OBJECTIVE Without reference, identify at least four out of six principles pertaining to the application of ultrasonic therapy. Ultrasonic therapy- is the therapeutic application of a form of acoustic vibration at frequencies too high to be heard by the human ear. The sound waves spread through the tissues, where they are absorbed and converted into hear. This type of heating is by conversion. Conversion is just thatheat transferred when energy penetrates into deep layers of the body tissue where it is converted into heat. The following features of ultrasound are to be considered: Acoustic vibrations below 20,000 Hz are called sound Acoustic vibrations above 20,000 Hz are called ultrasound. This frequency is inaudible. The physics of ultrasound is the same as audible sound, except for the differences in frequency. For therapeutic purposes, the ultrasound frequencies range from 0.8 to 1 megahertz (MHz) There are three circuits generally found in all therapeutic ultrasound devices: Power supply circuit- transforms the alternating wall current into a high voltage DC, and a lowvoltage AC for the oscillating circuit. The power supply circuit is constructed so the 220V, 50Hz AC line current does not noticeably modify the steady output of the power supply circuit. Oscillating circuit- Produces an AC having a high frequency of about 0.8 to 1 MHz. The frequency of the oscillating circuit equals the mechanical frequency of the crystal in the transducer. It is possible to adjust the frequency of this AC by tuning unless the manufacturer installed a device for controlling the oscillating frequency. The oscillating circuit is also referred to as the generator. Transducer circuit- is where the high-frequency AC produced by the oscillating circuit is supplied to a crystal. This crystal converts the electrical current into mechanical (acoustic) vibrations. This conversion happens by a reversal of the piezoelectric effect. The transducer circuit is also known as the transducer, applicator, or sound head, and is attached to the machine by a coaxial cable. This coaxial cable transmits the high-frequency AC from the generator to the crystal housed within the sound head (transducer circuit) Clinical application There are two types of techniques for administering therapeutic ultrasound to the patient. • Direct contact, a viscous fluid is used as a coupling agent between the applicator and skin. Mineral oil or an aqueous gel are the most frequently used coupling agents. The direct contact method is used to apply ultrasonic energy to areas of the body that are relatively smooth and have few bony prominences. Indirect method utilizes H2O as the coupling agent between the applicator and skin. The applicator is held ½ to 1 inch away from the skin with the transducer and body part submerged in H2O. This is the ideal way for applying ultrasonic energy to irregular surfaces and bony prominences. During ultrasonic therapy treatment, clinically we cannot measure the parameters that determine the biologic response to ultrasound: temperature obtained in the tissues, duration of the temperature elevation, and rate of temperature rise within the tissues. We can however, measure the amount of energy (intensity) expressed in terms of watts per centimeter squared (W/CM2), which refers to the average intensity of the field. On most ultrasound machines, this information is obtained from the meter on the panel. The intensities of ultrasound for therapeutic purposes range from 0.5 to 4 W/CM2. For most applications, the duration varies from 3 to 10 minutes for each field in the area of application. Ultrasound is an effective deep-heating agent. It is possible to produce higher temperatures in bone than either the fatty or muscular tissues even when the bone is covered by more than 6 centimeter (CM) of soft tissue. Unlike the other thermal treatments, ultrasound can be used safely in the presence of metal implants. The metal implants have a very high thermal conductivity so the heat is removed from the area more rapidly than it is absorbed. Ultrasound is applied to heat joints covered with a thick layer of soft tissue, such as the hip-joint. Other modalities, even shortwave diathermy, cannot heat these deeper structures to a therapeutic level producing results comparable to ultrasound. Ultrasound selectively heats denser structures permitting an increase in their extensibility. For this reason, it is very effective when applied to a joint with limited mobility. Three denser structures that this can be applied to are: joint capsules, ligaments, and tendons. Ultrasound may also be used as a heating agent over nerves. The heating effect may reduce the irritability of the nerve, and relieve the pain and spasm effects of the nerve root irritation. Physiological effects Most of the physiological effects that are of potential therapeutic value are a result of the increase in tissue temperature resulting from the absorption of