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INFRARED RADIATION, (Dosage, Hazards and Detrimental effects,…
INFRARED RADIATION
- Infrared radiation (IRR) is a superficial thermal agent used therapeutically for the relief of pain and stiffness, to increase joint motion and to enhance the healing of soft tissue lesions and skin conditons (Kitchen & Partridge 1991, Lehmann &
de Lateur 1999, Michlovitz 1986)
.
- IRR are electromagnetic waves with wavelengths of 750nm- 400000 nm. (0.78-1000μm)
.
- Any hot bodies emit IR to varying degrees
- Natural source (sun) or
- Artificial source (passing electrical current through a coiled resistance wire)
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The International Commission on Illumination (CIE)
describes IRR in terms of 3 biologically significant bands
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- IRA: Spectral values of 0.78-1.4μm
- IRB: Spectral values of 1.4-3.0μm
- IRC: Spectral values of 3.0-1.0μm
- For clinical use 0.7μm to 1.5μm
(concentrated in the IRA band)
- IR is produced as a result of molecular motion within materials.
An increase in temperature above absolute zero
results in the vibration or rotation of molecules within matter,
which leads to the emission of IRR
.
- The temperature of the body affects the wavelength of the radiation emitted.
Artificial IR
Non-Luminous generators
- commonly consist of a coiled resistance wire which is wound around or embedded in a
ceramic insulating material.
- Peak wavelength of around 4μm.
- Power levels 250 to 1000 W.
-
Luminous generators
- consist of a tungsten filament within a glass bulb which contains an inert gas at low pressure.
- They emit both IR and visible radiations with a
peak wavelength of around 1μm. Power levels 250 to 1500 W
- Physical behaviour of IRR
- IR can be reflected, absorbed, transmitted, refracted and diffracted by matter
.
- The reflection and absorption being of most biological and clinical significance.
Absorption
IR must be absorbed to facilitate changes within the body tissues
.
Absorption depends on
- The structure and type of tissue
- Vascularity and
- pigmentation
Penetration
Penetration of energy into a medium is depend upon
- Intensity of the source of infrared
- Wavelength
- Angle at which the radiation hits the surface
- Coefficient of absorption of the material.
- Maximum penetration: 1.2 μm
- The skin is virtually opaque to wavelengths of 2μm
- Superficial heating
- All energy was absorbed at a depth of 2.5mm (0.1 mm longer wavelength to 3 mm shorter wavelength)
Heating of body tissue
- IR-thermal changes owing to the absorption of radiation which leads to molecular vibration, and this motion in turn leads to the thermal changes
.
- Heating at greater depth-direct conduction and by convection –increased local circulation.
effects of heat
- Incr local temp superficially
- incr local metabolism
- vasodilation of arterioles & capillaries
- incr blood flow to part heted
- increased leukocytes & phagocytosis
- incr capillary permeability
- incr lymphatic & venous drainage
- incr metabolic wastes
- incr axon reflex activity
- incr elasticity of ms, ligaments & capsule, fibers
- analgesia
- incr formation of edema
- decr ms tone
- decr ms spasm
- Clinical efficacy (Therapeutic effects)
- Pain – ulnar nerve at elbow- analgesic effect – distal to the point of application
.
- Increase in the conduction velocity of normal nerves in humans
.
- Joint stiffness – small joints like hand
.
- Oedema –vasodilation
.
- Skin lesions –
Fungal infections-Paronychia and psoriasis
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- Muscle relaxation
.
- Increased blood supply
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Before treatment
- inspect the body part for contraindications, an explanation and safety warnings given.
- Select and warm up equipment
(non-luminous-15 minutes;
luminous- a few minutes only)
Patient:
- a comfortable, supported position.
- The skin should be uncovered, clean and dry, all liniments and creams having been removed.
Safety precautions
Lamp position:
at a right-angle to the skin (but not directly
above a part to avoid burns should it fall) Distance: between 50 and 75 cm.
Dosage:
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Follow-up
- Following the cessation of treatment, the temperature of the skin should feel mildly or moderately warm to touch.
- The degree of erythema induced should be
noted and any unexpected changes evaluated.
At the end of this unit the student will be able to explain
Definition of infrared radiation and the place in electromagnetic
spectrum.
Production of infrared radiation.
Types of generators – Luminous and Non-luminous
Indication and Contraindication.
Physiological and Therapeutic effect of Infrared radiation.
Dangers.
Choice of apparatus.
Arrangement of lamp and patient.
Preparation of patient.
Application of treatment.
Treatment frequency and duration.
The amount of energy received will be governed by the
- Intensity of the output of the lamp (in watts)
- Distance of the lamp from the patient
- Duration of the treatment
.
For therapeutic effect- temperature of between 40 and 45°C to be maintained for at least 5 minutes
.
At the end of treatment
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- A Mild dose: skin temperature 36-38°C
- A moderate dose: skin temperature 38-40°C
.
Duration: 10 to 20 minutes.
- Hazards and Detrimental effects
Burns:
- Inadequate testing of materials and equipment
- The tissue is devitalized
- The patient has severely impaired skin sensation and is unable to note overheating.
- Exposure of 46-47°C and above
- Electric burn
Electric shock
Chronic damage to tissue
Prolonged exposure to IR at higher,
tolerable temperatures. Permanent pigmentation.
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- Lack of local thermal sensitivity on the part of the patient
- Local areas of recent bleeding
- Subjects with advanced cardiovascular disease
- Subjects with a reduced level of consciousness or understanding of the dangers of treatment
- Subjects with acute febrile illness.
- Devitalized skin e.g. after deep X-ray treatment.
- Certain skin conditions: e.g. skin carcinomas, acute dermatitis.
- Caution:
-Impaired local circulation
-Damaged or infected tissues: moist heat may encourage breakdown.
- Precautions, tests and warnings
- A thermal skin test
- The treatment can give rise to burns.
- The area of the body treated
- The type of heating agent used
- The treatment duration
- The response to treatment
- Treatment parameters such as the temperature or power of the agent,
- The number and type of insulation layers used
- The distance of the agent from the patient,
- The patient’s position or activity
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