Infrared rays Definition .
Infrared radiation therapy is the application of Infrared rays over affected area or conditions mention in indications of this post . The infrared rays are electromagnetic waves with the wavelengths of 750 to 400000 nm and frequency 4 × 1014 Hz and 7.5 × 1011 Hz. It lies beyond the red boundary of visible spectrum. Any hot body can produce infrared rays like the sun, electric bulb, coal fire, gas fire, etc.
Infrared rays are also called thermiogenic rays, since these rays produce heat when they are absorbed by the body tissue. Sun is the natural source of infrared radiations. Infrared radiations can be produced by artificial generators. In the Physiotherapy departments infrared rays are produced by two types of generators:
1. Nonluminous generators .
2. Luminous generators.
Nonluminous generators provide infrared rays only whereas luminous generators emit infrared rays, visible as well as ultraviolet rays. Therefore, nonluminous generators are termed as infrared radiation generators because they emit only infrared rays. The heat produced by luminous generator is called the ‘radiant heat’.
Classification of Infrared rays .
Depending on wavelength, infrared rays are classified as short-wave infrared and long-wave infrared. Short-wave infrared rays are also called near infrared rays. Wavelength of short-wave infrared rays ranges in between 750 to 1,500 nm. Long-wave infrared rays are also called far infrared rays. Wavelength of these rays is above 1,500 nm.
Infrared rays are also classified as, infrared A, B and C. Infrared A have wavelength between 750 to 1,400 nm, wavelength of infrared B is in the range of 1,400 to 3,000 nm and wavelength of infrared C ranges between 3,000 nm to 1 mm.
Production of Infrared radiation .
Any body with high temperature than the surrounding can emit infrared rays and hence, sun is mainly the natural source of infrared radiation. However, in physiotherapy, various types of artificial infrared generators are used, for practical purposes. These generators can be divided into two types namely, non-luminous and luminous.
1. Non-luminous Generators .
Non-luminous generators are also called low temperature generators. These generators produce only infrared rays and hence, they are not visible. These generators are heated by the passage of electric current through a bare wire or carbon, held in a suitable non-conducting material like porcelain, mounted at the center of a parabolic reflector.
Small non-luminous units draw 50 to 300 watts of power and larger ones draw up to 1,500 watts. These generators emit only infrared rays. All non-luminous generators emit infrared rays in between 750 to 15,000 nm. The maximum emission of the rays is around 4,000 nm.
2. Luminous Generator .
Luminous generators are also called high temperature generators. Luminous generators emit visible rays, ultraviolet rays and infrared rays and hence, they are visible. These generators are in the form of incandescent bulbs. An incandescent bulb consists of a wire filament enclosed in a glass bulb, which may or may not contain inert gas at low pressure.
The filament is a coil of fine wires usually made of tungsten. This material tolerates repeated heating and cooling. The exclusion of air prevents the oxidation of filament, which would cause an opaque deposit to form inside the bulb. The wattage of the bulb may vary from 60 to 1,000 watts, though the use of bulbs with higher wattage is discouraged because of the danger of explosion during the treatment.
Incandescent bulb is generally mounted at the center of the parabolic reflector and the reflector is mounted on an adjustable stand. All luminous generators emit electromagnetic waves with the wavelength in between 350 to 4,000 nm, but the maximum emission of the rays is around 1,000 nm. Accessories such as localizers, filters to filter out ultraviolet rays and visible rays were used commonly in the past. However, nowadays, only one accessory in the form of variable resistance may be used so as to control the intensity of infrared rays.
Techniques of the Treatment .
1. The choice of apparatus .
In most cases luminous and nonluminous generators are equally suitable, but in some instances one proves more satisfactory than the other. When there is acute inflammation or recent injury, the sedative effect of rays obtained from nonluminous generator may prove more effective for relieving pain than the counter-irritant effect of those from the luminous source.
For lesions of a more chronic type, the counter-irritant effect of the shorter rays may prove to be of value, and under these circumstances a luminous generator is chosen. Selection of the generator according to the area to be treated is done. If only one surface is to be treated, a lamp of a single element mounted on a reflector is used. If several aspects are required to be irradiated, a tunnel bath is more effective.
The temperature reached in a tunnel bath is higher than produced by other lamps and this may be advantage if chronic lesions are to be treated. Before application the lamp must be checked to ensure that it is working correctly. Nonluminous generators must be switched on an adequate time before application.
2. Preparation of the Patient .
The clothes must be removed from the area to be treated and skin is checked for its sensation against heat and cold. It is unwise to give treatment if the skin sensation is found defective. The patient should be comfortable and fully supported so that he does not move unduly during treatment. The patient is warned that he should experience comfortable warmth and he should report immediately if the heating become excessive as undue heat may cause burn. He should be instructed not to touch the apparatus and nor to move nearer to the apparatus.