ultrasonic energy. The following table list the local and systemic effects that occur: Some precautions you must be aware of when working around ultrasound equipment are: Do not apply ultrasound to the eyes, areas with decreased blood flow, malignancies, a pregnant uterus, or to a patient with predisposition to hemorrhagic disease. Apply ultrasound with caution to areas of sensory impairment. Observe the patient during treatment for signs of possible tissue damage due to heat. If for any reason the unit does not appear to be operating properly, a simple test to check for normal output from the transducer is: Wrap a piece of 1-inch adhesive or masking tape around the front edge of the transducer to form a cup With the transducer head in the inverted and vertical position, pour approximately ¼” water into the cup formed by the tape Operate the machine in the normal manner, slowly increasing the intensity control from zero to maximum output As the intensity is advanced, the water forms a small cone; at full output, it forms a sharp peak and shows violent agitation The test can also be performed in a tank of water of sufficient depth to accommodate the transducer, with the transducer free in a horizontal position about ¼” below the surface If you discover you have little or no activity shown by the preceding tests, this indicates improper unit operation, or possible transducer cable or head problems The transducer assembly and cable can be spotchecked rather quickly by removing the whole assembly and taking am X-ray of it to detect possible breaks in the cable wiring. Another method, depending on availability, is to swap out the transducer and cable assembly with another unit manufactured by the same company. Emphasis here in on the word “same;” never attempt to use another manufacturer’s parts on the unit you are servicing. Severe damage may occur to the unit or component parts being trouble shot, resulting in two units being unserviceable instead of one. Also, there is a possibility of creating an electrical shock hazard endangering you, the operator, or the patient. Physical therapy uses a wide variety of therapeutic equipment; this lesson discusses hydrotherapy units. If you look at the word “hydrotherapy,” it tells you exactly what type of equipment this is— H2O (water) therapy specifically, we address the principles and applications of the whirlpool bath A whirlpool bath is a vessel in which H20 at a given temperature is kept in constant agitation and permits immersion of an extremity. Principles of operation - The whirlpool bath combines heat with mechanical action to stimulate circulation and relax muscles. There are three major types of whirlpool baths. ◦ The arm bath, which is a small tank mounted on a pedestal. ◦ The leg bath, which is a larger tank mounted on the floor. ◦ The body bath, also floor mounted. These are the largest of the three types. Since the only difference in the three types is their physical size, we will discuss them in generic terms. Whirlpool baths are constructed in three main components: the tank, turbine ejector, and the aerator assembly. ◦ The tank is fabricated of heavy-gauge stainless steel with a satin finish inside and out. It contains a quick-acting thermometer to indicate H20 temperature. Drainage of the tank is accomplished by a combination drain and overflow valve. The turbine ejector is constructed to move in all directions. It has four main components: turbine housing assembly, suspension bracket, aerator tube assembly, and electric motor. The turbine ejector bracket is attached to a raising and lowering rod attached to the outside of the tank. The aerator tube assembly contains a butterfly valve to regulate the volume of air passing through the tube. The motor is a vertically mounted, inductive-type unit protected by a manually reset thermal overload switch. It contains permanently lubricated, sealed bearings. The whirlpool bath must have a means to regulate the H20 temperature delivered to the patient; this is done by the using a thermostatic mixing valve. ◦ the mixing assembly is composed of a thermostatic mixing valve, hot H20 inlet, cold H20 inlet, volume control valve, and vacuum breaker. ◦ The normal four positions obtained from this valve are shut or off, cold, warm, and hot. ◦ The normal temperature range for the average arm and leg whirlpools is approximately 100°F to 110°F. ◦ The approximate range for a body bath is between 90° to 100°F. ◦ These ranges vary depending on the patient’s disability and sensitivity, and the physical therapist’s preference. Clinical application ◦ Whirlpools are used therapeutically to heat large areas of the body at one time, at a constant temperature, and attain a uniform coverage. ◦ They also massage body tissues by the moving H20. ◦ Whirlpools are widely accepted and used in cleaning and debridement of open wounds and severe burns. ◦ Often, a bacterial agent is added to the bath to take