. protons/electrons. moving electrical charges = electric current Magnetic field: Magnetic force generated at 90° to the current Area where this force acts = magnetic field

Tissue Response : 

Tissue Response Shortwave EM energy  little effect on tissue itself, but……. SWD EM field creates tiny electric currents  a magnetic field within tissues i.e., both electrical and magnetic fields set up in human tissue subjected to SWD These fields  physiological effects

Production of SWD : 

Production of SWD Patient made part of the electrical circuit by the use of either: An inductive coil - magnetic field radiated at right angles to direction of current flow producing small eddy currents in tissues Capacitive type electrodes - SWD field is generated between two electrodes and body part being treated acts as dielectric

Methods of Heat Production : 

Methods of Heat Production Living tissue consists of 3 molecule /particle types: Charged molecules (ions, Na+, some proteins) Dipolar Molecules (water, some proteins) Non polar molecules (fat)

1. Charged molecules/particles : 

1. Charged molecules/particles Na+, some proteins Attraction/repulsion forces between charged molecules compel them to accelerate along the lines of electrical force Causes collisions & loss of kinetic energy  heat production (most efficient)

2. Dipolar Molecules : 

2. Dipolar Molecules H2O, some proteins Positive orientated towards negative Alternating field - produces rotation  heat production (moderately efficient)

3. Non-Polar Molecules : 

3. Non-Polar Molecules Fat Alternating field causes electron clouds to move back & forth Temperature  due to blood electrolytes - fat then insulates heat  heat production (least efficient)

Application of SWD : 

Application of SWD Inductive Method Circuplode/Flexiplode Deeper heating Coil within drum: 2cm spacing (towel between drum and skin)

Slide 12: 

Capacitor method Plate electrodes: contra-planar / coplanar Superficial heating Distribution depends on: Size & position of electrodes Tissue types: (fat  conductivity) Tissue shape Electrode spacing: wider  even heating (2-4cm)

Dosage : 

Dosage Little evidence / agreement Average power useful: pulse duration x pulse frequency x peak pulse power Evidence suggests that longer times with high frequencies & short pulses most effective Time 20-30min (empirical - ? habitual)

Slide 14: 

Mean power = pulse duration x pulse frequency x peak pulse power (see hand-out of table illustrating mean power) Acute - low mean power Subacute - medium mean power Chronic - high mean power

Therapeutic Effects : 

Therapeutic Effects Thermal blood flow  inflammation  Collagen extensibility  Joint stiffness  Pain  Muscle spasm

Slide 16: 

Athermal Possible  rate of soft tissue healing  number & activity of cells in injured area  haematoma reabsorption  Swelling  fibrin and collagen deposition/orientation  nerve growth & repair

Patient Preparation : 

Patient Preparation Explain - degree of heat, treatment aims Warn to notify if any problems Contraindications Remove hearing aids Expose area SKIN TESTING Positioning: dry area, *care with metal Test - neon tube Switch on, tune &  to desired intensity

Contraindications : 

Contraindications Implanted pacemakers Metal in tissues or external fixators Lack of thermal sensitivity Uncooperative patients Pregnancy Haemorrhaging areas (may be temporary increase in bleeding during menstruation if pelvis irradiated)

Slide 19: 

Ischaemic tissue Malignant tumors Active tuberculosis Recent venous thrombosis Pyrexia Devitalised skin (e.g. after deep X-ray treatment) Growing epiphysis Scott (2002) pp. 162

Research Evidence : 

Research Evidence Some positive effects – soft tissue healing, haematoma resolution, recent ankle injuries, pain, nerve regeneration and OA Little research carried out and of poor quality Definitive conclusions to be determined

Summary : 

Summary Magnetic radiation Used to cause deep heating and tissue healing Research evidence still to mature – may be hampered by fall in popularity

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