Infrared Radiation

Infrared, sometimes called infrared light, is electromagnetic radiation with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from the nominal red edge of the visible spectrum around 700 nanometers, to 1 millimeter.

1. INFRA RED RADIATION Dr. Arjun Patel MPT- musculoskeletal and sports science 1

2. INFRA RED IR has no color, it is detected by warmth IR is emitted from any heated body Its wavelength is higher than visible light IR has a wavelength of 760nm to 1mm 2

3. ELECTRO MAGNETIC SPECTRUM INITIAL WAVES WAVELENGTH R RADIOWAVES 0.1 MM TO 100 KM I INFRA RED 750 NM TO 0.4 MM V VISIBLE LIGHT 400 NM TO 750 NM U ULTRA VIOLET 10 NM TO 400 NM XG X-RAY / GAMMA RAYS 0.01 PM TO 100 NM 3

4. CLASSIFICATION OF IR 4 IR IR A 760- 1400 NM THERAPEUTIC IR B 1400 – 3000 NM THERAPEUTIC IR C 3000NM – 1MM NON THERAPEUTIC

5. Heated material produce IR radiation Higher temperature are associate with higher frequency, & shorter wavelength TEMP α 1 / WAVELENGTH & TEMP α FREQUENCY If short IR is to be produced material must not be burnt by higher temperature used. Convenient method is to heat a resistance WIRE by passing an electric current through it Electrical heater is made up of coil of suitable resistance WIRE , i.e. nickel- chromium alloy, wound on ceramic insulator 5

6. IR LAMPS LUMINOUS GENERATOR NON - LUMINOUS GENERATOR 6

7. NON LUMINOUS GENERATOR (coil heater) IR source is a coil of WIRE wrapped around a cylindrical ceramic insulator. In this heaters WIRE glows red, thus giving some radiation in visible spectrum. Some IR lamps for therapy have WIRE embedded in insulation ceramic, ceramic is heated because of lamp which emits IR so that little or no visible radiation is emitted 7

8. Heater WIRE can also be mounted behind a metal plate or inside a metal tube which does not become hot spot but emits IR in same way IR emitter is placed at focus of reflector to produce an uniform wave 8

9. If reflector is more spherical instead of convergence of beam, it will be diverge, this is usually adapted in clinic. Reflector & emitter are mounted on a mobile metal stand which can be adjusted to alter height & angle of reflector or emitter. When lamps are switched on they require time to warm up because of thermal inertia of mass of metal & insulating material that has to be heated 9

10. Small lamps may take about 5 min. but large ones may take up to 15 min to reach maximum emission Lamps with an exposed coil give off a red glow although they are collectively designated as “ non-luminous” sources With non-luminous Exposure is in Long IR wavelength range 10

11. LUMINOUS GENERATOR (Bulb) They consist of a tungsten filament in a large glass envelope which contains inert gas at low pressure. Part of inside of glass bulb is silvered to provide a reflector Works on same principle as a simple electric light bulb Filament is heated to a high temperature around 3000 by a current passed through it 11

12. So gives out continuous spectrum in IR & visible region Oxidation(burnt) does not occur because of no oxygen, only part of inert air Radiation extends from SHORT IR to visible light to the UVR. UVR is absorbed in glass Luminous generators are sometimes called RADIANT HEAT as they emit both IR & visible light 12

13. POWER SMALL LAMPS (BOTH) 250-500 WATT LARGE, NON LUMINOUS 750-1000 W LARGE , LUMINOUS 750-1500 W Larger lamps are used to treat extensive area , but same effect can be achieved by placing small three lamps in a row 13

14. EMISSION NON LUMINOUS 3000 – 4000 NM (LONG IR ) LUMINOUS SHORT IR 5% VISIBLE 1% UVR 14

15. PENETRATION & ABSORBTION IT DEPENDS UPON: STRUCTURE VASCULARITY PIGMENTATION OF SKIN WAVELENGTH OF RADIATION 15

16. DEPTH OF PENETRATION Depth of penetration: it is depth at which approximately 63% of radiation energy has been absorbed & 37% remains 3000 nm depth of penetration is 0.1mm Increasing penetration with decreasing wavelength in short IR to a maximum penetration depth of 3 mm at 1000 nm 16

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18. CHOICE OF APPRATUS Acute inflammation/recent injury – sedative effects by non-luminous generator is more effective than luminous generator because pain relief is needed than counter-irritant effect. For chronic injury /lesion counter irritant effect by shorter IR is more effective than non-luminous generator. 18

19. CHOICE OF APPRATUS Only on part /surface of body requires treatment than single lamp will be sufficient. If several part/surface of body requires treatment than tunnel bath/combination of 4-6lamps is needed. 19

20. THERAPEUTIC EFFECT Relief of pain Mild heating – sedative effect on superficial nerve endings Stronger heating – irritate the superficial nerve endings – counter irritant effect ( pain may be because of accumulation of waste product of metabolism and IR removes that substances so relieves the pain.) 20

21. Muscle relaxation – tissue get warm – pain relief – relieve muscle spasm – perform exercise more efficiently Increased of blood supply – superficial tissue – treatment of superficial wounds and infection Arthritic condition :small joints of hand and feet 21

22. DANGERS Burns Electric shock Gangrene – area with defective arterial supply Headache – if treatment given during a hot weather.- back of head. faintness – decrease in blood pressure – brain hypoxia – either patient suddenly rises from supine position after extensive treatment Injury to eyes - cataract 22

23. Technique of application Patient Position : suitable, well supported, with area to be treated exposed. Explanation : explain nature and effect of treatment to patient Examination and testing : examine the skin to be treated and test thermal sensation. 23

24. Apparatus : If a non – luminous lamp is chosen switch it 5 min before treatment starts to allow a time to warm up Luminous lamp does not require warm up time. 24

25. Setting up Expose the skin to be treated Cover eye, a towel is sufficient Position lamp in such a way that rays strike at 90 degree to skin Set lamp at 50-75 cm for large lamp (750 to 1000 watts) Set lamp at 40-45 cm for small lamp 25

26. Instructions and warning Advise patient of required level of heat and it must not be hot as it burn. Ask patient not to touch any part of lamp or to move during treatment Alert therapist if it is more than comfortable level of heating. 26

27. Application Intensity in most IR lamp is controlled by distance. Doubling the lamp to skin distance reduce the intensity (wcm -2 ) to one quarter Tripling the lamp to skin distance reduce the intensity to one ninth 27

28. Termination At the end of treatment skin should be checked On palpation it looks mild or moderately warm Moderate erythema should be visible. Erythema tends to vary with skin color, not just temperature. 28

29. LUMINOUS HEAT LAMP Penetrates more compare to non luminous More efficient tissue heating Therapeutic effect is mostly due to heating NON LUMINOUS LAMP Does not penetrate more deeply Mostly absorbed in skin Therapeutic effect is mostly due to sensory heating 29

30. References: Clayton’s Electrotherapy: Theory and Practice - Forster & Palastanga (Ninth Edition) Electrotherapy Explained – John Low & Ann Reed (Third Edition) Electrotherapy Simplified – Basanta Kumar Nanda Basics of Electrotherapy – Subhash Khatri 30

31. Thank you 31