Ultraviolet rays definition .
Ultraviolet rays are invisible rays with wavelengths between 10 to 400 nm. Ultraviolet rays are of three types namely ultraviolet A, B and C. Although, ultraviolet rays are emitted by the sun, for physiotherapeutic treatment ultraviolet generators produce them. Most of these generators produce ultraviolet rays from mercury. Various generators such as high-pressure mercury vapor lamp, low-pressure mercury vapor lamp, fluorescent tubes, Kromayer lamp, PUVA box, theraktin tunnel, etc. can be used for physiotherapeutic applications.
Ultraviolet radiations are invisible to the human eye. Ultraviolet radiations can cause sunburn and tanning on exposure to the sunlight. Ultraviolet radiations transmit much more energy than the visible radiations. For descriptive purposes, the therapeutic part of the ultraviolet spectrum may be divided into:
- UVA: Wavelength 315–400 nm .
- UVB: Wavelength 280–315 nm .
- UVC: Wavelength below 280 nm .
Production of Ultraviolet Radiations .
Although ultraviolet rays are emitted by the sun but for therapeutic purposes, some form of generator is used. Most of these generators produce ultraviolet rays from mercury. Various types of generators are used such as high pressure mercury vapor lamp, Kromayer’s lamp, fluorescent tubes, theraktin tunnel, PUVA apparatus, etc. for the production of ultraviolet rays.
1. High Pressure Mercury Vapor Lamp .
It consists of a U-shaped glass tube, filled with argon gas at a low pressure. Small amount of mercury is enclosed in the tube and the tube is sealed at both the ends . U-shaped glass tube is used so as to act as a point source. The burner is made up of quartz as this material allows the passage of ultraviolet rays and can withstand very high temperatures with low coefficient of expansion. At the ends of the glass tube, electrodes are placed, enclosed in metal caps across which a high potential difference is applied.
Step-up transformer is used to apply high potential difference, i.e. 400 volts across the two metal caps surrounding ends of tube to ionize the argon gas. Once the argon has been ionized, normal mains voltage between the electrodes causes the positive and negative particles to move through burner, constituting an electric current. The electrons move toward the positive terminal and positive ions move toward the negative terminal, collision between moving ions and neutral argon atom causes further ionization and a glow of discharge is produced. Also, sufficient heat is produced to vaporize the liquid mercury inside the tube and further ionization of mercury.
Thus, ultraviolet rays are produced by the process of argon ionization, mercury vaporization and mercury ionization which takes about 5 minutes to reach its peak. When the lamp is turned off, the ions of argon and mercury recombine so that within the tube everything returns to its neutral state. The tridymite formation: Some of the quartz changes to one another form of silica called tridymite due to very high temperature in the burner.
It is harmful to the total output of ultraviolet rays as it is opaque to the rays and total output of the lamp gradually decreases as the proportion of tridymite increases at around 1000 hours of ultraviolet rays production that much tridymite can form that the whole burner tube needs to be replaced. A variable resistance is included in the burner circuit as a method of compensation and resistance is reduced in order to increase the current intensity so as to produce adequate ultraviolet rays.
2. The Kromayer’s Lamp .
It has advantage over high-pressure mercury lamp that it can be used in contact with the body tissues as the harmful infrared rays are absorbed by the circulating water so there is no danger of burns.
Construction of Kromayer’s Lamp .
The Kromayer’s lamp is a water-cooled mercury vapor lamp which eliminates the danger of burn and absorbs infrared rays. The high pressure mercury vapor lamp is surrounded by circulating distilled water so as to absorb infrared rays . Kromayer’s lamp can also be used to treat sinuses or deep body cavities. Direct contact method can also be used as it minimizes the danger of burn.
3. Fluorescent Tubes .
Mercury vapor lamp has disadvantage that it produces a certain proportion of short ultraviolet rays. Modern treatment methods often require the use of long waves ultraviolet rays only without having short waves. In order to achieve this, fluorescent tubes are used. Each tube is about 120 cm long and is made up of a glass which allows long ultraviolet rays to pass. The inside of tube is coated with special phosphor. The spectrum of each tube depends upon the type of phosphor coating. A low pressure arc is set up inside the tube by the process of ionization. Phosphor is used to absorb short wave ultraviolet rays and these are reemitted at longer wavelengths. Accurate control of emitted wavelength is possible depending upon the type of phosphor used.
