The paraffin wax has a low melting point and is contained in a bath thermostatically controlled between 40°C. Owing to its low thermal conductivity, wax heats more slowly but retains its heat for a longer period than water. As the paraffin wax solidifies on the skin the energy released by the latent heat for a longer period than water. As the paraffin wax solidifies on the skin the energy released by the latent heat of fusion results in heating of the tissues.
The advantages of paraffin wax are that it completely surrounds the part being treated and the patient does not need to remain in a fixed position. Also it is applied at a known temperature and gets cooler–therefore there is very little danger of a burn. Its disadvantages are that regular cleaning is necessary and it is difficult to apply except to the extremities. Its main use therefore is in treating hands and feet. Paraffin Wax is used to relieve pain after trauma, in degenerative joint disease and in the chronic stage of inflammatory arthropathies. Skin condition can be improved following the removal of plaster of Paris. Adhesions and scars can be softened and mobilization is facilitated. It should not, however, be applied over open wounds or skin infections.
Laser The word laser is an acronym for Light Amplification by Stimulated Emission of Radiation. It obeys the laws of radiation. Specific substances are stimulated laser rays electrically to emit radiations which produce greater energy levels. The helium/neon mixture produces a red light and the infra–red produces no light. The probe may produce a single wavelength or a cluster of wavelengths. Laser is different from other forms of light because it is monochromatic (one wavelength only), the beam of light being narrow, parallel and uniform. The laser waves are identical, superimposing on each other and therefore giving an amplifying effect.
There are three types of lasers:
- Power laser used in surgery for destructive effect.
- Soft laser (helium/neon) used for superficial lesions of the skin.
- Mid–laser (gallium, aluminum, arsenide). The wavelength produced depends on the ratio of each material. These are most commonly used because of their depth of penetration (30–40nm).
- Increases collagen synthesis–useful for tissue repair.
- Increases permeability of cell membranes with increased efficiency of sodium.
- Increases number of fibroblasts and promotes granulation tissue–useful for wound healing.
- Increases levels of prostaglandin. Causes an increase in cellular ATP, which is useful for pain relief.
- Open wounds–ulcers, postoperative wounds.
- Skin conditions–psoriasis, burns.
- Soft–tissue injuries–tendons, ligaments and muscles.
- Degenerative and inflammatory arthropathies.
- Pain relief over trigger or acupuncture points.
- Skin irritation.
- Chest treatment in cardiac patients should be avoided, together with those who have a pacemaker.
- The eyes.
These are plastic–covered pads similar to but smaller than electric blankets. A pad has three levels of heat and is useful for treating the neck or back. The patient lies on it and heat passes to the tissues by conduction. An advantage is that the heat can be applied at the same time as traction.
Hot moist packs
These are canvas bags filled with a hydrophilic substance and stored in a thermostatically–controlled cabinet of water between 75°C and 80°C. The packs vary in size and shape and are returned to the cabinet for reheating after use. The area to be treated should be totally covered by the pack, which is molded to the contour of the body. Layers of toweling must be placed round the pack to separate if from the patient’s skin. The superficial tissues are heated by conduction, relieving pain and muscle spasm. Moist heat is conducted more uniformly than dry heat. These packs are particularly useful on uneven surfaces because they can be easily molded to the surface, but they are heavy and may cause discomfort.
Ultraviolet Rays (UVR)
These are electromagnetic rays between the visible rays and X–rays in the electromagnetic spectrum (400–100nm).
The ultraviolet rays are produced ultraviolet by vaporization of mercury in a quartz tube. All ultraviolet burners produce visible and infra–red–rays. For therapeutic sources of Ultraviolet Rays. In the Kromayer lamp water absorbs the infra–red rays and allows treatment in contact with the patient’s skin. With the air–cooled source the patient is treated at a distance of 45 cm or more to avoid burning of the skin from the infra–red rays.
Laws of radiations
A larger area is irradiated but the intensity is decreased when the distance from the source to the patient’s skin is increased. Ultraviolet Rays are governed by the law of inverse squares which states that the intensity of rays falling on a plane surface varies inversely with the square of the distance from the point source. To irradiate a smaller area the source is moved nearer to the patient but the time of exposure must be altered to maintain the same intensity in accordance with the law of inverse squares.
Ultraviolet Rays must strike the surface at 90° to the erythema reaction after an E1 has been determined from a skin test.
The other erythema dosages can be calculated as follows:
- Suberythema 75% of E1.
- E2 = 2.5 x E1.
- E3 = 5 x E1.
- E4 = 10 x E1.
- Double E4 = 20 x E1.
- E4 + Double E4 are used on open wounds.
When Ultraviolet Rays is applied to normal skin there is thickening of the epidermis therefore progression of dosage is necessary to obtain the same effective level.
Doses can be progressed as follows:
- Suberythema–previous dose plus 12.5%.
- E1–previous dose plus 25%.
- E2–previous dose plus 50%.
- E4–previous dose plus 75%.
Contraindications to Ultraviolet Rays
- Deep X–ray therapy during the preceding 3 months because the skin may be hypersensitive to UVR.
- Tuberculosis or malignant disease may be exacerbated by UVR.
- Hypersensitivity to sunlight–patients who react adversely to the sun should not be treated with Ultraviolet Rays
- Dermatological conditions such as acute eczema, lupus erythematosis may be exacerbated by UVR.
- After infra–red therapy–UVR given whilst the erythema from the infra–red is still present may result in increased effects.
- Pyrexia–Ultraviolet Rays may produce a further increase in temperature.