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Ultraviolet Therapy Ultraviolet Radiation (UVR) • In electromagnetic spectrum UVR ranges from 2000 to 4000 Å • Divided into three ranges: – UV-A- near UV- 3200 to 4000 Å • Little or no physiologic effect – UV-B- middle UV- 2900 to 3200 Å • Associated with sunburn and age-related skin changes – UV-C- far UV- 2000 to 2900 Å • Bactericidal Ultraviolet Radiation • UVR apparatus most likely to be used would generate UVR in UV-B, UV-C or both ranges • UVR is absorbed within first 1 to 2 mm of human skin • Most of physiologic effects are superficial • Used to treat various skin disorders Effect On Cells • Exposure of skin to UVR causes chemical excitation of cells which leads to physiologic changes within these cells • Alteration of cell biochemistry and cellular metabolism which affects synthesis of DNA and RNA • This leads to alterations in protein and enzyme production Short-Term Effects on Skin • Skin consists of two layers – Epidermis • Contains keratinocytes which produce keratin,fibrous protective protein of skin – Dermis • Papillary layer - rich blood supply • Reticular layer - heavy connective tissue containing fibroblasts, histocytes, and mast cells Erythema • Generalized response to UVR exposure culminates in development of an acute inflammatory reaction • End results of active inflammation are – Erythema - reddening of skin associated with sunburn – Pigmentation -tanning – Increased epidermal thickness Inflammation • Inflammatory response characterized by local vasodilation and increased capillary permeability causing erythema • Permits certain proteins to move from capillaries into dermis resulting in a change in osmotic pressure • Water drawn into area and edema occurs • Phagocytic cells eliminate dead cells Photosensitization • Over sensitization to UVR as a result of excitation of a chemical by UVR exposure • Acute effects of UVR exposure can be exacerbated if certain chemicals or medications are present on skin or in body Tanning • Increase of pigmentation in skin • Protective mechanism activated by UVR exposure • Increase of melanin (pigment responsible for darkening) within skin causes tan – Functions as a biologic filter of UVR • By scattering radiation • By absorbing UVR • By dissipating absorbed energy as heat Tanning • Immediate tanning occurs following UVR exposure – Appears most often in darkly pigmented individuals – Represents the darkening of melanosomes already present in the skin – Begins to fade 1 hour after exposure and is hardly noticeable 3 to 8 hours Tanning • Delayed tanning results from formation of new pigment (melanin) through melanogenesis – Delayed tanning usually becomes apparent 72 hours after UVR exposure Artificial Tanning Devices • Manufacturers claim tanning beds produce only UVR in UV-A spectrum and are safe – Production of this type of UV-A generator is largely unregulated – Effects of long-term exposure to UV-A are unknown – Caution should be exercised before using an artificial source to expose to UVR Long-Term Effects on Skin • Premature aging of the skin – Dryness, cracking, and a decrease in elasticity of skin resulting from epidermal solar elastosis • Alteration in the skin's elastic fibers • Linked to UVR-induced DNA damage Long-Term Effects on Skin • Skin cancer – Most common malignant tumor found in humans – Damage to DNA suspected as cause – Major types of skin cancer • Basal cell carcinoma( rarely metastasizes) • Squamous cell carcinoma (metastasizes in 5%) • Malignant melanoma (Usually metastasizes – Rate of cure exceeds 95% with early detection Sunscreens • Sunscreen’s effectiveness in absorbing sunburn inducing radiation is expressed as sun protection factor (SPF) • SPF of 6 indicates you can be exposed to UVR six times longer than without a sunscreen before receiving a minimal erythemal dose Effect On Eyes • UVR exposure of the eyes causes an acute inflammation called photokeratitis – Delayed reaction occurring within 6 to 24 hours – Conjunctivitis develops, accompanied by erythema of adjacent facial skin – Sensation of a foreign body on eye – Photophobia – Increased tear production – Spasm of the ocular muscles Systemic Effects • Photosynthesis of vitamin D following irradiation of skin by UVR in UV-B range – UVR can be used as treatment for disorders of calcium and phosphorus metabolism, such as rickets and tetany – Treatment of choice for such problems is dietary supplementation Ultraviolet