4. Theraktin Tunnel .
The Theraktin tunnel is a semi-cylindricular framework in which four fluorescent tubes are mounted in its own reflector in such a way that an even irradiation of a patient is achieved . Normally, fluorescent tubes with a spectrum of 280–400 nm are used.
5. PUVA Apparatus .
Irradiation with UVA only, may be performed with special fluorescent tubes which may be mounted in a vertical battery on a wall or on four sides of a box totally surrounding the patient. This form of ultraviolet rays are usually given for two hours after the patient has taken a photoactive drug such as Psoralen, hence the term PUVA (Psoralen-Ultraviolet-A) is used.
Techniques of Application .
1. Test dose .
Individual patient’s reaction to the ultraviolet radiations is used to assess the test dose. The technique of administering the test dose is very similar whether the Kromayer’s lamp, fluorescent tube or theraktin tunnel is used. The only difference is of distance and timings.
2. Calculation of test dose by air-cooled lamp:
A suitable area of skin such as flexor aspect of forearm is used for calculation of test dose. The skin is washed to remove any dust or grease. Three differently shaped holes are cut with a material which is resistant to the passage of ultraviolet rays such as card board, paper or lint. The size of the middle hole is about 2 cm × 2 cm with the hole on one side larger and on the other side smaller. A number of people are tested to find out average E1 time and distance by seeing a erythema reaction. By knowing the average E1 (time and distance) for a particular lamp,
the duration of E2, E3 and E4 doses can be calculated.
- E2 time = E1 time × 2½ .
- E3 time = E1 time × 5 .
- E4 time = E1 time × 10 .
Also, by inverse square law half the distance requires quarter the time for having the same effect. The cut out test paper or lint is applied to the patient’s forearm and the body is screened. The middle hole receives the calculated E2 dose. The small hole receives an exposure slightly longer than E2 and the larger hole receives an exposure slightly shorter. The procedure is carefully recorded on the patient’s treatment card and all the three holes are given to the patient to record when the erythema appears, how severe it is and how long it lasts. The patient’s reaction will determine further dosages.
3. Calculation of test dose by Theraktin tunnel .
Same procedure is used to calculate the test dose as discussed above, however larger holes of about 4 cm × 4 cm are used and are placed on the abdomen. The rest of the body is screened.
4. Calculation of test dose by Kromayer’s lamp .
Since the Kromayer’s lamp is used in contact with the skin, the test dose is calculated by using very small holes, i.e. 0.25 cm × 0.25 cm and the exposure time needs to be very short. Ultraviolet radiations can cause severe damage to the skin; the only indication seen is the erythema reaction on the skin. The E1 dosage needs to be carefully recorded and clearly marked on the treatment lamps.
Techniques of General Irradiation .
- The patient’s body part is washed to remove any dust or grease by soap and soaked with a towel to remove any moisture.
- The patient is explained about what is going on and how it will occur.
- The patient is positioned in comfortable posture so as to allow the maximum exposure of the part being treated and to avoid undue exposure of other parts.
- A thin film of petroleum jelly (an effective screening agent) is used for soft structures like lips, ear lobes, eyelids, nipples, navel, etc. A thick blanket is used to cover rest of the body which does not need exposure. Eyes need to be protected by cotton wool or goggles to avoid exposure.
Indications of Ultraviolet Irradiations .
1. Wounds .
The ultraviolet radiations are used for the treatment of infected and noninfected wounds. For infected wounds, the effects of ultraviolet radiations are to destroy bacteria, to remove infected dead material, to promote repair and to increase healing. UVB rays are generally used by using Kromayer’s lamp with E3 or E4 doses. For noninfected wounds, the effects of ultraviolet radiations are to stimulate the growth of granulation tissue and to promote repair and to increase healing. UVA rays are generally used by using some filter such as cellophane, etc.
2. Acne vulgaris .
Acne is a chronic inflammatory condition of the skin which presents with pustules, papules and comedones. It blocks the hair follicles and sebaceous glands on the face, back and chest. An E2 dose of ultraviolet radiation may be given with the following aims: An erythema will bring more blood to the skin and so improves the condition of the skin. Desquamation will remove comedones and allow free drainage of sebum, thus reducing the number of lesions. Also, it have a sterilizing effect on the skin.
The intensity of dose needed, i.e. E2 + is often painful and cosmetically not acceptable to the patient. Treatment is only palliative and the condition usually returns within a few weeks of UVR. Unfortunately, it may even appear to be worse a few weeks after UVR, as all the lesions in the skin reach their peak at the same time, whereas in the normal course of acne some will be resolving and others develop. Irregular rates of desquamation may restrict the frequency of treatment and possibly produce a mottled erythema.
