C14 M 3.3 Diathermy Role Name Affiliation Principal Investigator Dr. Asis Goswami Ramakrishna Mission Vivekananda University Co-Principal Investigator

Transcription

1 C14 M 3.3 Diathermy Role Name Affiliation Principal Investigator Dr. Asis Goswami Ramakrishna Mission Vivekananda University Co-Principal Investigator Dr. P.K. Nag Ramakrishna Mission Vivekananda University Paper Coordinator Dr. A. G. K. Sinha Punjabi University Content Writer/Author Dr. A. G. K. Sinha Punjabi University Content Reviewer Dr. Asis Goswami Ramakrishna Mission Language Editor Items Subject Name Paper Name Module Name/Title Case Study Module Id Pre-Requisites Objectives Mr. Jayanta Kumar Ghoshal Vivekananda University Free Lance Language Editor Description of Module Physical Education, Sports and Health Education Athlete Care and Rehabilitation Diathermy PESHE/RKMVU/14/3.3 None After going through this module the reader will be able to Understand the meaning of term diathermy Differentiate between deep heating and superficial Know the characteristics of SWD Understand the effects of SWD List the indication and contraindication of SWD Know the characteristics of MWD, Understand the effects of MWD List the indication and contraindication of MWD Keywords Short Wave Diathermy, Microwave Diathermy, Biophysics, Effects, Uses, Contraindications 1 P a g e

2 Table of content Summary Introduction 1 Short Wave Diathermy 1.1 Production 1.2 Transfer of Energy 1.3 Methods of Application 1.4 Physiological Effects 1.5 Heating Pattern 1.6 Therapeutic Usages 1.7 Dangers and Contraindications 1.8 dosage 2. Microwave Diathermy 2.1 Production 2.2 Effects and Therapeutic Use of MWD 2.3 Dosage 2.4 Contraindications 3 Pulsed Diathermy 2 P a g e

3 Summary Diathermy means thorough heating. In this module we have discussed two methods of diathermy that use electromagnetic waves to produce heating of the deeper part of body. Wave length of short wave is larger then that of microwave and it has greater penetration ability. SWD provides the deepest heating while the MD heats only structure laying few cm below the skin. Heating of subcutaneous fat is largely avoided in MWD whereas in SWD considerable heating of fat tissue do occurs along with heating of deeply placed structures such as joint capsules. The doses of both the modalities are determined on the basis of patient s reported sensation of warmth. Therefore impaired sensation and inability to dissipate heat are the absolute contraindications of both the modalities. The pulsed mode of diathermy does not produce any rise in temperature and is used in conditions of acute and subacute inflammation to enhance the rate of healing. 3 P a g e

4 Introduction Diathermy is a Greek word which means thorough heating. Heating of tissue is a well established method of treatment of ailments since antiquity. During late 1800 it was observed that with high frequency alternating current a relatively larger amount of current can be passed through the body and these currents produce a sensation of warmth but no contraction of muscles. These observation led Karl Franz Negalschmidtch to coin the term diathermy to describe the heating produced in the deeper layers of the body through the application of electromagnetic energy. The subsequent research led the development of methods of deep heating using electromagnetic waves. Earlier machines employed long radiofrequency waves which were replaced afterwards by short radio waves owing to technological ease. Almost parallel to the development of short wave diathermy, another group of deep heating devices were developed that used microwaves to produce deep heating. At the same time it was also observed that exposure to ultrasound waves can also produce heating of the deeper part of body. These devices were referred as diathermy and according to the kind of energy used in these devices were named as long wave diathermy, short wave diathermy, microwave diathermy and ultrasound diathermy. Long wave diathermy is now no longer used in therapy. The characteristic feature of these devices is that they all increase the temperature of deeper tissue without producing corresponding elevation of that of the superficial tissue. Soon after the non-thermal effects of ultrasound were discovered, it was no longer considered as diathermy but a therapeutic modality of its own kind. Ultrasound is described in another module. In the present module we will discuss about biophysics, production, effects, uses and contradictions of short wave diathermy (SWD) and microwave diathermy (MWD). 1. Short Wave Diathermy (SWD) Short wave diathermy is the application of short radiofrequency waves to produce heating of the body tissue. Radio frequency waves are the part of electromagnetic spectrum that has wavelength of 3 30 meters and the frequency range of 100MHz to 1 KHz. These waves are widely used in radio and television communication. Radio waves are classified into three bands -long, medium and short waves. The waves of MHz are called short waves that have wavelengths ranging from 30 meter to 300 meter. The frequency of short waves allotted for medical use is MHz and it has the wavelength of about 11 meter. All electromagnetic waves possess certain similar properties. They carry electric and magnetic energy and as they do not require any medium to travel, they can pass through a vacuum without any hindrance. When an electromagnetic wave passes through a substance, its electrical and magnetic fields interact with the electrically charged particles of the substance and produce several effects in accordance with their energy levels. The energy content of electromagnetic 4 P a g e