advantage of whirlpool agitation. ◦ The whirlpool is also used to increase body circulation by alternating the hot and cold H20 of the bath. ◦ The buoyancy obtained in the whirlpool bath helps the therapists with exercise routines. ◦ As you can see, anyone having generalized joint involvement, such as arthritis, is a prime candidate for the whirlpool bath. ◦ Patients suffering from post-cast stiffness can benefit, as well as patients with traumatic or inflammatory conditions, such as sprains, strains, and contusions. Physiological effects ◦ Heated H2O in a whirlpool bath produces all the physiological effects most superficial or local heat applications produce. The following are effects of this heated H20: Circulation General peripheral vasodilation Lymph circulation and drainage increased Cardiac output and pulse rate increased Body temperature increased Respiration increased Metabolism increased Profuse perspiration Muscle relaxation Sedation of nerve endings ◦ There are two specific problems that can be aggravated by whirlpool treatment to patients with the specific ailments: Advanced cardiac conditions — further strain on the circulatory system could result Hyperthyroidism — an already high patient metabolism may be further increased Operational inspection ◦ Observe safety at all times when working around whirlpool equipment. It doesn’t matter what manufacturer’s brand you are dealing with because they all have the same general characteristics, including the use of H2O and electricity—a fatal combination if appropriate safeguards are not observed. ◦ Even though a whirlpool bath may seem simple enough, familiarize yourself with the manufacturer’s literature before you perform an operational inspection. ◦ Next, review your work order records to ensure all basic areas of concern noted in the past are examined separately. ◦ After you check the unit over and you are sure everything is in order, it is time for an operational inspection. ◦ Before you turn the unit on, there is a word of caution: do not attempt to start the turbine ejector until the H2O level in the tank is well above the housing at its lower end. This precaution extends the life of the turbine ejector’s leather bearing, which is lubricated by the H2O; it must be submerged or it will “freeze up.” ◦ Start the motor by turning the insulated toggle switch to ON. ◦ Direct the direction of the H20 jet by rotating to the right or left, or by raising or lowering the turbine ejector assembly. The unit is secured by a friction lock and locking pin. ◦ Proceed to check the turbine ejector in combination with the aerator, which mechanically agitates the H20. The impeller blades at the bottom of the ejector should force jet of H20 across the bottom of the tank. ◦ To verify the fan on the motor is functioning properly, there should be a steady flow of air out the butterfly valve and into the tank in front of the jet from the ejector. ◦ If all of these steps prove positive, an operational inspection of the thermostatic mixing valve is next. ◦ With the thermostatic mixing valve handle set to the HOT position and the volume control valve open, the mixing valve should supply hot H20 at a temperature of approximately 115°F. ◦ Now, turn off the cold H20 supply to test the hot H20 shutoff. ◦ A properly operating mixer shuts off the hot H20 almost instantly. ◦ Failure to do so could indicate: Dirt between the hot seat in the liner and piston, preventing it from closing; it must be cleaned. A stuck piston that cannot move because of scale or foreign matter in the H20; the unit must be cleaned. A malfunctioning thermostat; it must be replaced. ◦ Now that you have checked the hot H20 shutoff, turn off the hot H2O and check the cold H20 by opening the cold supply to the mixer. This is accomplished by moving the mixing valve handle to the COLD position. ◦ A full volume of cold H2O should be supplied by the mixer. ◦ Now, move the handle back to the HOT position as far as possible. ◦ The flow of cold H20 should decrease to a very small flow. ◦ Failure to do this indicates: A stuck piston; it needs cleaning The piston spring has lost strength and needs replacing. ◦ If you find the mixing valve does need to be disassembled and cleaned, refer to the service manual to ensure components are taken off in the proper sequence or returned properly upon reassembly. ◦ Check the accuracy of the dial thermometer in the tank by using a calibrated digital temperature system or comparable calibrated mercury thermometer. ◦ The procedure is simple to accomplish: Fill the tank at a particular temperature setting Immerse your calibrated thermometer next to your tank thermometer Wait 1 or 2 minutes for the thermometer to stabilize Compare the reading with the tank thermometer. ◦ If you find more than a 2°F difference, this usually indicates thermometer replacement is necessary. ◦ Refer to the manufacturer’s service manual for possible adjustments on some models.