Infrared Therapy

Original Editor - User Name

Top Contributors - Vidya Acharya, Cindy John-Chu, Kim Jackson and Sai Kripa  

This article or area is currently under construction and may only be partially complete. Please come back soon to see the finished work! (28/06/2021)

Introduction

Infrared (IR) or thermal radiation is a band of energy in the complete electromagnetic spectrum. IR are the radiations of longer wavelength than the red end of the visible spectrum and extend to the microwave region, i.e., from 760 nm to 1 mm. IR radiation is generated by Sun. Many ancient therapies have utilized sunlight for wound healing and pain relief. When Sun rays reach the ground, they get absorbed by gases or water molecules in the atmosphere. The human body is made of 70% water, so it can potentially accumulate a large amount of energy that could modulate biological processes by strong resonant absorption of IR radiation from sunlight mediated by water molecules.

Electromagnetic Spectrum

IR includes wavelengths between the 780 nm to 1000 μm. IR is divided into different bands: Near-Infrared (NIR, 0.78~3.0 μm), Mid-Infrared (MIR, 3.0~50.0 μm) and Far-Infrared (FIR, 50.0~1000.0 μm) as defined in standard ISO 20473:2007 Optics and photonics -- Spectral bands.Classification

The classification of the International Commission on Illumination (CIE) has three sub-divisions for the IR radiation

Type	Wavelength
IR A (Near IR)	700-1400nm
IR B (Mid-IR)	1400-3000nm
IR C (Far-IR)	3000 nm– 0.1 mm

An alternative classification provided in ISO 20473

Any heated body emits infra red; Sun also emits infrared radiation. Any material with temperature above absolute zero emits IR. IR radiations are produced in all matter by molecular vibration; the molecular movement causes infrared emission of different wavelengths and frequencies. The frequencies at which maximum radiations are emitted are proportional to the temperature which means higher the temperature high the frequency and so shorter the wavelength.

The Near infrared are also known as 'luminous' as they have some visible light with wavelength of 770 to 1500 nanometers. The luminous source is found to be more effective in tissue-heating as it penetrates deeper and energy is distributed in larger areas of the tissues. The Far infrared also called as non-luminous are within 1500nm to 0.1 mm. the non-luminous with peak around 4000nm is absorbed in the skin.

Production of Infrared

Different kinds of lamps are used for production of therapeutic infrared:

Non-luminous generator - An electric current is passed through a coil of wire wound on an insulating material (like porcelain/fireclay) which produces heat. The infrared emitter is placed at the focus of parabolic reflector to reflect the radiations in an uniform beam. The heated wire and heated material emits IR. Non-luminous requires some time to heat up before the emitted rays reach maximum intensity and so must be switched on at an appropriate time prior to use .

Luminous generators - IR is produced by incandescent lamps in the luminous generator. The lamp consists of a wire filament (tungsten) enclosed in a glass bulb that may be evacuated or filled with an inert gas at a low pressure. When an electric current is passed through the tungsten filament, it gets heated and emits IR, visible and few ultra-violet rays. The front of the bulb is red to filter out shorter visible and UV rays.

Power varies, for smaller lamps is 250 to 500 W for both generators and for large non luminous - 750 or 1000W and large luminous 600 to 1500 W.

Absorption and Penetration of IR

Some rays are reflected from the skin surface. Some penetrate in the skin-get scattered, refracted and ultimately absorbed in tissues. Water and protein in the tissues strongly absorb IR. Research suggests penetration of IR depends on the structure, vascularity, pigmentation of skin and wavelength of the rays. Penetration depth is the depth at which approximately 63% of radiation energy is absorbed.Penetration increases with decreasing wavelength. Penetration depth is about 0.1mm at around 3000nm; and about 3mm around 1000nm wavelength.

Physiological Effects

Infrared radiations cause:

• local cutaneous vasodilation due to the release of chemical vasodilator (histamine) as well as possible effect on the blood vessels, occurs after 1-2 mins
• evident erythema the rate and intensity of erythema depends on rate and degree of heating.
• reflex dilation of other cutaneous vessels occurs to maintain normal heat balance
• prolonged heating leads to sweating leading to cooling

Therapeutic Uses

Infrared is used for the following purposes:

• pain relief
• decreases muscle spasm
• increases the sensory nerve conduction velocity, increase in endorphins influencing the pain gate mechanism
• acceleration of healing and tissue repair- pressure sores
• used prior to electrical stimulation/testing or biofeedback to make the skin a better conductor

Application

Patient is placed in a comfortable position and the area to be treated is exposed. Nature and effects of treatment are explained. Skin is examined and thermal sensations are tested. Eyes are shielded in case they are irradiated. To achieve maximum penetration, the lamp is placed at right angles to area to be treated.Distance from the lamp can be about 60-75 cm for large lamp (750-1000W) and 45-50cm for smaller ones. Intensity of heat is controlled by altering the position of the lamp or in some lamps by altering the resistance thereby the current to the element. Non-luminous lamp has to be switched on up to 15 mins before application to allow maximum emission.

New development

Infrared Emitting Materials for Clothing

Sports professionals, especially elite athletes, use far-infrared (FIR)-emitting garments to enhance exercise performance and recovery.

Dangers

• Burns
• Skin irritation
• Eye damage
• Dehydration
• Low BP
• Defective arterial blood flow

Contraindications

• Impaired cutaneous thermal sensations
• Defective arterial cutaneous circulation
• Dermatitis or eczema
• Tumors
• Skin damage due to ionizing radiation
• Fever

Resources

• bulleted list
• x

or

1. numbered list
2. x