5 waves is directly proportional to the frequency and as the frequency increases the energy content of the waves also increases. In comparison with other electromagnetic spectra such as X-rays and gamma rays, radio waves have the lowest frequency and thus they contain relatively much less energy. The energy quanta of X-rays and gamma rays are much higher. Therefore when these waves are absorbed in the body they can produce ionization of water molecules and destruction of cells. These ionizing radiations are used in radiotherapy to destroy the cancer cells. Short radio waves are non- ionizing radiations and as such they do not have any destructive effect on cells. When absorbed in the body these waves make the molecules and the atoms vibrate rapidly, which leads to production of higher frequency electric current within the tissue. It is the high frequency current generated within the tissue that serves to heat the tissue. Fig 1: Short Wave Diathermy Unit 1.1 Production The generation of electromagnetic radiation is the result of acceleration of electric charge. The artificial production of radio waves requires a source of high frequency current. The high frequency current is produced by discharging a condenser via an inductance of low ohmic resistance. The basic circuitry for this is known as oscillator circuit or LC circuit that consists of a capacitor (device that stores charge) and an inductance (coil of metal having low ohmic resistance) incorporated in a an electronic valve circuit. The frequency of produced current depends on the value of the capacitance and the inductance and it is possible to generate high frequency electrical currents of different frequencies by suitably selecting the capacitance and the inductance. In most of the short wave 5 P a g e

6 diathermy devices the inductance and the capacitance are so selected that the oscillator circuit produces a high frequency electric current of MHz which emits short waves of similar frequency. 1.2 Transfer of Energy The principle of the transfer of the generated energy to the patient`s body is similar to the working principles of an electric transformer and a radio-transistor that make use of the phenomenon of electromagnetic induction. In this phenomenon when two electric circuits are kept in proximity to each other, the magnetic field of the electric current passing through one circuit sets up electric current in other circuit without being in direct contact with the first circuit. When the product of the inductance and the capacitance of both the circuits match, there occurs maximal transfer of energy and the current induced in the other circuit has the same frequency as that of the current produced in the first circuit. A short wave diathermy machine consists of two circuits oscillating circuit and resonator circuit. The oscillating circuit produces high frequency current. The resonator circuit has an inductance coil, closely placed to the inductance coil of the oscillating circuit, a variable capacitor and electrodes. Part of the patient s body is placed between the electrodes and it acts either as a capacitor or as an inductor. Since the patient is also the part of the electric circuit, the resonator circuit is also known as patient circuit. For maximal transfer of energy the product of the capacitance and theinductance of the patient circuit should match with that of the oscillator circuit. However the inductance and the capacitance of the resonator circuit vary according to the body part and the size and placement of electrodes and is different for each application. Therefore in each application the value of variable capacitor is adjusted to ensure that the product of the inductance and the capacitance of the resonator circuit is matched to that of the oscillator circuit. This process is known as tuning and it is similar to tuning of a radio set. 1.3 Methods of Application of SWD There are two principle method of SWD application capacitor field method and cable method. In capacitor field method the body part is placed between two rectangular electrodes. The electrodes are separated form the skin by a layer of insulating material. Electrodes serve as a two plates of capacitor and body tissue and insulating material constitutes the dielectric. This method of application utilizes the effects of oscillating electric field. 6 P a g e