3. Arrangement of the lamp and patient .
The lamp is positioned so that it is opposite to the center of the area to be treated and the rays strike the skin at the right angle thus ensuring maximum absorption. The distance of the lamp from the patient should be measured. Optimum distance is around 50–75 cm depending upon the output of the generator. Care must be taken that the patient’s face is not exposed to infrared rays, eyes must be shielded to avoid this.
Application of infrared treatment .
At the start of the treatment exposure the intensity of the radiation should be low, but after 5–10 minutes when vasodilatation has taken place and the increased blood flow has become established, the strength of the radiation may be increased. This can be achieved by moving the lamp closer to the patient or by adjusting the variable resistance.
The physiotherapist should be near the patient throughout the treatment session and should reduce the intensity of radiation if the heat becomes excessive. If the irradiation is extensive, it is desirable that sweating should occur to counteract any excess rise in body temperature. Sweating is encouraged if the patient is provided water to drink during treatment. At the end of the treatment the skin should be mild red, not excessively red.
After extensive irradiation the patient should not rise suddenly from the recumbent position or go out into the cold immediately. Duration and frequency of treatment: In cases of acute inflammation or recent injuries and for the treatment of wounds, an exposure of 10–15 minutes is adequate, but it may be applied several times during the day. In cases of chronic conditions longer exposures may be used.
Depth of Penetration of Rays .
Luminous generator produces infrared rays having wavelength between 350 and 4000 nm. It can penetrate into dermis and epidermis of the subcutaneous tissue. Nonluminous generator produces infrared rays of wavelength 750 to 15000 nm which can penetrate the superficial dermis only. The depth of the penetration depends upon the wavelength and the nature of the material . Thus, infrared rays produced from a luminous generator have more penetration power than that produced from nonluminous generator.
Laws Regulating the Absorption of Radiation .
Various laws regulating the absorption of radiations including infrared rays are Grothus law, law of inverse square, cosine law, BeerLambert law, Kirchhoff’s law, Wien’s law, Stefan-Boltzmann law and Arndt-Schultz principle.
1. Grothus Law .
Grothus law is also known as Grothus-Draper law. It states that, the rays must be absorbed to produce the effect and the effect will be produced at the point at which the rays are absorbed. I always explain this law to my students with a very simple analogy. I say you will pass the exam provided you will study and you will pass those subjects which you study. In another words, to pass you should study, but by studying electrotherapy, you will pass only in electrotherapy and not in any other subject. Although, this is not a perfect analogy, it helps me explain the law to my students.
2. Law of Inverse Square .
Law of inverse square explains the effect of distance on the intensity of infrared rays. It states that the intensity of a beam of rays, from a point source, is inversely proportional to the square of the distance from the source.
3 Cosine Law .
Cosine law is also known as Lambert’s Cosine law. Cosine law explains the effect of angle at which the rays strike. It states that the proportion of rays absorbed varies as per the cosine of the angle between incident and normal. Thus, larger the angle at which the rays strike to the body surface, lesser will be the absorption and vice versa.
If the rays strike at 90º to the body part then angle between the incident and normal or perpendicular will be zero and the cosine of 0º is maximum, that is one. Thus, there will be maximum absorption, if the rays will strike the body part at 90º as per this law. Hence, we always try to apply the infrared rays in such a way that they strike at the 90° angles to the body part to be treated.
4. Beer-Lambert Law .
Degree of absorption depends on the wavelengths of radiation and nature of the absorbing material.
5. Kirchhoff’s Law .
Kirchhoff’s law states that good radiators are good absorbers.
6. Wien’s Law .
Wien’s law states that the wavelength of maximal emission is inversely proportional to the absolute temperature of the source, so that hotter the source, shorter is the wavelength of emitted rays.
7. Stefan-Boltzman Law .
Stefan, Boltzman law states that the output of the infrared lamp will depend on the temperature of the element and its radiating area.
8. Arndt- Schultz Principle .
Arndt-Schultz principle states three things. Addition of a sub-threshold quantity of energy will not cause a demonstrable change, addition of threshold and above quantity of energy will stimulate the absorbing tissue to normal function and if too great a quantity of energy is absorbed, then added energy will prevent normal function or destroy tissue.
Dosages of Infrared Rays .
For acute cases, irradiation with infrared rays can be given for 10 to 15 minutes daily, for one to three times as per the requirement. For chronic cases, up to 30 minutes once daily or on alternate days can be given. The infrared generator is arranged in such a position so that, it is opposite to the center of the area to be treated and the rays strike at right angles.
Irradiation can be applied at a distance of 50 to 75 cm. During irradiation of the face, cover the face, eyes and hair. Eyes should be protected by moist cotton packs, otherwise opacities of lens may occur.
Uses & Indications of Infrared radiation .
Infrared rays are commonly used in the treatment of subacute and chronic inflammatory conditions, in areas which are accessible to exposure. Various forms of arthritis such as, osteoarthritis and rheumatoid arthritis where joints are painful and the pressure by other modalities like hot packs, etc. on it, must be avoided, then infrared rays can be a treatment of choice. Skin conditions such as furunculosis, folliculitis, etc. can be treated with infrared rays.
