Infrared
Infrared type of electromagnetic radiation is absorbed in the range
of 7.700 A° units to approximately 150.000 A° units. Absorption takes
place within the top 3 mm of skin.
Physics:
Glowing substances such as heaters and light bulbs emit infrared
radiation, which can affect heat-sensitive tissues. Using devices emitting
infrared radiation, target distance and angulation of the projected
radiation have to be monitored. Reduction of heat produced can be
accomplished by:
- Increasing the distance from the patient’s skin.
- Increasing the angle at which the radiation strikes the skin.
Sources:
Any hot body emits infrared rays, so there are many sources of
these rays such as the sun, gas and coal. Two types of sources of heat are
present:
1. Luminous units: They are short-wave infrared. They emit infrared
radiation, derived from glowing sources such as hot wires and various
types of bulbs.
2. Non-luminous units: They are long-wave infrared. They emit
infrared radiation, derived from non-glowing sources such as radiators
and hot packs.
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Physiological effects:
Both types of infrared radiation share in the physiological effects
but non-luminous units apparently feel hotter than do luminous ones, if
both are at equal distance and power level. This may be due to the
increased absorption of the longer wavelengths by the top skin layers.
Irradiation from infrared results in the production of heat in the
superficial tissues and the heat is carried to the deeper tissues by
conduction and by the circulating fluids.
* Increased metabolism: It results in increased demands to oxygen and
food staffs and increased output of waste products.
* Vasodilatation: There is dilatation of capillaries and arterioles in the
superficial sensory nerve endings, which causes reflex vasodilatation.
* Pigmentation: Repeated exposure to infrared rays produces erythematic
redness, which is mottled in appearance.
* Sedation: While mild heating has a sedative effect on sensory nerve
endings, more intense heating will have an irritating effect.
* Increase efficiency of muscle action: Rise in temperature causes muscle
fibers to contract and relax more quickly.
* General rise in temperature: When extensive and prolonged treatment
is applied, generalized dilatation of superficial blood vessels occurs.
* Fall in blood pressure: Generalized vasodilatation reduces peripheral
resistance and blood viscosity, which tend to reduce bleed pressure.
* Increased activity of the sweat glands: The heated blood circulates
throughout the body, affecting the centers concerned with regulation of
temperature, which leads to increasing the activity of sweat glands.
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Indications:
* Relief of pain:
Mild heat relieves pain due to its sedative effects on superficial
nerve endings, while stronger heat relives pain via counter-irritation,
resulting from irritation of superficial nerve endings. Intensive treatment
may produce an increased exudation of fluids into the tissues and so,
increases pain.
* Muscle relaxation:
Warming the tissue results in rapid muscle relaxation, which helps
in relieving muscle spasm.
* Increased blood supply:
Infrared may be used in treatment of superficial wounds and
infections, as good blood supply is essential in the healing process.
* Elimination of waste products:
As intensive treatment causes increased activity of sweat glands,
infrared may be used in the treatment of arthritis due to elimination of
waste products.
* Adjunctive therapy:
Infrared can be used prior to other physical therapy modalities,
especially in cold weather.
Contraindications:
- Impairment of skin sensation.
- Pathological skin conditions.
- Prolonged exposure to the eyes.
- Hemorrhage.
- Defective arterial blood pressure.
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Treatment procedures:
* Luminous units:
They are utilized most in chronic inflammations. Generally, the
luminous units are placed directly over the target area at a distance of 24
to 36 inches. The duration of treatment ranges from 20 to 30 minutes,
according to the skin sensitivity of the target area, to be applied daily or
every other day.
* Non-luminous units:
They are preferred in acute inflammations or recent injuries for the
sedative effect of the long-wave infrared. As the non-luminous units
usually feel hotter than luminous ones, they should be placed at a greater
distance (30 to 42 inches) and at an angle of 45°, for 10 to 15 minutes.
Treatment may be applied several times during the day.
* Tunnel bath:
They are preferred in treatment of chronic cases, when several
areas to be treated. It is a big piece of wood or metal, made like a tunnel,
having a length of about ½ to 1 meter. The infrared lamps are fixed in
rows inside the tunnel, which is placed on the target area. Treatment
duration ranges from 20 to 30 minutes, to be applied every other day.
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