HIGH FREQUENCY CURRENTS
Aim
The purpose of this subject is to enable you to:
Learn the uses of different high frequency currents in physiotherapy.
Develop application skills of different high frequency currents.
Know the physiological effects, indications, contraindications and precautions for different high frequency currents.
Learning assumed to be in place:
Heat conduction
Heat transference
Heat regulation by the body.
Outcomes
At the end of this module you should be able to:
Describe the terms used in medium & high frequency currents.
Explain the therapeutic production of medium & different high frequency currents.
Explain the effects of different methods of application in high frequency currents.
Explain the indications for medium & high frequency currents.
Explain the dangers and contra-indic
ations of medium & high
frequency currents. Explain the precautionary measures that need to be taken when using medium & high frequency currents.
Demonstrate a safe treatment on each other under supervision using medium & high frequencycurrents.
Assessment Criteria
You should explain the different terms used in medium & high frequency currents.
You should explain and discuss the uses and physiological effects of medium & different high frequency currents.
You should explain the indications, contraindications and dangers of medium & different high frequency currents.
You should demonstrate practically a safe application of medium & high frequency currents on each other under supervision.
Course Content
Short wave diathermy (SWD)
- Production of SWD - Physiological Effects - Therapeutic effects - Techniques: - co-planar - Contra planar - Crossfire - Pulsed short-wave diathermy. - Indications
- Precautions - Contra-indications - Dangers
- Practicals
Ultrasound
- Production and Transmission - Physical Characteristics - Physiological Effects
- Application techniques used (underwater & Contact methods)
- Pulsed Ultrasound - Indications
- Contra-indications - Dangers
- Practicals
Interferential Therapy/Current(Medium Frequency current).
- Production of I/F therapy - Physiological Effects
- Application techniques (Different Frequency ranges and Mode shapes)
- Indications - Precautions - Contra-indications - Dangers
- Practicals
Ultraviolet therapy (UVL)
- Types of UVL (including air-cooled and water-cooled lamps).
- Physiological Effects - Therapeutic effects
- Dosages and progression of therapy - Indications
- Precautions - Contra-indications - Dangers
- Practicals (Demonstration)
PRINCIPLES OF THERAPEUTIC HEATING
Heat is a form of energy. Every organism produces heat (a by-product of metabolism), and this heat may either be stored in the body or lost to the environment by radiation, conduction or convection.
Addition of heat to an object/body may cause expansion or rise in temperature.
SELF STUDY
Specific heat capacity, Laws of electromagnetic waves (reflection, refraction, absorption, inverse squares).
Thermal conductivity of different tissues. Heat regulation by the body.
PHYSIOLOGICAL EFFECTS OF HEAT
Application of external heat to the tissues produces a number of changes in the body. The extent of the physiological response depends on:
The size of the area exposed. The intensity of heat applied. The duration of irradiation.
The depth of absorption of specific irradiation.
The thermal conductivity, specific heat capacity and density of the skin and tissues irradiated.
Age of the patient.
The integrity of the cardiovascular and nervous systems. The pathophysiology of the area being treated.
LOCAL EFFECTS OF HEAT
1. Increase in metabolic activity.
Any chemical change that is capable of being accelerated is accelerated by a rise in temperature, (Vant Hoff’s statement). Heating of tissues results in a change in temperature and hence an increase in the metabolic rate. The rise in the metabolic rate is directly proportional to the amount of heat produced in the tissues. This results in an increase in the demand for oxygen and
nutrients by the tissues and a subsequent increase in the production of waste materials (metabolites). The metabolic rate of skin and muscle depends in part on the temperature. The rate increases by 30% for a rise in temperature of 1oC. Conversely, the metabolic rate decreases with a fall/decrease in
temperature.
2. Increase in Blood flow
The metabolites released as a result of increased metabolic rate act on the walls of the capillaries and arterioles causing vasodilation of these vessels. Heat also has a direct effect on the blood vessels causing vasodilation
particularly in the superficial vessels where heating is greatest. Stimulation of the superficial nerves also causes reflex dilatation of the vessels.
Vasodilatation results in:
- increase in blood flow to the treated area thus supplying it with oxygen and nutrients.
- Removal of metabolites.
- Erythema of the skin. This appears as soon as the area becomes warm and disappears when the exposure to heat ceases. Heat also decreases the viscosity of the blood resulting in an increased blood flow.
3. Effects of heat on nerves
4. Changes in extensibility of collagen tissue
Collagen exhibits elastic properties and when heat is applied, the tension in the tissues is markedly reduced. A low tension stretch during or immediately after heat application results in elongation of the tissues.
INDIRECT EFFECTS OF HEAT Muscle tissue
The rise in temperature induces muscle relaxation and thus increases the efficiency of muscle contraction. This is because the increase in blood supply results in optimum muscle relaxation.
General rise in body temperature
As blood flows through the tissues in which there is a rise in temperature, it becomes heated and carries the heat to other parts of the body. As the heat becomes extensive and prolonged, there is a general rise in body temperature and this leads to dilation of the superficial blood vessels because of the
stimulation of heat regulatory center in the hypothalamus. Fall in blood pressure
Heat decreases the peripheral resistance of the blood vessels. This is due to generalized vasodilation and the decrease in the viscosity of the blood.
Increased activity of sweat glands
THERAPEUTIC EFFECTS OF HEAT Pain relief
- There is increased blood flow, and therefore removals of metabolites. - There is also stimulation of heat receptors.
Increase in joint range of movement - Increase in extensibility of collagen tissue. - Analgesic effect.
Reduction of muscle spasm
- Removal of chemical irritants through circulation thus breaking pain – spam cycle.
- Muscle relaxation.
Promotion of healing
- Increase in blood flow to the area thus providing nutrients and removing metabolites.
Control of infection
- Dry heating helps drying up the infected tissue thus diminishing the rate of replication
of the micro organisms.
Resolution of chronic oedema
- Increased reabsorption of exudates as a result of vasodilation. Prophylactic in preventing pressure sores
- Increased blood flow to the area reduces the risk of skin break down.
Dangers
Burn- may be due to overdose,
PRINCIPLES OF PAIN RELIEF Definition:
Pain is defined as an unpleasant sensory or emotional experience associated with actual or potential tissue damage, or describe in such damage. Pain is always subjective. Each individual learns the application of the word through experiences related to injury in early life. It is unquestionably a sensation in a part of the body, but it is also unpleasant, and therefore also an emotional
experience.