Generators • • • • Carbon arc lamp Xenon compact arc lamp Fluorescent ultraviolet lamp (blacklight) Mercury arc lamp Carbon Arc Lamp • Composed of two carbon electrodes • Two electrodes move slightly apart causing current to arc across small gap • UVR is emitted between 3500 and 4000 Å • Electrodes gradually burn and must be replaced – Burning is noisy and causes an unpleasant odor Xenon Compact Arc Lamp • Composed of compressed xenon gas enclosed in a vessel • Electric arc passed through gas • Gas is heated to 6000° C • Emits infrared, visible, and UVR in range of 3200 to 4000 Å Fluorescent UV Lamp (Blacklight) • Low-pressure mercury lamp • Tube of UV-transmitting glass coated with phosphors • Phosphors are fluorescing substances that absorb the UVR and then reemit it at a longer wavelength • UVR emitted ranges from 3000 to 4000 Å Mercury Arc Lamp • Most likely kind of UVR lamp to be used • Either low-pressure or high-pressure mercury arcs – Mercury contained in a quartz envelope – An electric arc passes through vaporizing mercury – At 8000° C atoms become incandescent and emit ultraviolet, infrared, and visible light Mercury Arc Lamp • High-pressure = Hot Quartz • Most of UVR produced falls within UV-B range • Mainly used to produce erythema and accompanying photochemical reactions Mercury Arc Lamp • Low-pressure = Cold quartz lamp – Temperature of the quartz envelope is about 60° C – UVR spectrum limited to 1849 Å and 2537 Å – Does not require a warm up or cool down period, and is used mainly where bactericidal effect of UVR is desired Techniques of Application • Effectiveness of lamp assessed by determining skin sensitivity to UVR – Measured by the minimal erythemal dose (MED) • Exposure time needed to produce a faint erythema of the skin 24 hours after exposure • Question patient regarding photosensitizing drugs – Area of skin to be tested should have Measuring MED • Patient is draped except for test site • Piece of paper with five cutouts 1” square and 1”apart placed over the test site • Height of lamp from patient adjusted to same level as for treatment • Shutters are opened and cutouts exposed at 15-sec intervals 15, 30 , 45, 60, and 75 secs. Determining MED Patient returns in 24 hours and a visual inspection determines MED • Areas tested that reveal no erythema 24 hours after testing have received a suberythemal dose • Areas showing erythema at 24 hours have received a minimal erythemal dose. • Erythema still present at 48 hours = 1st degree erythemal dose • Erythema persists from 48-72 hours = 2nd degree erythemal dose • Erythema lasts past 72 hours= 3rd degree erythemal dose Determining MED • 1st-degree and 2nd-degree doses can be estimated – 1st-degree erythemal doses approximately correspond to 2.5 times minimal erythemal dose – 2nd-degree doses correspond to 5 times minimal erythemal dose Determining MED • Since human skin adapts to UVR exposure, MED will gradually increase with repeated treatments • Necessary to gradually increase exposure time to achieve the same reaction • Once determined it is increased 5 seconds per treatment • Height of lamp remains constant Positioning The Lamp • Apply cosine law and inverse square law • Distance of lamp must be kept constant if intensity of treatments is to be equal • Generally standardized at each clinic usually ranging from 24 to 40 inches Treatment Technique • Patient should be draped and wear eye goggles • Consistency in positioning of lamp is critical – Must be the same as in MED test • Clinician must also wear goggles • Open lamp shutters and begin timing simultaneously Clinical Applications • Most common use of UVR is in treatment of dermatologic conditions such as psoriasis and acne and hard to cure infectious skin conditions such as pressure sores • Development of oral and topical medications has greatly reduced the use of ultraviolet Indications for Ultraviolet Therapy • • • • • • • • Acne Aseptic wounds Folliculitis Pityriasis rosea Tinea capitum Septic wounds Sinusitis Psoriasis • Pressure sores • Osteomalacia • Diagnosis of skin disorders • Increased vitamin D production • Sterilization • Tanning • Hyperplasia Contraindications for Ultraviolet Therapy • Porphyrias • Pellagra • Lupus erythematosus • Sarcoidosis • Xeroderma pigmentosum • Acute psoriasis • Acute eczema • Herpes simplex • Renal and hepatic insufficiencies • Diabetes • Hyperthyroidism • Generalized dermatitis • Advanced arteriosclerosis • Active and progressive pulmonary tuberculosis