Infrared rays can be used as a preliminary modality before stretching exercises. It can also be used in the treatment of Bell’s palsy for the relief of pain at the root of ear. Infrared rays application in Bell’s palsy may also be of a value since it may produce perspiration which will reduce the skin resistance and facilitate electrical stimulation of facial muscles. Muscle spasm of traumatic and non-traumatic orthopedic origin can also be very well treated with infrared rays.
- Acute & Subacute Pain .
- Chronic Pain .
- Osteoarthritis .
- Rheumatoid arthritis .
- Skin conditions such as furunculosis, folliculitis, etc .
- Bell’s palsy .
- Psoriasis .
- Joint Stiffness .
- Oedema .
- Capsulitis .
- Inflammatory Conditions .
- Muscle Spasm .
Contraindications of Infrared radiation .
- Fever .
- Pelvic region in pregnancy .
- Over malignant area .
- Impaired sensations .
- Anesthetic area .
- Advanced cardiac disease .
- Eczema .
- Dermatitis .
- Impaired circulation .
- Non-inflammatory edema .
- Altered consciousness .
- Hemorrhagic conditions.
- Varicose veins .
- patients who are in extremes of age and following X-ray therapy.
Physiological Effects of Infrared radiation .
When infrared rays are applied to the body, they are absorbed by it. As a result of absorption of infrared rays, the electromagnetic energy is converted into the thermal energy and thus heat is produced. The principle physiological effect of the infrared rays on the body is heat production. Other physiological effects occur as a result of heat production. Various physiological effects of infrared rays are
- Local rise in temperature .
- Increased activity of sweat glands .
- Increased metabolism .
- vasodilation and relaxation of muscle tissue.
On extensive or the general treatment of the entire body, there is general rise in body temperature and fall in blood pressure.
Therapeutic Effects of Infrared radiation .
1. In relieving pain .
Infrared radiations are effective in relieving pain. Mild heating on the superficial tissues by infrared radiations causes sedative effects on the superficial sensory nerve endings. Pain may be due to accumulation of waste products of metabolism, an increased flow of blood through the part removes these substances and thus relieves the pain.
The pain due to acute inflammation or recent injury is relieved most effectively by mild heating. When pain is due to chronic injury or inflammation, stronger heating is required. The treatment may last up to 30 minutes.
2. In muscle relaxation .
Relaxation of muscles is achieved by heating the tissues. Mild heating by infrared causes relaxation of muscles and thus relieves spasm. Relief of pain also induces relaxation in muscles and helps relieving muscle spasm associated with injury or inflammation. Relaxation of muscles provides greater range of motion to the exercising part as it relieves muscular spasm.
3. In increasing blood supply .
Infrared radiations increase the temperature in the superficial tissues, causing vasodilatation in the superficial tissues. It provides more white blood cells and fresh nutrients to the area being treated. It also accelerates removal of waste products and helps bring about resolution of inflammation.
It is most beneficial in the treatment of various arthritic conditions of joints which leads to inflammation and stiffness. Cases of post-immobilization stiffness, open wound and infections can also be effectively treated. Fresh supply of blood rejuvenates the tissues, removes waste products of metabolism and also relieves muscular spasm.
Dangers of Infrared Radiations .
1. Burn .
Excessive heating of superficial tissues causes burn. Sensation must be checked before starting the treatment. If sensation is not proper, the patient may not appreciate the extent of heating. The burn may be caused due to the following reasons:
- If intensity of radiation is too high .
- If sensation is not proper .
- Patient fails to report over heating .
- Unconscious patient .
- Patient moves closer to the lamp .
- Falls asleep during the treatment.
The patient must be warned to inform undue heating immediately. The spacing must be reduced gradually in order to increase the heating. Impaired blood flow through the part, which may be due to some circulatory defect or due tight garments reduces circulation and thus causes burn.
2. Electric shock .
Electric shock can occur if some exposed part of the circuit is touched by the patient. Due to heating of the wires in the circuit, insulation of wires may go off and thus regular checking of wires is necessary to avoid electric shock.
3. Faintness or giddiness .
Extensive irradiation may cause fall in blood pressure which may result in faintness or giddiness due to hypoxia of the brain. This is particularly common when the patient rises up suddenly from the recumbent position after extensive treatment.
4. Headache .
Irradiation of the back of the head may cause headache. Headache may also occur when treatment is given during hot weather. Lots of fluid goes off the body in the form of sweating during treatment. Plenty of water needs to be replenished during or after the treatment especially in hot weather.
5. Gangrene .
Gangrene may be caused in the areas of defective arterial blood supply following prolonged irradiation by infrared radiation. Arterial supply to the area being treated needs to be proper to avoid gangrene.
6. Injury to the eyes .
Direct heating over the eyes causes drying up and thus leads to corneal or retinal burns. Eyes needs to be protected following treatment to avoid injury.