Many people report pain in the absence of tissue damage or any likely pathophysiological cause. Usually this happens for psychological reasons. Unfortunately there is no way to distinguish their experience from that due to tissue damage. Pain may be acute or chronic.
Acute pain – persists for less than 6 months.
- Usually symbolizes the presence of a disease/injury and subsides as healing occurs.
Chronic pain – Persists beyond the usual course of an injury/disease. May recur every few months or years.
May be cause by prolonged dysfunction of the central or peripheral nervous systems.
TYPES OF PAIN
1. NOCICEPTIVE PAIN
Cutaneous nociceptors Aδ and C fibres. Nociceptors are also in somatic structures e.g. muscles, tendons, joints and fascia.
2. NEUROPATHIC/NEUROGENIC PAIN
Arises as a result of malfunctioning of the central nervous system and/or the peripheral nervous system.
Usually burning, stabbing or shooting pain
Mostly associated with clinically evident sensory loss Often associated with autonomic instability
Allodynia to cold and movement occurs
3. PSYCHOGENIC PAIN - Chronic pain
- Psychological factors contribute towards generation and maintenance of this type of pain.
- The patient believes that they have pain although there is no organic basis for the pain.
MECHANISMS OF PAIN RELIEF
1. HEAT
2. GATE CONTROL
threshold cutaneous mechanoreceptor pass up the dorsal column to the brain, they give off collaterals on entering spinal cord. These collaterals terminate on the terminals of the Aδ and C fibres in the substantia gelatinosa (transmission cell) and partially excite them such that when the nociceptive stimulus reaches the terminals, it finds them in a refractory state. The quantity of the neurotransmitter that is subsequently released from the nociceptor terminals in response to the impulse is reduced or even abolished and the “gate” is said to be closed. This is called presynaptic inhibition (peripheral modulation of pain).
In addition to the mechanoreceptors that inhibit the nociceptor stimulus presynaptically there is also central modulation of the nociceptive stimulus. The Aδ nociceptors fibres running in the spinothalmic tract also give
collaterals at the level of the brain stem. These collateral branches via the reticular formation, stimulate fibres that travel down to the spinal chord to inhibit nociceptors at the original level. This is called central modulation of the pain.
3. ENDORPHIN THEORY
SHORTWAVE DIATHERMY
TERMS USED
SHORTWAVE DIATHERMY: means of producing therapeutic heat in the tissues by the use of radio waves of high frequency.
CONVERSIVE HEATING: a relatively uniform heating produced by the
conversion of electrostatic or electromagnetic fields into heat within the tissues. ELECTROSTATIC FIELD: is set up between two electrodes by the application of a current to the electrodes.
ELECTROMAGNETIC FIELD: is set up around the loops of a coil through which a current is passing.
A CONDENSER/CAPACITOR: consists of two metal plates separated by an insulator. It stores electrical energy.
A DIELECTRIC: is the insulating (non – conducting) material between the metal plates of a condenser.
The CONDENSER FIELD METHOD: uses the patient in the circuit as part of a condenser, so that the electrostatic field is set up in the tissues.
INDUCTOTHERMY: the patient’s tissues are placed in the electromagnetic and electrostatic fields created when a high frequency alternating current is passed through the coil.
Production of Shortwave diathermy
The shortwave diathermy machines used by physiotherapists utilize the frequency of 27.12MHZ and a wavelength of 11m.
Shortwave diathermy is produced from two main circuits:
The machine circuit, which produces high frequency current and amplifies its intensity.
The electrostatic field: in the condenser field method, electrostatic field is created by including the patient’s part / tissue as part of a condenser. In this method two electrodes are applied to the part, with spacing between the
electrode and the skin. Electrodes are condenser plates and the patient’s tissues together with the spacing are dielectric of the condenser.
The electromagnetic field: in the inductothermy method, a thick insulated cable is used to complete the circuit from the machine. The cable is coiled around the tissues but separated by spacing. Two electric fields are set up in this method. Firstly the electromagnetic field is set up around the center of the cable and secondly, the electrostatic field is set up between its ends. These fields will be concentrated in the tissues.
The basic events which take place when SWD is applied to the tissues: Effects of electrostatic field:
- free ions in the tissue fluid move back and forth along the lines of force as the charge alternates on the condenser plates. Friction will occur resulting in heat production.
- the dipolar molecules in the tissue (such as water molecules) will rotate and orient themselves towards the opposite charge on the condenser plate. Friction will occur resulting in heat production.
- Non- polar molecules e.g. fat, will undergo distortion of their
electron cloud. There will be minimal friction and minimal / little heat will be produced.
Effects of an electromagnetic field. Eddy currents will be produced. These will result in friction of the tissue particles and also friction from
electrostatic field reaction, heat will be produced.
with low resistance such as those of high fluid content (Blood and Muscle). Very little heat will be produced in tissues with high resistance such as fat and bones.
Therapeutic uses of SWD
The relief of traumatic and rheumatic pain Reduces muscle spasms
Resolution of chronic inflammation To promote healing of open skin areas. To control chronic infection
To increase extensibility of fibrous tissues i.e. tendons, joint capsules and scars.
Dosage
Duration of treatment: 15 – 20 minutes for maximum increase in circulation. Shorter durations will no achieve maximum physiological effects.
Intensity: The patient must feel mild comfortable warmth not a burn. The therapist should allow 2 – 3 minutes for the intensity to build up to a desired level. This is because in SWD, heat is not produced instantly, but only after a series of reactions.
Frequency of treatment: treatments can be given daily or alternate days, but refer to the Doctor if no improvement of symptoms after 12
Indications Sprains Strains
Capsule and tendon lesions Chronic rheumatoid arthritis Joint stiffness
Haematoma Bursitis Synovitis Sinusitis
Pelvic inflammatory Disoder Abscesses
Contraindications
Over malignant tumors Over ischaemic tissues
Moderate and excessive oedema Over wet and adhesive tape Metallic implants
Fever
Pacemakers Haemophyllia Tuberculous joints
Impaired thermal sensation Unreliable patients
Deep X-ray therapy
Acute infection / inflammation. DVT
BP abnormalities
Techniques of SWD application
1. Coplanar technique: electrodes parallel to the part to be treated.
- For superficial structures
2. Contraplanar technique: the part to be treated is inbetween the two electrodes. For deeper penetration e.g. joints
3. Cross – fire technique: The electrodes are placed diagonal to each other on one treatment, after the first half of treatment, the positions are alternated. This ensures that all the walls of the air field structures are covered. This is best for treatment over the sinuses and uterus.