7 2a: Contraplaner method 2b: Co-planner method Fig 2: Application of SWD by two techniques of capacitor field method Cable method is also known as inductothermy. In this method an inductive coil applicator is used to set up an oscillating magnetic field and the body tissue serves as the inductance. There are two types of coil applicators used in inductothermy - cable and monode. A length of cable is spirally wrapped around the body part whereas in monode a compact coil is mounted on a plastic housing to be placed over the body part. A layer of insulating material (towel) should be placed over the skin while using both types of applicator. Inductothermy method utilizes the effect of oscillating magnetic field that sets up eddy current within the tissue. The cable method is used for treatment of an extensive area which cannot be covered under capacitative electrodes. It is also used to treat irregular areas of the body such as hand and feet. 1.4 Physiological Effects of SWD Owing to shorter pulse duration of the electric impulse the high frequency current does not stimulate motor or sensory nerve. As the current is evenly alternating, it does not give rise to accumulation of chemical substances in the tissue. The primary effect of SWD is heat production within the tissue. The subsequent physiological effects such as increased blood flow, increased metabolism, pain relief, increased extensibility of the body part, muscle relaxation etc. are the effect of heat. The extent of temperature raised during SWD application depends on SAR (specific absorption rate) which is the rate at which energy is absorbed by a unit tissue mass (unit watt / kg). The factors that influence SAR are the electrical properties of the tissue and the magnitude of electromagnetic field in the tissue. According to the electrical behaviours the living tissue can be considered that they are composed of three types of molecules charged, dipoles and non-polar. 7 P a g e

8 The varying electromagnetic field of SWD affects the charged particle the most. Under influence of SWD there occurs acceleration of the charged molecules, rotation of dipoles and distortion of the electron cloud of non-polar molecules which produce electric current and generate heat in accordance with Joule s law of electricity. The acceleration of the charge molecules produces highest heat followed by the rotation of dipole and distortion of the non-polar molecules. Therefore during SWD application the tissue having high proportion of charged particles such highly vascularised tissues are heated most. 1.5 Heating Pattern of SWD Unlike superficial heating modalities such as infra-red rays or paraffin wax bath the heating pattern of SWD is highly complex and strongly influenced by the technique of application. SWD has the ability to produce differential heating of the body tissues. SWD can elevate the temperature of both superficial and deep tissues. Depending on the size and placement of electrodes superficial heating as well as deep heating can be produced by capacitor method. Inductothermy produces negligible heating of fat and largely produces heating of superficial muscles. In capacitor field method the heating pattern differs according to the relative arrangement of tissues in the pathways of the electric field. When different tissues lie parallel to the electric field, the density of the field and the heat production in the tissues of high dielectric constant become the greatest. This happens when two electrodes are arranged in such a way that electric field passes longitudinally through limb. In this situation muscles and blood vessels are heated most while least heating takes place in fat and bone. When the tissues are arranged transversely across the electric field, the density of the field becomes uniform and the tissues of low dielectric constant such as subcutaneous fat tissue are heated the most. Since the purpose of application of SWD is to produce deep heating, in such arrangements the superficial heating is minimized by selecting the electrode of suitable size, adjusting the spacing between the electrode and skin and by positioning the electrodes in relation to each other. Besides direct heating by generation of electric current within tissue SWD also produces indirect heating through conduction. The heated tissue transfers thermal energy to the adjacent tissue and elevates their temperature. It is in this manner the heat of the deeper tissues is transferred upwards to skin and sensation of warmth is felt. 1.6 Therapeutic Use of SWD The SWD allow greater depth of heating then that occurs with superficial heating agents. Heating of tissue leads to increased blood flow to the part and a number of related physical and metabolic changes. The other uses of heating are to increase the extensibility of deep collagen fibers, decrease joint stiffness, relieve deep pain and muscle spasm. Heat also produces sedative and counter irritant effects that serve to reduce pain. Rise in muscle temperature contributes to 8 P a g e

