Light Modalities

Chapter 19

Description

• Light modalities are found on the electromagnetic spectrum– Most abundant form of energy in the universe

• Drying superficial tissues or via superficial photochemical effects

• Some mild superficial thermal effects

Types of Therapeutic Lamps

• Infrared– Superficial dry heat

• Ultraviolet– Heats the body’s tissues for either tissue

destruction or therapeutic effects

• Visible– Combination of ultraviolet and infrared known

as Lasers

Infrared Lamp• Used to dry seeping open wounds or sedate

superficial sensory nerves• Radiant modality: An electrical current passes

through a carbon or tungsten filament– Intensity controlled by adjusting current flow or

distance between lamp and tissue– Constant temperature, increased risk of burns– Heating skin depends on the amount of radiation

absorbed• Pigmented, darker skin will absorb more energy and will

heat more rapidly than lighter skin

Types of Infrared Lamps

• Near-Infrared– Luminous Infrared Lamp– Wavelength: 780 to 1,500 nm (closest to visible

light)– Thermal Effects: 5 to 10 mm deep– Energy formed by carbon and tungsten filament

• Light bulb

• Some energy is reflected by the surface of the skin

Types of Infrared Lamps

• Far-Infrared– Nonluminous Infrared Radiation– Wavelength: 1,500 to 12,500 nm– Thermal Effects: < 2mm

• Less penetrating than Near-Infrared – Skin feels warmer

– Energy formed by metal coil • i.e. electric stove or space heater• Invisible to human eye

Effects of Infrared Lamps

• Constant, dry heat to assist with superficial tissue– Dermatological conditions– Increase cell metabolism– Blood flow– Muscle Relaxation

• Contraindications– Any conditions in which other forms of

superficial heat are contraindicated

Clinical Applications

• Turn On and warm if necessary• Treatment Duration: 20 to 30 minutes• Intensity: adjust wattage or distance of lamp

– Luminous = 24 inches– NonLuminous = 32 inches– Inverse Square Law– Cosine Law

• Clean sweat and dirt, remove jewelry, and fit infrared goggles (if applicable) for patient

Ultraviolet Therapy

• Used to produce photochemical reactions in the skin

• Wavelength: 180 to 400 nm

• 3 UV bands (A, B, and C) produce unique effects

Types of UV

• UV-A– AKA: near UV– Effects: Erythema without pigmentation

• UV-B– AKA: middle UV– Effects: Erythema without pigmentation,

formation of vit D, skin tanning (blister/burn)

• UV-C– AKA: far UV– Kills bacteria, formation of vit D, skin tanning

Types of UV Lamps

• ‘Hot’ UV Lamps– Low Volt (30-110V) High-Amp (5A)– Electrical current passes through tube, argon

gas heats, vaporizing and polarizing mercury to produce UV light in ALL 3 bands and visible violet light

• ‘Cold’ UV Lamps– High Volt (3000V) Low-Amp (15mA)– Energy is cooler than ‘Hot’ and produce UV-C

Biophysical Effects

• Energy absorbed at a depth between 0.20 to 0.22 mm• Damages cell proteins, DNA, & RNA to initiate local

inflammatory responses• Effects:

– Vitamin D synthesis– Enhances melanin production– Thickens epidermis– Superficial vasodilatation– Bactericide

Effects of UV Lamps

• Wound Healing– Activates inflammatory response

– Use: Cold Lamps at intensity of E3

• Treat Skin Disorders– i.e. psoriasis– Exfoliates tissue and damage DNA that produces the

excess skin growth associated with psoriasis– Use: UV-B

UV Contraindications

• Sunlight sensitivity

• Fair skin (precaution)

• Medications or food that increase sunlight sensitivity

• Hyperthyroidism

UV Dosage

• Determined by Minimal Erythema Dose– Least amount of UV exposure time to produce

redness within 1-6 hrs and disappear within 24 hours

• ‘Hot’ Lamps– Determined by each patient and each lamp– Standard distance = 30 in., not closer than 15 in.

• ‘Cold’ Lamps– Standard MED value– 12-15 seconds at a distance = 1 in.

Determining MED for UV Lamp

• Cardboard Test Strips1. 6 different shapes cut out2. Use to cover shapes

• UV Lamp 30 in. away• Exposes 1 cut out, open the shutters for 30- sec.,

expose the 2nd cut out and leave the 1st uncover for the 30-sec.

• Repeat the steps above for the remaining 4 cut outs, but expose them at 15-sec intervals

• Instruct patient to check area every hour and record changes

UV Treatment Dosage• SED

– No erythema

• MED– Smallest dose that produces erythema within 1-6 hr

• E1

– Erythema lasts for 1-3 days, some scaling of skin present, approximately 2.5x MED

• E2

– Erythema with edema, peeling, and pigmentation, approximately 5x MED

• E3

– Severe erythema and burning, blistering, peeling, edema, approximately, 10x MED

Clinical Application

• Calculate treatment dose and duration• Clean area and remove jewelry• Cover skin not being treated (sunscreen if

applicable)• Fit UV-resistant goggles to patient and clinician• Position lamp at right angle using the correct

distance and duration for each type of lamp• Clean machine and check periodically for

maintenance of bulbs

Adjusting the Treatment Dose

• Biophysical changes occur with light exposure causing changes in treatment

• Duration– 30 to 50% increase for each subsequent treatment

– If 3 to 5 minutes, then distance is reduced

– 5 to 10 sec is decreased when missing a treatment

• Be aware of patients skin color and the lamps distance, duration, and angle

Therapeutic Lasers

• L=Light

• A=Amplification by

• S=Stimulated

• E=Emission of

• R=Radiation

• Classified by the FDA’s Center for Devices and Radiological Health

Types of Lasers• High-Power Laser

– “Hot Laser”– Effect:

• Causes thermal changes in tissues (cause tissues to be destroyed, evaporated, or dehydrated)

– Uses:• Surgery• Capsular shrinkage• Wrinkle and tattoo removal

• Low-Power Laser– “Cold Laser”– Effect

• Causes photochemical changes in tissue– Uses:

• Wound healing• Arthritis• Burn care

Production of Laser Energy

• Lasers are referred to by the type of active medium (gas, liquid, solid)– HeNe: visible red light penetrating 0.8 to 15mm– GaAs: invisible penetrating up to 2 cm

• Energy is introduced into the active medium

• An orbiting electron briefly elevates into a higher or ‘excited’ state

• The electron spontaneously returns and releases another photon

Effects of Lasers

• Photons are absorbed by tissues to alter molecular-level activity

• Theorized to affect pain-producing tissue (muscle spasm), by increasing ATP synthesis that increases cell metabolism and encourages the release of free radicals

Wound Healing

• Superficial wounds– Ulcers, surgical insicison, burns

• Lasers alter cell membrane permeability and increase in fibroblast, lymphocyte, and macrophage activity occurs

• Blood and lymph improve to promote the growth of granulation tissue

• Increase collagen and tensile strength of healing wounds

Pain Reduction

• Decrease acute and chronic pain

• Reduce the rate and velocity of sensory nerve impulses– Similar to cryotherapy but without thermal

changes

Fracture Healing

• May enhance fracture healing and bone remodeling by increasing capillary formation, calcium deposition, increase callus formation, and reducing hematomas

• Photons striking the tissue create acoustic waves that affect bone healing similar to ultrasonic bone growth stimulators

Clinical Application

• Because of the investigational status of therapeutic lasers, the clinical application is not described.