Electrode size: Electrodes should be slightly larger than the part to be treated, to ensure equal distribution of the lines of force, thus resulting to tissue heating throughout the tissues. Small electrodes result in concentration of heat on superficial structures.
Markedly larger electrodes results to ineffective heating, since some electric lines of force will travel through the air and their effects will be lost.
Electrode spacing: this allows electric lines of force to diverge before entering the tissues, thus preventing concentration of heat in superficial structures and
ensures even heating through the part.
Dangers Burns Shock
Fully expose the patient and inspect the skin
Ensure no metal or water around the area you are using Treat on a wooden bed / chair
Nylon clothes must be taken off. Check for sufficient spacing
Warn the patient not to move or touch the leads during treatment No crossing of the leads
PULSED SHORTWAVE DIATHERMY (MEGAPULSE)
This is shortwave at frequency of 27.12 MHz which is pulsed at a rate selected by the therapist. There is pulse frequency range from 15 to 200 Hz.
The pulse duration is constant at 0.4ms and square pulses are used. The advantage of pulsed shortwave diathermy is that a very high intensity of power can be used without a fear of burn. In order to achieve this, the ratio of mean power to the pulse power should be low. By using megapulse, the thermal effect produced by one pulse is of very short duration and is dissipated by circulation before the next pulse occurs.
Biological Effects
The effects of megapulse are the same as those produced by continuous shortwave diathermy, with the exception that no heat production in megapulse. The effects are:
Relief of pain
Stimulation of peripheral circulation Stimulation of wound closure
Indications
Recent sprains Contusions Tendon ruptures Recent haematoma Bursitis
Sinusitis
Contraindications
Unlike continuous shortwave diathermy, very few contraindications apply to megapulse:
Pacemakers High fever
Malignant tumors
Metal implant (not an absolute contra indication, it may draw the current away from the tissues to be treated resulting in ineffective treatment.
Dosage
ULTRASOUND IMPORTANT TERMS:
Ultrasonics is the name given to the technology associated with mechanical vibrations of frequencies above those to which the ear can respond. The upper limit of audibility varies from person to person, but the average is 20 000 Hz. Ultrasonic frequencies range from 20 kHz to 10 GHz.
Longitudinal or compression waves are the to-and-fro oscillations of particles in a medium in the direction of the propagation of the wave, giving rise to alternate compression and rarefaction. The waves can occur in solids, liquids and gases.
Shear or transverse waves generally occur in solids. The particles of the medium oscillate in a direction at right angles to the direction of propagation. Insonation is the art of irradiating the tissue of the body with ultrasound energy.
Piezoelectric effect. When crystals are subjected to pressure or tension, they develop electric charges on opposite crystal surfaces. The conversion of high frequency alternating voltage into mechanical vibration is accomplished by the reversal of the piezoelectric effect.
Acoustic impedance of a material is its characteristic resistance to the propagation of ultrasound. The acoustic impedance is directly proportional to the density of the material and the velocity of ultrasound in it.
Velocity of ultrasound is the rate at which the successive zones of compression travel through a medium. It depends on the compressibility and density of the tissue through which it passes.
Cavitation is the momentary development of cavities within a liquid during the passage through the liquid of the rarefaction (low pressure) phase of an ultrasonic wave.
Transducer or treatment head (sound head) is a crystal inserted between two electrodes. It is the device, which changes energy from one form to another. Transducers are used when energy is available in one form, but required in another.
Phonophoresis: The application of ultrasound with topical drug in order to facilitate transdermal drug delivery.
Power: The amount of acoustic energy per unit time. This is usually expressed in Watts.
Intensity: The power per unit area of the sound head. This is usually expressed in Watts per square centimeter.
Pulsed Ultrasound: Delivery of ultrasound during only a portion of the treatment period. Delivery of ultrasound is pulsed on and off throughout the treatment period.
Continuous ultrasound: Continuous delivery of ultrasound throughout the treatment period.
ULTRASONIC THERAPY
Ultrasound is form of acoustic vibration propagated in the form of longitudinal compression waves at frequencies too high to be heard by human ear. All sound waves are longitudinal mechanical waves. Longitudinal waves cause the particles of a medium to oscillate to and fro in the direction of the propagation of the wave, giving rise to alternate conditions of compression and rarefaction.
Ultrasonic waves are not electromagnetic waves but are mechanical acoustic waves. They range in frequency from 0.75 to 3.5 MHz for physiotherapeutic use.
The human body possesses a characteristic resistance against the propagation of ultrasound. Each tissue in the body has characteristic impedance. It is directly proportional to the velocity of propagation and the density of the tissue. It is important to realize that the flow of ultrasonic energy can occur without a net movement of the medium: the particles simply oscillate about their mean position, and, in this way, energy is transferred through the medium. The propagation velocity is controlled by the density and elasticity of the medium.
Production of ultrasound
The brothers, Pierre and Jacques Curie, discovered that, when a quartz crystal is stressed, a potential difference is produced across its faces. This is called the piezoelectric effect. In 1917 Langevin discovered that by vibrating a quartz crystal with a high frequency alternating current, ultrasound could be produced. All therapeutic ultrasound generators us the reverse piezoelectric effect. Quartz or or ceramic materials are used by manufactures today.
A crystal usually vibrates at a natural frequency, which depends on largely on its thickness. The actual amplitude of movement is small (1 or 2 um). Since
the crystal will vibrate efficiently at only a single frequency, the generator must be tuned to it. The frequency of vibration remains constant for a given generator, but the intensity, in terms of amplitude, can be varied.
Certain crystals such as quartz, tourmaline, and Seignette’s salt, produce electric currents when they are alternately compressed and relaxed in certain directions . Conversely the crystals will contract under the influence of an electric current, and expand when the current is switched off (reverse piezoelectric effect). By continuously varying the direction of the current, the crystal will be made to vibrate and the vibrations produce sound waves.
object is to cut the crystal platelets carefully so the resonance is greatest at the desired frequency. The vibrations are then conducted to the transducer head, which transmits them to the body.
