Shortwave Diathermy Chapter 9 Description • High-frequency electrical currents – Radio waves • • • • • Pass through the tissues Cause molecular vibration Results in deep heating Capable of heating large volumes of tissues Causes both thermal and nonthermal effects Uses Thermal Effects • Deep heat • Increased blood flow • Increased cell metabolism • Increased tissue extensibility • Muscular relaxation • Possible changes in enzyme reactions Nonthermal Effects • Edema reduction • Lymphedema reduction • Superficial wound healing • Treatment of venous stasis ulcers Types of Shortwave Diathermy Induction Field Capacitive Field Induction Field Diathermy • Places the patient in the electromagnetic field • Selectively heats muscle • Also referred to as: – Condenser field diathermy – Magnetic field diathermy Induction Field Diathermy (Cont.) • A coil is housed within a drum • Current flowing within the coil produces a rotating magnetic field • Magnetic field produces eddy currents in the tissues • Eddy currents cause friction that produce heat • Although rare, cables are sometimes used in place of drums Capacitive Field Diathermy • Uses the patient’s tissues as a part of the circuit • The tissues’ electrical resistance produces heat • Selectively heats skin – Muscle is heated via conduction from the adipose • Also referred to as “condenser field diathermy” Capacitive Field Diathermy (Cont.) • Heat is produced by the dipole effect • Charge particles within membrane align with the field • The movement produces heat + + - + - + + - + - Modes of Application Continuous • Increases tissue temperature • Increased risk of burns Pulsed • May or may not increase temperature • Pulses allow for increased treatment intensity and duration • Not the same as “nonthermal” Ultrasound & SWD Comparison Energy type Tissue heated Tissue volume Temp increase Heat retention C = Capacitive method I = Induction method Ultrasound Acoustical Collage-rich Small (20 cm2) 1 MHz: > 6.3°F 3 MHz: > 14.9°F 3 min Shortwave Diathermy Electromagnetic C: Skin, adipose tissue I: Muscle, vessels Large (200 cm2) C: > 7°F I: > 18°F > 9 min Biophysical Effects Inflammation • Assists in removal of cellular debris and toxins • Nonthermal: – Alters diffusion rate across the cell membrane • Thermal – Increases intramuscular metabolism Biophysical Effects Blood and Fluid Dynamics • Vasodilation increases: – – – – Blood flow Capillary filtration Capillary pressure Oxygen perfusion • Increased fibroblastic activity and capillary growth • Effects occur deeper than other forms of heat Biophysical Effects Tissue Elasticity • SWD can vigorously heat deep tissues • Alters collagen properties, allowing it to elongate • Requires stretching during and/or immediately following the treatment • Multiple treatments are required Biophysical Effects Wound Healing • Nonthermal SWD increases rate of phagocytosis • Number of mature collage bundles increase • ATP activity increases (assisting wound regeneration) • Necrosed muscle fibers decrease Contraindications • • • • • Metal implants or metal jewelry Cardiac pacemakers Ischemic areas Peripheral vascular disease Perspiration and moist dressings: The water collects and concentrates the heat. • Tendency to hemorrhage, including menstruation. • Pregnancy • Fever • Sensory loss • Cancer • Areas of particular sensitivity: – – – – Epiphyseal plates in children The genitals Sites of infection The abdomen with an implanted intrauterine device (IUD) – The eyes and face – Application through the skull