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Infrared Radiation (IRR) - Physiotherapy Modality

Definition

• Wavelength range: 760 nm to 1 mm
• It lies just beyond the red end of the visible spectrum

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Classification

By Wavelength (Current WHO Classification)

Former/Traditional Classification

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Sources of IRR

Natural Source

• Sun (primary natural source)

Artificial Sources (used in physiotherapy)

1. Non-Luminous (Non-Radiant) Generator

• Produces long/far infrared rays (1500+ nm)
• Heat source: coiled resistance wire heats a fireclay element to ~500°C
• The element itself emits rays (no glow visible)
• Needs warm-up time (~15 minutes)
• Produces predominantly IRC/IRB waves
• Suitable for: acute inflammatory conditions (sedative/soothing effect)
• Distance: 45-60 cm from skin

2. Luminous (Radiant) Generator

• Produces short/near infrared rays (760-1500 nm)
• Source: tungsten filament lamp (similar to incandescent bulb)
• Emits a visible red glow along with IRR
• No warm-up time required
• Penetrates deeper into tissues
• Suitable for: chronic conditions (deeper heating effect)
• Distance: 45-75 cm from skin

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Physical Properties / Penetration

• IRR is largely absorbed in the superficial layers of skin
• Effective penetration depth: 2 to 7 cm (claimed by some sources; most heating occurs in top few mm)
• Shorter wavelengths (near IR) penetrate deeper than longer wavelengths
• Absorbed by photoreceptors in cells, triggering metabolic processes
• Nitric oxide release is considered a key mechanism of action

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Physiological Effects

1. Vasodilation - increased blood flow (hyperemia) in superficial tissues
2. Increased metabolism - raised local tissue temperature increases metabolic rate
3. Muscle relaxation - relief of muscle spasm due to heat
4. Pain relief (analgesia) - stimulation of sensory receptors, counter-irritation
5. Increased tissue extensibility - useful before stretching
6. Accelerated healing - increased circulation promotes tissue repair
7. Sedative effect - particularly with non-luminous (long wave) sources
8. Reduction of inflammation - particularly in subacute/chronic phases

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Therapeutic Indications

• Arthritis (osteoarthritis, rheumatoid arthritis - chronic phase)
• Bursitis and tendonitis
• Back pain and neck pain
• Muscle spasm and stiffness
• Blunt trauma (subacute/chronic stage)
• Carpal tunnel syndrome
• Sciatica
• TMJ (temporomandibular joint) pain
• Diabetic neuropathy
• Wound healing and tissue repair
• Neonatal care (in NICU)

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Contraindications

• Acute inflammatory conditions (heat worsens acute inflammation)
• Impaired/absent skin sensation (risk of burns)
• Malignancy in the treatment area
• Active bleeding or recent hemorrhage
• Impaired circulation (arterial disease)
• Pregnancy (especially over the abdomen/pelvis)
• Metal implants in the treatment area
• Open wounds / skin infections
• Photosensitive patients (those on lithium, melatonin, certain antibiotics)
• Patients with hip or knee replacements
• Unreliable/confused patients (cannot report pain accurately)

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Precautions

• Always perform a skin sensation test before treatment
• Patient must be able to communicate during treatment
• Avoid direct eye exposure (use goggles if treating near the face)
• Never allow patient to touch the lamp
• Check the skin every few minutes during treatment
• Remove jewellery and metal objects from the area

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Dosage and Technique

• Inverse Square Law: Intensity is inversely proportional to the square of the distance (I ∝ 1/d²)
• Cosine Law (Lambert's Law): Maximum absorption when rays strike the surface at 90°
• Grotthus-Draper Law: Only absorbed rays produce a physiological effect

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Comparison: Luminous vs Non-Luminous

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Summary for Exam

• IRR is a superficial thermotherapy modality
• Two types: luminous (short wave, deeper, no warm-up) and non-luminous (long wave, superficial, needs warm-up)
• Main effects: vasodilation, analgesia, muscle relaxation
• Key contraindication: impaired sensation (burn risk)
• Always apply perpendicular at the correct distance
• Duration: 10-20 minutes; session governed by inverse square and cosine laws

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Ultraviolet Radiation (UVR) - Physiotherapy Modality

Definition

• Wavelength: 100 nm to 400 nm
• Not visible to the naked eye
• Classified and standardised by the CIE (Commission Internationale de l'Eclairage)

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Classification (Types)

UVC is filtered by the ozone layer and does not reach Earth naturally. UVA and UVB reach the Earth from the sun.