The ultrasonic generator: The therapeutic ultrasonic valve generator produces a high frequency AC from about 0.75 MHz to 3MHz.The resonant frequency of the current is at the same natural frequency as that of the crystal. The high frequency current is applied to the crystal. In front of the crystal lies the transducer head, which is made to vibrate mechanically by the acoustic vibration energy of the crystal.
The basic components of the generator are the power supply, oscillating circuit producing the high frequency current, and the transducer circuit.
The oscillating circuit is similar to that of the valve generators producing short wave diathermy. The capacitance and the inductance of the oscillating circuit are selected to produce an alternating current of the same frequency as the mechanical resonance frequency of the crystal of the transducer. The 50Hz alternating current must be converted to high frequency oscillations of up to 3MHz, and the voltage is increased before application to the transducer crystal. The high frequency generator may be connected directly to the crystal through a cable, or a transformer may be incorporated into the transducer treatment head to couple the crystal to the oscillator, so that the impedances of the crystal and the output circuit are matched.
The transducer or treatment head is a crystal inserted between two electrodes. The crystal or synthetic ceramic is cut according to the electrical axis of the crystal lattice. The crystal translates the electrical oscillations directly into mechanical vibrations which pass through a metal cap into the body through a coupling medium.
the total output of the applicator (power), and then dividing it by the size of the radiating surface of the applicator (area)
PHYSICAL PHENOMENA OF ULTRASOUND
Reflection: When ultrasound passes from one medium to another with different acoustic impendance, certain amount of reflection occurs at the interface between the two media. If the two media have the same characteristic acoustic impedance, there will be no reflection.
Bone-periosteum interface: As periosteum and bone tissue have different acoustic impedances, about 70% of the energy is reflected, and the balance (30%) is absorbed by the bone. The total load on the periosteum is equal to the total incident power plus the reflected power. This causes shear waves to occur around the periosteum. The particles of both media oscillate at right angles to the direction of propagation and, as the wavelength is different in each medium, the particles move in different directions and cause a shear stress at the boundary. This is called a shear stress wave, and is rapidly absorbed at the periosteum. The periosteum is avascular, and no cooling effect occurs,so it quickly heats up and causes a periosteal pain. The patient will soon complain of the heating sensation, because the periosteum is temperature sensitive.
Tissue interface: Reflection also occurs at the tissue air interface. Here air acts as the reflector, and thus ultrasound beam is reflected back to the surface of the tissue area being treated. Excessive heating will occur, causing a heating pain in the skin. This can occur if ultrasound is given to a thin area such as the palm of the hand where ultrasound will go through the tissues and then meet the air on the opposite side. Pain will be felt in the area of the skin opposite the transducer head.
the machine will occur, with no acoustic power going into the patient. The head will be heated rapidly and cause excessive heating of the skin. There is minimal transmission of ultrasound and danger of a burn.
Refraction (deviation): When the angle of incidence is 150,refraction of the
beam is 900 and will run parallel to the interface. Refraction means that the
ultrasonic energy impinges the tissues at one angle and continues at a different angle (angle of refraction). Only for angle of incidence of less than 150 will any energy pass into the tissues. Refraction occurs particularly where
tendon joins bone and leads to concentration of energy. The angle of 150 is
the critical angle concerning the index of refraction. For angle greater than 150
no refracted beam exists, the wave is fully reflected. For angle of incidence of less than 150 there is a reduction of energy going through the tissues. Hence
it is important to hold the transducer head perpendicular to the tissues.
Transmission of ultrasound: Transmission of ultrasound from the transducer head to the site of the lesion.
Attenuation: This is the progressive loss of acoustic power, as ultrasound energy travels through a medium (a measure of the decrease in ultrasound intensity as the ultrasound wave travels through tissue). Attenuation is the result of absorption,reflection,and refraction,with absorption accounting for about one-half of attenuation. The amount of attenuation varies from tissue to tissue. It is worth noting that biological media show attenuation, which is linear and inversely proportional to the frequency. If the frequency is changed from 1 MHz to 3 MHz, the attenuation in muscle changes from 2% to 6% per millimeter. For a frequency of 3 MHz, attenuation is 50% (half value) at 25mm,while at 0.75 MHz half value is at 90mm.
homogeneous tissue model exposed t o an ultrasound field of known intensity. It is generally accepted that absorption of ultrasound energy takes place at molecular level. A series of investigation has established that proteins are the major absorbers of ultrasound among the molecular constituents of soft tissue. The protein in nerve is sensitive to ultrasound. Muscles absorb twice as much as fat. The hemoglobin blood absorbs ultrasound. There is some absorption in structural content of cell membranes. Basically, ultrasound is absorbed at the molecular level, and the absorption coefficients of the tissues are due primarily to the presence of macromolecular tissue contents. Absorption in fluids is determined mainly by viscosity and heat conduction. Absorption of ultrasound is very small, and hence water is a good coupling medium for the transmission of ultrasound.
Micro-massage: This is the alternate compression and relaxation of tissues by the pressure of sound waves and the mechanical reactions of the tissues. Half depth: The depth of tissues at which the ultrasound is half its initial intensity.
Motion and amplitude: The forces of sound pressure will set up in tissues a stress pattern which will produce a reciprocating movement of the cells, in such a manner that there is dispersion and aggregation of the molecules occurring alternately as compression and relaxation. The pressure extremes, maximum and minimum, are separated by one half wavelength. For a frequency of 1 MHz the distance is 0.75 mm. There is a positive maximum pressure and the negative minimum pressure. There are two million changes of direction of movement every second, hence a great difference of pressure occurs over a relatively small distance, and in short period of time.
Oscillation of particles: There is also mechanically caused oscillation off particles in the media.
Cavitation: This is an important feature of high intensity ultrasound, and care must be taken that it does not occur with therapeutic administration. Cavities can be produced during the phase of relaxation or rarefaction. Threshold intensities required to produce cavitation are 1 to 2 w.cm-2 with a
stationery head and above 4 w.cm-2 when a moving applicator is used. Since
there are dissolved gases always present in biological media, gas-filled cavities may be produced in the fluid during the period of rarefaction, when high intensities of ultrasound are given to the tissues. During the phase of compression, the cavities may collapse, creating a high concentration of energy. Mechanical destruction will occur when the gas bubble is large enough to vibrate in resonance with the sound waves or when the cavities collapse.