9 increased muscle relaxation and increased muscle blood flow, which make the movement efficient. Application of heat aids in resolution of subacute and chronic inflammation. The increased blood flow brings cells, enhances their metabolic activity and contributes to accelerated resolution of inflammation. SWD is particularly beneficial for treating deeply placed structures such as the hip joint. In conjunction with other electrotherapy modalities and exercises it is very commonly used in management of rheumatoid arthritis, osteoarthritis, capsulitis and tendinitis of deeply placed structures. Low back pain, knee pain and muscle spasm associated with trauma and inflammation responds well to SWD. SWD is sometimes also used in cases of infection such as pelvic floor inflammation and infected surgical wound to bring about early resolution of inflammation and facilitate healing. 1.7 Danger and Contraindication of SWD Burn is the inherent danger of any heating modality and SWD is no exception. Concentration of electric field and inability of the tissue to dissipate the generated heat have the potential to raise the temperature of the tissue beyond the safety limits and produce destruction of the tissue. Therefore every attempt should be made to ensure that SWD is not administered where there is any chance of damage to the tissue. The contraindications ( the conditions where SWD, should not be used) of SWD include metal implant, impaired thermal sensation, haemorrhage, venous thrombosis, arterial disease, inability to communicate, inability to control movement of the body, ischemic tissue, pregnancy, malignant tumor and recent radiotherapy. Metal and sweat causes concentration of electric field and overheating. When the venous or arterial supply of the part is not proper, tissues are not able to dissipate the heat which could result in excessive heat build-up. The perception of heat by the patient is the only way of knowing the dose of SWD. Therefore in conditions where the patient is unable to perceive and communicate the thermal sensation the chance of excessive heating is very high. The recent haemorrhage (bleeding) and acute inflammation may be aggravated by application of heat. Owing to fear of uncontrolled proliferation of cells in response to heating SWD is not applied in malignancy and on pregnant uterus. 1.8 Dosage The dose of SWD is decided by the patient`s perception of warmth. The heating sensation is usually very mild. During application of SWD the patient should feel much less warmth than that felt during application of hot pack. The following four dose levels are used in clinical practice. 9 P a g e Level 1 imperceptible heating Level 2 mild perception of heat Level 3 comfortable perception of heat Level 4 - vigorous heating as felt during application of hot pack

10 Level 1 and 2 doses are used in acute inflammation. Level 3 is used in chronic inflammation and long standing cases. Level 4 dose is normally not used in day to day practice as it may increase deeper tissue temperature to dangerous level. Depending on the condition treatment is applied for minutes either daily or on alternate days. 2. Microwave Diathermy (MWD) Microwaves are the part of electromagnetic spectrum that lies between radio waves and infra-red rays. The wavelength of microwaves ranges from 1cm to 1 meter with frequency ranging from 30 GHz to 300 MHz. The artificial production of MW stared during 1930s following the quest for development of a sophisticated radar system. For therapeutic purposes MWD were available during 1960s and 1970s. The most common use of microwavse is in the area of phone communication and radar. These waves are also used in establishing communication system in satellite and rocket. For medical use three frequencies of MWD are allotted. Among them the frequency of 2450 MHz which emits a wavelength of cm is most commonly used. The use of other two frequencies (915 MHz and MHz) is not so common. Microwave produce heating is a now a common knowledge due to widespread of use of microwave oven in the kitchen. Barring a few characteristics the use, effect and indications of MWD are similar to that of SWD. In the field of sports medicine MWD is more commonly used than SWD. 2.1 Production of MWD MWD is produced by a device called magnetron. This device generates high frequency current directly form high velocity electron motion. These currents are collected and sent to an emitter through coaxial cables. The emitter is mounted in front of a metal reflector that emits microwaves in only one direction. The power supplied to magnetron is controlled to regulate the output of magnetron. The MWD machine has a power output meter and a timer to precisely control the exposure. Like SWD, MWD can also be delivered in continuous or pulsed mode. 10 P a g e