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Sources of UVR

Natural Source

• Sun (emits UVA + UVB; UVC filtered by ozone)

Artificial Sources (used in physiotherapy)

1. Mercury Vapour Lamp (Hot Quartz Lamp)

• Low pressure or high pressure mercury vapour
• Emits predominantly UVB and UVC
• Used for general (whole body) irradiation
• Needs 5-10 min warm-up time
• E.g., Hanovia lamp, Alpine Sun lamp

2. Kromayer Lamp (Cold Quartz Lamp)

• High pressure mercury vapour in a water-cooled quartz burner
• Emits UVC predominantly
• Used for local treatment of skin conditions, wounds
• Can be used with contact technique (pressed directly to skin)
• Water cooling allows close application without burning

3. Fluorescent Lamps / Solaria

• Used for PUVA therapy (Psoralen + UVA)
• Emit predominantly UVA
• Used in dermatology departments

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Physical Laws Governing UVR

1. Inverse Square Law: Intensity inversely proportional to the square of distance (I ∝ 1/d²)
2. Cosine Law (Lambert's Law): Maximum intensity when rays are perpendicular to the surface
3. Grotthus-Draper Law: Only absorbed rays produce a biological effect
4. Bunsen-Roscoe Law (Reciprocity Law): Biological effect = Intensity × Time (can vary time or distance to achieve same dose)

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Minimal Erythema Dose (MED) - Test Dose

How to Determine MED (Test Dose Procedure)

1. Expose a small area of skin (inner forearm) using a card with 3 holes
2. Give 3 exposures: 30 seconds, 60 seconds, 90 seconds (at standard distance, usually 50 cm)
3. Check the skin at 6-8 hours and again at 24 hours
4. The shortest exposure producing erythema still visible at 24 h = E1 (MED)

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Erythemal Doses

Progression of Doses

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Physiological Effects

Immediate Effects

1. Erythema - vasodilation due to histamine and prostaglandin release
2. Pigmentation (tanning) - stimulation of melanocytes (UVA > UVB)
3. Skin thickening - hyperplasia of stratum corneum (increased UV tolerance over time)

Delayed / Therapeutic Effects

1. Vitamin D synthesis - UVB converts 7-dehydrocholesterol to Vitamin D3
2. Bactericidal / Germicidal effect - UVC destroys DNA of microorganisms
3. Desquamation - peeling of superficial skin layers
4. Immunosuppressive effect - reduces epidermal Langerhans cells (used in psoriasis)
5. Wound healing - stimulates granulation tissue formation
6. Antirachitic effect - prevention of rickets via Vit D

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Therapeutic Indications

Dermatological Conditions

Wound Conditions

Other Conditions

• Rickets - Vitamin D deficiency (general irradiation)
• Pruritis (itching)
• Psychological benefits (general UV exposure)

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Contraindications

• Photosensitive skin conditions (lupus, pellagra, xeroderma pigmentosum)
• Photosensitising drugs (tetracyclines, sulphonamides, phenothiazines, coal tar products - unless deliberate PUVA)
• Acute systemic illness (fever, tuberculosis)
• Cardiac / renal / hepatic disease (generalised UVR)
• Recent radiotherapy to the area
• Skin malignancy
• Hyperthyroidism
• Diabetes mellitus (impaired healing)
• Pulmonary tuberculosis

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Precautions

• Eyes must be protected with goggles at all times (both patient and therapist)
• Expose only the area being treated - cover surrounding areas
• Document the lamp serial number, distance, time used
• Note the patient's skin type (Fitzpatrick scale) - fair skin is more sensitive
• Allow lamp to warm up adequately before use (mercury lamps)
• Note any medications the patient is taking

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Application Technique

General (Whole Body) Irradiation

• Patient lies in cubicle; alpine sun lamp or solarium used
• Distance: 50-75 cm from skin
• Sub-erythemal doses used
• Used for rickets, vitiligo, psychological conditions

Local Irradiation

• Expose only affected area
• Kromayer lamp for wounds and localised skin conditions
• Perpendicular application at prescribed distance and time

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Special Regimens

PUVA Therapy (Psoralen + UVA)

• Patient takes psoralen (photosensitising drug) orally 2 hours before
• Exposed to UVA (solarium/fluorescent lamps)
• Used for severe psoriasis and vitiligo
• Psoralen makes DNA more sensitive to UVA, enhancing therapeutic effect

Goeckerman Regimen (Psoriasis)

• Coal tar application 2-3 times/day
• UVB irradiation once daily at sub-erythemal or E1 dose

Ingram / Leeds Regimen (Psoriasis)

• Coal tar bath before irradiation
• MED of UVB given; followed by dithranol paste application

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Dangers of UVR

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Quick Comparison: IRR vs UVR

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Summary for Exam

• UVR: wavelength 100-400 nm, three types: UVA, UVB, UVC
• UVC = germicidal; UVB = erythema + Vit D; UVA = pigmentation + wound healing
• Main lamp types: Hot quartz (Mercury vapour) and Kromayer (Cold quartz)
• Unit of dosage: MED / E1 - determined by test dose (30s, 60s, 90s exposures)
• Doses: SED < E1 < E2 (2.5×) < E3 (5×) < E4 (10×) < Double E4 (20×)
• Eyes must always be protected
• Infected wounds: E4/Double E4; Psoriasis: Sub-erythemal/E1; Acne: E2