The ultrasonic field
An ultrasound wave is propagated unidirectionally as a non-uniform beam of acoustic energy. The movement of the particles or molecules in the media occurs parallel to the direction of wave propagation. The sound beams produced by therapeutic application are almost cylindrical in shape. The beaming properties of the sound applicator depend on the presence of a medium that can be compressed, as propagation does not occur in a vacuum. They depend also on the wavelength and diameter of the sound applicator.
Pulsed ultrasound
(Delivery of ultrasound during only a portion of the treatment period. Delivery of ultrasound is pulsed on and off throughout the treatment period.
pulse is rectangular. Heat production is not completely eliminated with a pulse of 1:5.Most equipment has a pulse ratio of either 1:5 or 1:4.Some equipment also provides a ratio of 1:1.
If heat exacerbates pain, then the pulse of 1:5 or 1:4 should be used. If high intensities are being given and the problem of heating of the sound head arises, the ratio of 1:1 can be used in place of continuous ultrasound. It is also useful when there is a lot of reflection from subcutaneous bone, as in epicondylitis, because it will minimize the heat from shear waves, but still give the overall effect of heat and micro massage.
Using pulsed ultrasound for 10 minutes with a ratio of 1:5 means that the patient will only receive 2 minutes of ultrasound.
THE PHYSIOLOGICAL EFFECTS OF ULTRASONIC ENERGY
Micro massage (Mechanical effect)
When ultrasound waves are absorbed in the tissues (remembering that acoustic waves show mechanical properties of compressions and rarefactions of the tissues), there will be immense mechanical forces working in the tissues which cannot be compared with any other physical agent. The alternation of positive and negative pressures at the frequency of the machine causes the micromassage effect of ultrasound. The following biological effects are caused:
-loosening of the microscopic cell structure. -friction which will produce a thermal effect. -oscillation of particles in a fluid medium.
-acceleration of the diffusion processes across the cell membrane -intracellular massage
-breakdown of complex, biomechanically active molecules
-depolymerisation of proteins, especially those which are found in nerve, muscle and collagen cement
reversible decrease of viscosity of intra- and extracellular colloidal substances.
-specific effects on neural and circulatory mechanism. Thermal reactions
Any medium exposed to ultrasound will undergo heating proportional to the energy absorbed, the time of insonated , and the specific frequency of the machine. The friction caused by the micromassage effects of ultrasound causes production of heat in the tissues. As an intact blood supply is generally operating, there is a constant dissipation of any increase of temperature. The advantage is that deep-seated areas can be effectively heated, as there is no loss of energy in the skin and subcutaneous fascia. Owing to the mismatch of impedance at the bone-muscle interface, there is reflection, and some shear waves occur which then cause increased heating effects around a joint or bone. So, if any increase of heat is desired in a muscle or around a joint or bone, ultrasound can effectively produce it.
The maximum effective depth of penetration, and therefore temperature rise in that area will depend on the frequency of the machine, the intensity, and the duration of treatment. Therapeutic dosages of ultrasound, and the dissipation of heat by the circulation reduce any danger of overheating with ultrasound, though care must be taken to consider the patency of circulation and the nervous control of sensation before applying treatment.
To increase the total amount of heat being delivered to the tissues, the duration of ultrasound application and the average ultrasound intensity must be increased. One MHz frequency ultrasound can be used to heat tissues up to 5 cm deep (deep muscle injury), whereas
3 MHz frequency should be used when the goal is to heat tissues only to 1 to 2 cm deep (superficial skin lesion).
Effects on the circulation
The main effects of hyperaemia-vasodilatation, and acceleration of lymphatic flow, are due to the thermal effect of ultrasound. The combination of thermal and micro massage effects produces the histamine-like substance which causes capillary hyperemia.
Non-thermal effects
These effects are the results of the mechanical events produced by ultrasound, including cavitation, micro-streaming, and acoustic streaming. Pulsed ultrasound has been shown to increase intracellular calcium, increase skin and cell membrane permeability, increase mast cell degranulation, increase in chemotactic factor and histamine release, increase in macrophage responsiveness, and increase in the rate of protein synthesis by fibroblasts.
INDICATIONS
Adhesion/Soft tissue shortening
Following trauma, the connective tissue element of fascia, skin, muscle and tendon are predisposed to adhesions. Connective tissue is loose, dense, or organized. It contains reticulin, collagen, and variable elastin fibres in ground substance. The collagen fibril is an aggregation of tropocolagen rods in staggered array. Chemical bonding between the tropocollagen molecules leads increased insolubility and tensile strength. However the process is reversible.
injury within 36 hours. In joints the increase of adhesions and the intracellular substances responds to ultrasound by being converted from the gel to the sol state. It is thought that resorption of adhesions is brought about by both the heating effect of ultrasound and its micro-massage. The quick rise in temperature, which penetrates deeper, and lasts longer at an effective temperature, helps in the process.
Pain and muscle spasm
Pain is the total set of responses an individual makes to a stimulus, which causes or is about to cause tissue damage. If the nervous system is intact, pain can be relieved by various mechanisms, which prevent pain volleys from reaching the supraspinal structures. The interference can be achieved by the micro-massage effect on the nerves, or by raising the temperature of the part. Ultrasound intensities at 1-2 w.cm-2 will reduce the nerve conduction velocities
of the ‘C’ fibres carrying pain.
If pain is due to the accumulation of metabolites causing ischaemia and swelling in the region, ultrasound alters the permeability of cell membrane and aids in accelerating phagocytosis and the absorption of exudates. It also helps to attract the electrophylic pain metabolites and disperse them from the site of the lesion.
Haematoma
Swelling
This is often a complication of trauma (micro or macro-trauma). Effusion of the knee joint, tendinopathy in different muscles, gravitational oedema, and swelling in the tissue spaces following injury to the ankle joint are some of the traumatic swellings that present for physiotherapy treatment. Ultrasound with a dosage of 3 w.cm-2 can alter the semi-permeability of the cell membrane. Ultrasound also causes capillary dilatation which will then help to remove waste products. Lymphatic circulation is also accelerated by ultrasound. Dosages can be calculated depending on the acuteness or chronicity of lesion, and the quality and quantity of exudate.
Overdosage can cause the escapes of the protein plasmas, so care must be taken not to give large intensities.
CONTRA-INDICATIONS
Brain and spinal cord.
Reproductive (Gonads) and abdominal organs.
Pregnant uterus.
Deep venous thrombosis or arterial disease.
Haemophilia.