11 . Fig 3: MWD unit 2.2 Effects and Therapeutic Use of MWD Microwave obeys all laws of electromagnetic waves such as reflection, refraction, steering and absorption and inverse square law. Therapeutic microwave is largely absorbed in the first few cm of the body. The half value distance of MWD in a human body is about 3.5 cm. The absorption of microwaves generates a high frequency current in the body owing to the movement of charged particles, rotation of dipoles and electron orbit distortion. As a result of the absorption heat is also produced. Increased temperature brings about an associated increase in the blood flow to the muscles. It also improves the extensibility of muscle tissue. The pattern of heating after exposure to MWD depends on the electrical properties of the tissue and the density of microwave in the area. Microwave is strongly absorbed in water and water containing tissue but not in fat. Therefore with MWD it is possible to raise the temperature of the muscle while avoiding heating of subcutaneous fat- an advantage over capacitor field method of SWD, which makes it the modality of choice in treating athletic injuries. Metal does not transmit microwave; thus when microwave encounters a metal surface it gets reflected. This causes concentration of energy and overheating. This accounts for the observation that MWD produces maximal heating at the tissue interface and near to metal implant. Owing to selective heating properties of muscle tissues MWD is most commonly used in subacute and chronic inflammation of muscles as encountered in muscle contusion and strain. Combination of MWD with stretching helps restore the length of tight / contracted muscles. It is a suitable method to treat superficial muscles and joints closed to surface but not for deeply placed joints such as one in the hip. It can successfully increase the temperature of small joints of fingers. 11 P a g e

12 2.3 Dosage of MWD Treatment time is usually minutes. The intensity is regulated by the sensation of warmth reported by the patient. 2.4 Contraindications of MWD Like SWD, MWD should not be applied to areas of diminished thermal sensation, defective arterial and venous circulation. Acute hemorrhage and immediate inflammation are the absolute contraindications of heat therapy. In addition to that metal in the tissue such as plates, screws, cardiac pacemaker etc. should be avoided as there may occur considerable reflection leading to excessive temperature rise in surrounding tissues. 3. Pulsed Diathermy The above discussion pertains to continuous application of short wave and microwave. Advancement of technology has made it possible to deliver SWD and MWD in pulsed mode where the flow of wave transmission is interrupted at regular interval to give pulses of energy of variable durations. Pulsed mode delivers relatively less energy. If a little heat is generated during this period, it is rapidly dissipated during off period and there is no heat build-up in the tissue. Therefore pulsed mode is also known as non-thermal therapy. With regard to the physiological effects of pulsed SWD and MWD two different views are expressed. One view claims that the effects of MWD are actually the effects of very mild imperceptible heating. The pulsed mode is considered to minimize the intensity of thermal effects and utilize the effect of very mild heating on the metabolic functioning of cell involved in inflammation and healing process. The other view states that pulsed diathermy may produce some effects which are not due to heat but due to other mechanisms that may lead to enhanced functioning of cells. Alteration of ionic environment of cells due to the movement of ions and molecules under the influence of oscillating electro-magnetic field leading to alteration in membrane potential and permeability of cells and utilisation of absorbed energy for chemical works are some of the suggested non-thermal effects of pulsed diathermy. However, it should be noted that these explanations are entirely speculative. Nevertheless some clinical studies have demonstrated that application of diathermy in pulsed mode accelerates wound healing and promote regeneration of nerves. Pulsed SWD and MWD are used in acute and subacute inflammation where continuous diathermy is contraindicated.. 12 P a g e