INFRARED RADIATION

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.

  • 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)

1

mechanisms of heat transfer of the various modalities pic

The International Commission on Illumination (CIE)
describes IRR in terms of 3 biologically significant bands
.

  • 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)
  1. Production
  • 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.
  1. Sources

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.

Both require warm-up time.

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
  1. 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
  1. 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
    -
  • Muscle relaxation
    .
  • Increased blood supply

diag

  1. Application

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:

response of the subject.

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.

click to edit

  1. Dosage
  1. 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.

Foreign material / infection

Open wounds

  • increased tendency to develop adhesions.
  • Avoid dry heating.

Testicles

Apnoea:

infants (radiant warmers)

Optical damage:

corneal burns, retinal and lenticular injury

Susceptible subjects:

elderly, dehydration-lowering of BP-
dizziness and headaches.

Gangrene

  1. Contraindications
  • 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.
  1. Precautions, tests and warnings
  • A thermal skin test
  • The treatment can give rise to burns.

Advantages

Disadvantages

  1. Documentation
  • 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

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
    .
  • A Mild dose: skin temperature 36-38°C
  • A moderate dose: skin temperature 38-40°C
    .
     Duration: 10 to 20 minutes.