Tumours/Malignancies and precancerous lesions.
Tuberculosis of lungs or bone.
Acute infection or sepsis
Patient having deep X-ray therapy or radium isotopes.
Epiphyseal plates
Cardiac area in advanced heart disease.
DANGERS
Burns:The main cause of burns are; Overdosage
Too slow a movement of the transducer head over the lesion
Right angle application of the transducer head over the lesion is not maintained and
the there is occurrence of shear waves which produces heat. Insufficient couplant.
Entrapped air in the couplant
Irregular bony surface which negates absolute contact with surface.
Shock
Deterioration of the cable connection to a movable angle transducer head could cause a shock.
INTERFERENTIAL THERAPY
A form of electrical treatment which uses two medium frequency currents to produce a low frequency effect deep inside the tissues.
One current is kept constant and the other varied e.g. 4000Hz and 4050 Hz or 4000Hz and 4100Hz. A vibration occurs where the currents cross and this is called the interference effect. The combined current/resultant current has a beat frequency which is a difference between the two frequencies (50Hz and 100Hz respectively from the example above.)
By varying the frequency of the one current in relation to the other, it is possible to produce a range of beat frequencies deep in the tissue. This is called the frequency swing or frequency sweep.
A rhythmical range is achieved by varying the frequency in the second circuit by a period of 5 – 10 seconds.
A machine can be set to automatically change one of the medium frequency currents to give a continuous varying beat frequency. The variation can be made between specified upper and lower limits e.g. 1 -10Hz. The time taken for each swing/sweep can be controlled on some machines.
PHYSIOLOGICAL EFFECTS These depend on:
The frequency range
Use of rhythmic or constant mode Intensity of current
Accuracy of electrode placement
FREQUENCY RANGES
100Hz Constant Analgesic effect
Vasodilation resulting in pain relief by removal of pain metabolites and mobilization of any exudates.
1 to 100 Hz rhythmic
Gives a stimulating and analgesic effect. Rhythmic modulation produces more stimulating fine vibrations of ions and facilitates ion movement in the cells. This effect produces hyperaemia and increased cellular activity with increased
permeability of cell membrane. This increases venous and lymphatic drainage. It is useful for the relief of oedema and facilitation of healing process.
1 – 10Hz Constant
Stimulation of motor nerves (normally rhythmic contraction and relaxation)
90 – 100Hz Rhythmic Analgesic effect
More effective for treatment of neurogenic pain
Has less adaptation/ACCOMMODATION THAN 100Hz constant
1 – 10Hz Rhythmic
Stimulation of motor nerves
INDICATIONS 1. PAIN RELIEF
For the treatment of acute pain, post-traumatic and chronic pain with or without oedema. More effective for neurogenic pain e.g. post-herpetic neuralgia, causalgia and phantom limb pain.
2. MUSCLE SPASM 3. OEDEMA
Aids in resorption of exudates. 4. HAEMATOMA
First 24hrs - may be used with ice to aid in its resolution - after 24 hrs, may be used with ultra sound 5. CHRONIC LIGAMENTOUS LESION (Sprains/Strains)
For relieving pain and accelerating the healing process. 6. STRESS INCONTINENCE
For stimulating weak pelvic floor muscle. Special electrode (vaginal or rectal) may be used.
7. DELAYED UNION AND STUDECK’S ATROPHY
8. POST TRAUMATIC AND POST INFECTIVE DISORDERS Contusions, sprains
9. INFLAMMATORY CONDITIONS
E.g. Tendinitis, bursists, pelvic inflammatory disease (PID)
10. CIRCULATORY DISTURBANCES DVT should be excluded.
Fever
Haemorrhagic conditions DVT
Over pregnant uterus Arterial disease Neoplasm
Large open wounds Dermatological conditions Cardiac pacemakers TB
Unreliable patients
DANGERS BURNS
Bare electrode touching skin Pads not moist enough
Skin currents if electrodes are too close to one another HAEMATOMA
Due to high vacuum pressure when suction cups are used
POOR RESULTS
Due to incorrect choice of frequencies Poor positioning of electrodes
Poor balancing of circuit (in a quadripolar arrangement)
ADVANTAGES
1. Current can be localized to specific areas by careful electrode placement
3. Metal implant not a contra indication 4. Poor skin sensation not a contra indication
5. Interferential therapy can also be effectively used in the pain resulting from tumours as long as the electrodes are not applied over the tumours.
APPLICATION
Establish the history from the patient. Check for contra-indications.
Inspect part for: - increase in temperature - swelling
- cuts - infections
TEST SENSATION
Wash the area to reduce skin resistance. Insulate any skin lesions.
Depending on the site of the lesion, decide on whether you arte going to use a bipolar or quadripolar method.
NB: In a bipolar method the current is premodulated i.e. the interference effect is generated within the machine.
The disadvantage of this system is that the lesion will only be treated for part of the time. It should therefore only be reserved for cases where the lesion cannot be accurately localized.
1. CHOICE OF ELECTRODES
a) Size
Depends on the size of the lesion
b) Type
Depends on the location of the lesion. If the area is flat and easy to reach, flat electrodes may be used, and if the area is irregular or positioned such that it would be difficult to strap the flat electrodes, suction electrodes may be used.
2. POSITIONING OF ELECTRODES
The electrodes should be positioned properly and secured in place using velcro straps, suction cups or bandages.
a) Bipolar technique
The area to be tested should always be between electrodes. The electrodes may be placed opposite to one
another.
On the same aspect of the part.
(NB – when placing the electrodes on the same aspect, they should not be placed too close together – to avoid skin current compensation)
After the lesion has been localized, the electrodes in each circuit are placed diagonally opposite one another such that the two circuits meet directly over the lesion.
NB: The electrodes must be covered with pads. The pads should be moist not dripping wet. When using suction cups, make sure that the suction pressure is not too high.
3. CHOCE OF FREQUENCY AND MODE
The choice of frequency depends on the desired effect (refer to physiological effects)
MODE
(Only applicable when using rhythmic frequencies)
1/1 - aggressive - for chronic and subacute conditions 1/6 - milder - for acute conditions
6/6 - mildest - for acute and painful conditions
4. CHOOSE THE INTENSITY
The intensity is determined by what the patient perceives
LOW DOSES not noticeable MEDIUM DOSES Just perceptible
HIGH DOSES Clearly experienced by patients as vigorous, pleasant sensation
VERY HIGH DOSES
Strong vigorous, almost unpleasant sensation
Generally medium doses are used
HIGH DOSES - For tenacious exudates - For muscle stimulation
NB: The intensity has to be adjusted during treatment to counteract accommodation. Liase with patient.