3. Pressure sores .
Ultraviolet radiations are used for the treatment of pressure sores. Pressure sores occurs due to any pressure injury which may vary from an area of erythema to a deep seated ulcer exposing the underlying bone. Ultraviolet rays are used to treat the pressure sores as described in wounds.
4. Psoriasis .
Psoriasis is a skin condition in which there are localized patches on the skin. It affects about 2% of population and the cause is unknown but thought to be inherited. Formation of thick pink or red plaques sharply demarcated and covered with silver scales are common features. The aim of the UVR treatment is to decrease the proliferation by reducing the DNA synthesis. Treatment is given by using the Goeckerman regimen, Leeds regimen or PUVA.
Goeckerman regimen .
This consists of coal tar application 2–3 times a day with general (total body) UVB radiation given once a day as a subthermal or E1 dose.
Leeds or Ingram regimen .
In this the sensitivity of the patient’s skin is increased by the local application of coal tar, added to the bath prior to the treatment. The psoriatic lesions are covered with dithranol cream, which inhibits DNA synthesis. Next day the dithranol is cleaned off, and the process is repeated. A suberythemal dose E1 is given to the patient, using a Theraktin tunnel or a aircooled lamp at 100 cm. The dose is repeated daily and is increased daily at a rate of 12.5%.
PUVA .
Psoriasis is treated with ultraviolet radiations along with a sensitizer. Sensitizing drug psoralen is given two hours before the exposure of UVA rays. This inhibits the DNA synthesis and thus cell replication. Dosage of PUVA regimen needs to be measured regularly. Dosage depends upon the patients skin type. Using psoralen along with ultraviolet rays gives its name PUVA (psoralen ultraviolet A). Long-term use can lead to skin damage and increases the risk of squamous cell carcinoma.
5. Alopecia .
Alopecia is premature falling of hairs leading to baldness. Alopecia is a relatively common condition in which hairs falls out in patches. Suberythemal doses For noninfected wounds, the effects of ultraviolet radiations are to stimulate the growth of granulation tissue and to promote repair and to increase healing. UVA rays are generally used by using some filter such as cellophane, etc.
6. Rickets .
When ultraviolet rays are absorbed in the skin, it converts 7-dehydrocholesterol into vitamin D. Vitamin D is necessary for the absorption of calcium and is essential for the formation of bones and teeth. It helps reducing osteoporosis and thus reducing fractures. It is beneficial in be-ridden, elderly patients or chronic debilitating patients where chance of osteoporosis is more.
7. Counter-irritation effect .
Ultraviolet rays are used to produce strong counter-irritation effects over the site of deep rooted pain. An E3 or E4 dose is given to the area and is then covered with dry dressing. Superficial pain produced by the erythema, mask the deeper pain and also the modern pain gate theory also justifies this.
8. Psychological effects .
UVR therapy also gives the patient a sense of general well-being .
Contraindications .
1. Acute skin conditions .
Certain skin conditions like acute eczema, dermatitis, lupus erythematosus, or herpes simplex must be avoided irradiation.
2. Hypersensitivity to sunlight .
Certain patients those who are hypersensitive to the sunlight are also avoided irradiation.
3. Deep X-ray or cobalt therapy .
Patients those who have taken deep X-ray or cobalt therapy can have devitalization of the tissues. Hypersensitivity of the skin can occur.
4. Skin grafting .
Recent cases of skin grafting should not be given UVR.
Dangers of ultraviolet Radiations .
1. Eyes .
Eyes of the patient or the physiotherapist needs to be protected by goggles from ultraviolet radiations otherwise there is a danger of conjunctivitis formation or cataract to occur. UVB and UVC are absorbed by the cornea, but UVA is absorbed by the lens and is implicated in the formation of cataract. Thus, wearing suitable goggle is necessary from preventing any injury to the eyes.
2. Overdose .
There are a number of factors due to which the patient can receive overdose during treatment.
- Too long the exposure: The duration of exposure needs to be accurate. A proper timer with suitable audible sound and auto-cut device should be used.
- Moving the lamp closure to the patient: This leads to exposure of larger doses to the patient. Patient needs to be instructed not to move during treatment. Therapist himself must calculate the distance by the application of inverse-square law.
