ELECTROMAGNETIC WAVES FOR THERAPYThese are: UV-A: wavelengths between 400 nm and 315 nm UV-B: wavelengths between 315 nm and 280 nmUV-C: wavelengths between 280 nm and 100 nm.UV-C radiation is used to sterilize things when you don't want to boil them because UV-C, at sufficiently high intensities, destroys bacteria. It does this by damaging the bacterial DNAUV-B and A have an extremely low penetration depth, so most of the absorption of UV is by the skinUltraviolet radiation for therapeutic application is usually produced by current flow through mercury vapour. Mercury under reduced pressure is contained in a sealed envelope of quartz or special glass with an electrode inserted in each end
Effects of Ultraviolet RadiationThe effects of ultraviolet radiation are mainly non-thermal and due to cellular damage and protective responses:- An increased blood supply to the skin results from dilation of the capillaries and arteriolesProduction of vitamin D. Ultraviolet radiation in the range 250 to 300 nm initiates a sequence of chemical reactions by which vitamins of the D group are synthesizedSterilization. Shorter wavelength ultraviolet radiation (UV-C, around 250 nm) is effective in destroying bacteriaDesquamation occurs some time after exposure to ultraviolet raysInfrared radiationInfrared radiation is produced (and absorbed) by all materials at temperatures above absolute zeroAbsorption of infrared radiation results in changes in molecular and atomic motion of a material5The main effects of IR treatment An increase in metabolic rate in the superficial tissues .As a result there will be an increased demand for oxygen and an increased output of waste products.Dilatation of capillaries and arterioles due directly to the heating and also as a reflex reaction to the presence of increased concentrations of metabolites. Sensory sedation. Mild heating has a 'sedatory' effect on sensory nerves and is thus useful for the relief of pain.Muscle spasm relief. This results from both the effect of heat on nerve fibres and the direct effect of heat which is transferred to muscle from the superficial tissues
Penetration of radiation into skin in the infrared to ultraviolet region of the electromagnetic spectrum
Electrical SafetyElectrical shock :-are macroshock and microshockMacroshock:-current flows from the body surface, throughthe skin and into the body.Microshock:-A very small current applied directly to the heart via this pathway can be fatal
Earthling of mains-powered apparatus casing.
The neutral wire is nominally at earth potential (zero volts) and the active wire is at a high potential. The active line connects through a power meter to a switch and fuse or to a circuit breakerpower outletspower outlets have three terminals; an active, a neutral and an earth terminal. The earth terminal is connected to a wire which is physically connected to earth at the building
shock has occurred because the earth wire is damagedThe fuse in the active line will not protect the person from receiving an electric shock (fuse rate)ELECTRICAL SAFETYhappen the active wire must short-circuit to the earthed casingThere are two commonly used ways - by using a core balance relay or a protected earth-free supply.Core Balance Relayscurrents flowing in the active and neutral wires are equal. When an electric shock occurs the current in the active wire will be slightly greater than that in the neutral wire. The currents in the wires are in opposite directions and when they are equal no current is induced in the sensing coil. If the currents are unequal a current proportional to the difference in active and neutral current is induced in the sensing coil. The induced current is amplified and used to operate a magnetic relay which disconnects both the active and neutral supply lines.
Earth Free Supplies
Earth Free Supplies
Isolation with earth leakage detection.MICROSHOCKProtection is afforded at two levels: by using apparatus which meets appropriate safety standards andby appropriate protection built into the mains supply
PATIENT TREATMENT AND ELECTRICAL SAFETYPatient treatment areas in hospitals are distinguished according to the kind of procedures or treatment being used and different safety standards apply to the mains supply in each case.Three types of treatment area are distinguished:-Cardiac protected electrical areas areas which are suitable for carrying out procedures which involve direct electrical connection to the heart2. Body protected electrical areas:-which are suitable for carrying out procedures which do not involve direct electrical connection to the heart but which do involve the patient being in direct electrical contact with electromedical apparatus3. Other patient areasApparatus which is not electrically connected to the patient
When a piece of electromedical apparatus has a patient circuit then the patient circuit itself can be either class CF, BF or B.class CF patient circuit is the most safe. If the leakage current to the patient circuit is normally below 10 A and below 50 A even when a fault condition exists2. class BF patient circuit is macroshock protected. The normal leakage current is below 100 A and the current which can flow when the earth lead is broken is below 500 A3. class B patient circuit affords a minimum level of macroshock protection
BFCFFlowchart for the safe application and use of electromedical equipment