Constant frequency accommodation faster than rhythmic frequencies.
5. DURATION OF TREATMENT
Treatment lasts on average 10 minutes
6. FREQUENCY OF TREATMENT
]
ULTRAVIOLET LIGHT (UVL)
Ultraviolet (UV) rays are electromagnetic waves lying between visible and X-rays in the electromagnetic spectrum. They are subdivided into UVA, UVB and UVC.
UVA - 315 – 400nm (290 – 390) UVB - 280 – 315nm (180 – 290) UVC - Below 280nm
The natural source of UV rays is the sun but for therapeutic purpose, they are produced by mercury vapour lamps. The lamp consists of a quartz burner evacuated of air and containing argon gas and mercury under reduced pressures. The current vaporizes the mercury, and the passage of electrons through the vapor establishes the UV rays. All UV generators also produce visible light and Infra - red (IR) rays. Because of the IR rays, the quartz burner heats up to 60o to several hundred degrees Celsius. It is therefore necessary to
incorporate a cooling device into the lamp particularly if it is going to be used close to the patient or in contact. Devices commonly used include air cooling and water cooling (using a water jacket surrounding the burner with continually circulating water).
AIR – COOLED LAMPS (ALPINE SUN)
The lamp is recommended for the generalized skin conditions e.g. acne and psoriasis.
WATER – COOLED LAMPS(Kromayer)
UVA and UVB rays are produced.
The lamps are designed for the treatment of localized lesions eg .pressure sores and ulcers and with the attachment of applicators, for the treatment of sinuses FLUORESCENT TUBES eg Theraktin lamp
Consist of a number fluorescent tubes incorporated in to a semi-circular burner. The wavelengths produced are of the UVA range.
As UV rays are electromagnetic waves, they will also be governed by the same laws
as other ray ie. Reflection, refraction, penetration absorption and the law of inverse squares.
PHYSIOLOGICAL EFFECTS Divide into two:
- Local effects - General effects
LOCAL EFFECTS
ERYTHEMA –reddening of the skin
It is the first observable effect of UV irradiation. It is not visible for at least one hour and reaches its maximum at +- twenty four hours.
It is a result of the inflammatory reactions stimulate by UV irradiation. The rays cause irritation and degenerative changes in the epidermis and this results in the release of histamine- like substances resulting in triple reactions – dilatation of capillaries and arterioles – exudation of fluid into the tissues.
Pigmentation follows erythema. The amount of pigmentation varies with the amount of erythema , with low intensity , erythema may be visible after repeated exposure with rays .
Pigmentation is due to increased deposition of the pigment melanin formed within the basal skin layer by the melanocytes . UV is said to accelerate the
productionof melanin by stimulating the production of the enzyme tyrosinase in the melanoblasts.
DESQUAMATION/ PEELING
Casting off the cells which have been destroyed by UV rays. The extent of desquamation is proportional to the intensity of the erythema . With mild erythema, desquamation may be seen after repeated exposure to UV rays.
GROWTH OF EPITHELIAL CELLS
Growth of epithelial cells is increased as part of the repair process which follows the erythema.
The cells of the basal cell layer proliferate to replace the cells that were destroyed by UV rays. Thickening of the epidermis occurs as a result.
ANTIBIOTIC EFFECTS
The destructive effects of UV radiation include the destruction of viruses, bacteria and small organisms on the skin.
The effect is primarily by short rays – UVB.
GENERAL EFFECTS Formation of vitamin D
Vit D formation is accelerated by UV irradiation. Vit D is required to assist in the absorption of calcium and phosphorus from the intestine into the blood stream.
The resistance of the body to infection is enhanced especially if general
irradiation of UVA is given. This is said to be a result of stimulation of the reticulo-endothelial system, the cells of which ingest the bacteria and produce antibodies against the bacteria and toxins.
Variations in responses to UV rays
There is a wide INDIVIDUAL variation to UV rays. The variations are attributed to:
-variation in skin
-degree of pigmentation -? Age of subject
-varies from one area of the body to another -wet skin absorbs more UV rays than dry skin
Natural protection against UV rays
With repeated exposure to UV, the sensitive of the skin to UV decreases. Thickening of the skin – stratum cornea – following UV irradiation is a major factor
responsible for development of this protection.
THERAPEUTIC EFFECTS
Local effects are generally required for these purposes:
ERYTHEMA Useful in conditions where increase in circulation is required. Also where infection is present e.g. acne, infected wound. Where skin condition is poor e.g. in pressure sores and ulcers.
PIGMENTATION Not required for therapeutic purposes.
GROWTH OF
EPITHELIAL CELLS
Major effect used in the treatment of open wounds eg. pressure sores, ulcers, slow healing surgical incisions and dermatological conditions e.g. acne. ANTIBIOTIC EFFECTS Required for the treatment of infective conditions
eg. acne, ulcers and pressure sores.
DOSAGES
UV dosages are graded according to the level of the erythema, this depends on the length of exposure to UV.
NB: The reactions are based on the reaction observed on normal skin.
MINIMAL ERYTHEMA DOSE (MED)
Mild erythema which appears after 6 – 8 hours and which is just visible after 24 hours.
E1 - First degree Erythema dose
Mild erythema, appears after 6 – 8 hours. Disappears just before 24 hours elapses.
Fine desquamation occurs after repeated exposures.
E2 – Second degree Erythema dose
Appears within 4 – 6 hours. Disappears within 48 hours.
E3 – Third degree Erythema dose
Marked erythema which appears within 2 – 4 hours and lasts for 72 - 96 hours. Resembles severe sunburn and is associated with oedema and tenderness. It is followed by marked pigmentation and desquamation, the skin peels off in sheets or flakes.
E4 – Fourth degree Erythema dose
E4 may be given to areas that have been denuded of skin e.g. open and septic
pressure sores.
CALCULATION OF DOSAGE
The basis for the calculation of the dosage is the E1 which is determined for each
INDIVIDUAL by the skin test. All doses can be calculated from it.
The two significant levels of measurement are:
a) The length of time (usually measured in seconds). b) The distance from the source.