- Changing the lamp: It can also lead to overdose. Average E1 must be carefully recorded and marked on every lamp. Care must be taken while using any new lamp.
- Use of sensitizers: Sensitizers must be administered and used carefully to avoid any harmful effect.
Physiological Effects of Ultraviolet Radiations .
Ultraviolet rays are absorbed by the skin which acts as protective layer. UVB and UVC are absorbed by the epidermis whereas UVA may penetrate as far as capillary loops in the dermis. The skin protects the underlined cells and intracellular structures from most ultraviolet rays because the energy these rays release is sufficient to cause damage to the cells and the intracellular structures.
1. Carcinogenesis.
Sun can be called as a universal carcinogen. Prolonged exposure of UVB or UVC can lead to carcinogenesis as these rays may affect DNA and thus cell replication. The extent of carcinogenesis depends upon the wavelength of the ultraviolet radiations and amount of ultraviolet rays absorbed. So, prolonged exposure of patient’s skin to ultraviolet rays should be avoided and the course of treatment should not exceed beyond four weeks.
2. Erythema .
Damage to cells causes release of histamine like substance from the epidermis and the superficial dermis. A gradual diffusion of this chemical takes place until sufficient chemical has accumulated around the blood vessels in the skin to make them dilate. The greater the quantity of histamine like substance, the sooner and fiercer is the reaction. The erythema reaction is used to classify doses of ultraviolet rays given to the patients. The erythema is produced by wavelengths shorter than 315 nm.
3. Pigmentation .
Pigmentation develops within two days of irradiation. Ultraviolet rays stimulate melanocytes in the skin so as to produce melanin. The melanin covers the nucleus of the cell to protect it from ultraviolet rays and forms an umbrella over the nucleus of the cell. Pigmentation substantially reduces the penetration of UVB. The extent of pigmentation varies from individual-to-individual and it is more in the dark skin than in the fair skin.
4. Thickening of the epidermis .
Sudden over-activity of the basal layer of the epidermis causes a marked thickening, particularly of the stratum corneum (the outermost layer). The thickening may occur to the extent that as much as three times its normal thickness. The therapeutic doses may required to increase until desquamation has not taken place.
5. Desquamation .
The increased thickness of the epidermis is eventually lost by the process of desquamation or peeling. When desquamation has taken place, the resistance of the skin to the ultraviolet rays is substantially reduced.
6. Production of vitamin D .
Vitamin D is necessary for the absorption of calcium and is essential for the formation of bones and teeth. When ultraviolet rays are absorbed in the skin, it converts 7-dehydrocholesterol into vitamin D. It helps reducing osteoporosis and thus reducing fractures.
7. Effects on eyes .
Strong doses of ultraviolet rays to the eyes can lead to irritation and watering. Strong doses of UVB and UVC to the eyes can lead to conjunctivitis or slow blindness.
8. Aging .
The normal process of aging is accelerated if there is continuous exposure to the ultraviolet rays. There is thinness of epidermis, loss of epidermal ridges, dryness, loss of melanocytes and wrinkling due to lack of dermal connective tissue. Fair skin races are at more danger than others. Persons taking sun-bath regularly should be aware of harmful effects of ultraviolet rays.
9. Antibiotic effect .
The increased body resistance to infection as a result of ultraviolet rays are due to its action on reticuloendothelial system. Short ultraviolet rays can destroy bacteria and some other small organisms such as fungi commonly found in wounds. E4 dose effectively destroys such microorganisms.
Therapeutic Effects of Ultraviolet Rays .
Various therapeutic effects of ultraviolet rays are counter-irritation, increased blood supply, destruction of bacteria, tissue destruction and desquamation.
1. Counter-irritation .
Ultraviolet irradiation may cause irritation of superficial sensory nerve endings and hence, may relieve pain through counterirritation. Usually, a third degree erythema dose is required for this purpose.
2. Increased Blood Supply .
Ultraviolet rays increase blood supply to the skin as a result of erythema reaction. It can be used in the treatment of certain conditions such as psoriasis, acne, alopecia and chilblains.
3. Destruction of Bacteria .
Ultraviolet rays can destroy bacteria. Hence, ultraviolet irradiation can be used in the treatment of superficial bacterial infections such as infected wounds, adenitis and acne.
4. Tissue Destruction .
Ultraviolet rays damage and destroy superficial cells. It may be applied to sluggish wounds for this purpose.
5. Desquamation .
This casting off reaction of ultraviolet rays is of value in the treatment of acne.
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