Five levels usually used
E1 - calculate from skin test
SUB E - 1/ 2 E1
E2 - 21/2 x E1
E3 - 5 x E1
E4 - 10 x E1
Progression
To achieve the same effects, each subsequent dose applied to normal skin has got to be progressed.
E1 = 25% of preceding dose
E2 = 50% of preceding dose
E4 is not applied to normal skin. While skin develops resistance to UV, non- skin
areas do not, therefore it is not necessary to progress the dosage when treating an area not covered by skin. These areas can be treated with the same dose on successive days.
Example
The E1 of the patient is 10s at a distance of 300mm. Calculate the E2 and the
first progression of the dose (P1, E2).
i) E2 = 21/2 x E1
= 21/
2 x 10s
= 5/2 x 10 = 25s
P1E2 = E2 + 50% x E2
= 25s + 0.5 x 25s = 25s +12.5s = 37,5s at 300mm
It is very important to specify the distance at which your treatment will be given especially when using the air – cooled lamp.
KROMAYER
Burner with water jacket surrounding it. There is a distance of 25mm between the burner and the outer window of the treatment head. The distance is not included in the description of the dose because it is a constant but is used during
In the air – cooled lamps, the distance is measured from the burner to the patient.
DOSAGE LEVELS
E1 - can be used to irradiate the whole body.
E2 - 20% of the body.
E3 - 250cm2 of normal skin.
E4 - Given to non – skin area and the size of the area is not important.
FREQUENCY OF TREATMENT
Depends on the level of erythema produced. E1 - may be given daily.
E2 - every second day.
E3 - every third day.
E4 - when treating non-skin areas e.g. pressure sores or ulcers, the dose may
be repeated daily.
EFFECTS OF DESQUAMATION ON DOSAGE
Desquamation leads to loss of the natural protection developed by irradiation with UV rays and exposes the skin. The successive dose should therefore de reduced. After desquamation treatment is reduced to the original dose eg. If patient was receiving a P6E1 dose, it should be reduced to E1.
INDICATIONS
UV is used for the treatment of dermatological conditions as well as infected and uninfected skin lesions.
a) Acne
Aims:- Promote desquamation, to open blocked pores.
- Erythema to improve skin condition.
- Stimulation of growth of epithelium.
Ideal dose E3 but an E2 is given to the face chest and neck. An E1 dose may also
be used. Air- cooled lamp is generally used. b) Psoriasis
A chronic, non infective skin disease characterized by scaly plaques on the skin. The cause is unknown and largely familial. In some patients this can be triggered by physical and emotional stress. In some patients a reaction to drugs eg. ,latrogenic drugs ie. Lithium, anti-malaria, beriz- blockers.
Aims: - To reduce the DNA synthesis in the cells of the skin with resultant decrease in proliferation of the cells which cause the silvery plaques.
- To facilitate an increase in circulation and improve skin condition.
Two regimes usually used A. Leeds Regime
Coal tar bath with gentle rubbing of the skin to loosed and remove the psoriatic plaques, then UV using E1. After irradiation, dithranol cream is
applied to the psoriatic plaques. B. Photochemotherapy
Patient given a sensitizing drug and a skin test or treatment performed 21/ 2
hours thereafter.
c) Threatening Pressure sore
UV is given to improve the skin condition and stimulate growth of epithelial cells. E1 dose progressed daily may be used.
d) Non infected open wound UV is used to promote healing.
Aim: To stimulate growth of granulation tissue and prevent infection by destruction of the surface organisms.
e) Infected open wound
UV destroys slough that forms on the surface of the wound and improve granulation through increased circulation.
1. Acute dermatological conditions. 2. Hypersensitivity to sunlight.
3. Febrile conditions (Increased temperature).
4. Within 3 months after Deep X- ray therapy (DXT)- this will increase sensitivity.
5. Immediately after Infrared Therapy, increases erythema reaction which will increase UV Effects.
6. Photoallergy
7. TB and tumors, these may be aggravated by the exposure.
DANGERS 1. Electric shock
2. Damage to the eyes ie. conjunctivitis, iritis, cataracts.
3. Overdose, may result in a UV burn because of inaccurate dosage calculation.
4. Sensitising drugs, these will make the patient more sensitive to UV and an overdose reaction may appear.
SKIN TEST PROCEDURE
The lamp usually has an E1 which is taken from average population. This is
done with consideration of the patient’s normal reaction to sunlight. Check if the patient is taking any sensitizing drugs.
Cut out 3 different shapes of lint material and apply the material to a suitable area. Never do the test on the face.
Position the lamp and measure distance from theburner accurately. The rays must be perpendicular to the skin.
Irradiate all areas. Start irradiating with the E1 of the machine and
progress by 1minute each exposure ie. if the E1 is 2min, start with 2min
Instruct the patient to inspect the area +- 6- 8 hours after exposure and must record the time each appeared and disappeared.
FOR ACCURACY ALWAYS RECORD 1. Date
2. Time
3. Anatomical location 4. The lamp used and its E1
5. The distance of the lamp from patient 6. Time of each expose
7. Physiotherapist’s signature
Patient should be seen 24 hours after skin test. The E1 of the patient will be
determined by that area which became erythematous at 6 – 8 hours and disappeared at 24 hours.
Precautions
1. Wear goggles at all times
LIGHT AMPLIFICATION BY STIMULATED EMISSION OF IRRADIATION (LASER)
Laser is an acronym for light amplification by stimulated emission of radiation. This refers to stimulation of photons striking excited atoms to increase or amplify the number of photons produced by the lasing medium.
Laser was discovered in 1960 and has gained popularity in recent years both in surgery and in therapeutics.
There are two types of laser, the high power or hot laser and the low power or cold laser. The type of laser produced depends on the ionizing substance eg.
CO2 laser – hot He-Ne laser – cold
a) High power laser/ hot laser
In this type of laser, the light energy is converted into heat when absorbed by the tissues. The amount of heat produced may result in reversible or
irreversible tissue changes. This type of laser is used in surgery for cutting or destruction of tissue.
b) Low power laser/ cold laser/ soft laser
Its major function is stimulation, and it is this type that is used for price
detection in grocery shops and for physiotherapeutic purposes, the treatment is often called low level laser therapy (LLLT).
PRODUCTION OF LASER
Laser is produced inside a resonator, which is a sealed chamber containing the active substance. This substance, which is called the lasing medium may be a liquid e.g. Fluorescent dye, a solid e.g. r
