Electrotherapy Lecture 6 PDF

 Interferential Stimulation (IFS) ‫ببساطة جدا فكرة عمله عباره عن اننا بنجيب تياريين بترددات عالية عشان يوصلوا الجزاء عميقه اكتر في الجسم ولكن‬ ‫مبيكنوش متساويين بيكون تردد تيار اكبر من التاني عشان لما يوصلو في الجسم كل تيار بيلغي التاني فلي بيتبقا ويستفاد‬ ‫ طب اح...

 Interferential Stimulation (IFS) ‫ببساطة جدا فكرة عمله عباره عن اننا بنجيب تياريين بترددات عالية عشان يوصلوا الجزاء عميقه اكتر في الجسم ولكن‬ ‫مبيكنوش متساويين بيكون تردد تيار اكبر من التاني عشان لما يوصلو في الجسم كل تيار بيلغي التاني فلي بيتبقا ويستفاد‬ ‫ طب احنا ليه بنعمل اللفه الطويلة ده ؟ عشان كده احنا‬, ‫منه الجسم الفرق الي بينهم عشان كده الزم ميكنوش متساويين‬ ‫ أوال وصلنا لمناطق عميقه فستفدنا من الترددات العالية وثانيا لما وصلنا للمنطقه الي عايزة‬,‫بنضرب عصفورين بحجر‬ ‫تتعالج استخدمنه فرق الترددات الي اتبقي في االخر وبيكون تردد منخفض الي احنا عايزينه‬ Introduction -Frequency is used to describe the number of electrical pulses (or cycles) delivered to the tissues. -Low-frequency currents, less than 1000 cycles or pulses per second (biological effects) -medium-frequency currents range from 1000 to 100,000 cps -high-frequency currents, greater than 100,000 cps (heating effects) -There is an inverse relationship between the frequency of an electrical current and the capacitive resistance offered by the tissues. F capacitive resistance --------------------------------------------------------------------------------------------------------------------- Interferential Stimulation -Interferential stimulation (IFS) units generate two Alternating Currents on two separate channels. One channel produces a constant frequency sine wave (4000 to 5000 Hz), and the other channel produces a sine wave with a variable frequency. The two currents meet in the body to produce an interference wave having a frequency of 1 to 299 Hz. -Traditionally, sinusoidal alternating current has been used for IFC, but some devices now use square, rectangular, or even triangular alternating current. -The medium frequency carrier currents penetrate the deeper tissues with very little resistance with relatively little patient discomfort. --------------------------------------------------------------------------------------------------------------------- Interferential -Interferential therapy utilizes two medium frequency currents which pass through the tissues simultaneously. They are set up so that their paths cross. -Medium frequency A + Medium frequency B = low (therapeutic) frequency C -------------------------------------------------------------------------------------------------------------------- Production of interferential current -One current is normally of fixed frequency, for example at 4000 Hz, and the other current is adjustable )‫ قابل للتعديل (متغير‬, for example between 4000 and 4200 Hz. -Two currents summate or cancel each other out in a predictable manner, producing the resultant amplitude-modulated ‘interferential current’. --------------------------------------------------------------------------------------------------------------------- Principle of interferential therapy -The basic principle of the interferential therapy (IF) is to utilize the strong physiological effects of the low frequency electrical stimulation of muscle and nerve tissues at sufficient depth, without the associated painful and somewhat unpleasant side effects of such stimulation. --------------------------------------------------------------------------------------------------------------------- Frequency and skin resistance -The lower the stimulation frequency, the greater the resistance to the passage of the current, so more discomfort is experienced. - The skin impedance at 50 Hz is approximately 3200 ohms, whilst at 4000 Hz it is reduced to approximately 40 ohms --------------------------------------------------------------------------------------------------------------------- IFC and Skin impedance -The suggested decrease in skin impedance noted with KHz frequency current is not specific to the frequency but rather to the short pulse duration necessarily associated with KHz frequencies. Skin impedance is directly related to pulse duration, not frequency, so that at very short pulse durations, impedance is reduced. Pulse duration skin impedance --------------------------------------------------------------------------------------------------------------------- Carrier frequency and beat frequency -The currents are maximally in or out of phase at a rate equal to the difference between frequencies of the currents interfered. -For example, interference of a 4,000-Hz and a 4,100-Hz: Carrier frequency (4,000 Hz) Beat frequency (4,100 – 4,000 = 100 Hz) -The beat frequency reflects the therapeutic frequency—that is, the frequency that elicits the therapeutic effect. --------------------------------------------------------------------------------------------------------------------- The beat frequency -The physiological effects elicited by IFC are based on the beat frequency, not the frequencies of the input currents or current shape (i.e., sinusoidal or other). -On most contemporary devices, the clinician selects the beat frequency while the carrier frequency is prefixed at 4,000 Hz. Still other devices permit the clinician to adjust the carrier frequency within 1,000 to 5,000 Hz. --------------------------------------------------------------------------------------------------------------------- Sweep frequency -Some IFC devices allow the frequencies of the input currents to be modulated, resulting in a modulated beat frequency within definite range. This effect is termed sweep but is not available on all devices. -Sweep is either a linear or peak-to-peak sweep. -With linear sweep, the beat frequency is modulated continuously from a maximum to a minimum frequency. ‫التغير من اكبر تردد الي اصغر تردد مع الترددات الي بينهم‬ -a peak to peak sweep results in the alteration of the beat frequency between only the maximum and minimum. ‫التغير من اكبر تردد الي اصغر تردد فقط‬ sweep ‫التغير في الزمن الي بيحصل‬ ‫اثناء‬temporal characteristics of the sweep or the timing of the sweep. -Swing represents the ----------------------------------------------------------------------------------------------------------------------------------------------------- Swing -Swing is used to denote the temporal characteristics of the sweep pattern with “^” used to denote a linear or continuous sweep and “∫” used to denote peak-to-peak sweep. -for example, a 2^2 sweep from 100 to 10 Hz will decrease continuously from 100 Hz to 10 Hz over 2 seconds and then increase continuously and linearly over the next 2 seconds. In contrast, a 2∫2 sweep from 100 to 10 Hz denotes that the beat frequency remained at 100 Hz for 2 seconds before switching to 10 Hz for 2 seconds. -The proposed benefits of sweep are a modulated rather than fixed beat frequency, thus avoiding accommodation, and the ability to use both high- and low-frequency stimulation within the same treatment. --------------------------------------------------------------------------------------------------------------------- Premodulated Currents -Premodulated IFC is created by the interference of two alternating currents within the stimulator device, not by interference within the tissues, as with quadripolar IFC. -Thus, only a single current is applied to the patient. Premodulated IFC is delivered using two electrodes instead of four, and is thus sometimes called bipolar IFC. -Russian stimulation is one of the most well-known premodulated currents. --------------------------------------------------------------------------------------------------------------------- Advantages of IFC (1) alternating sinusoidal currents with frequencies exceeding 1 KHz are hypothesized to more easily penetrate the skin due to reduced skin impedance. (2) the amplitudes of the two currents summate in the deeper tissues, thereby passing the more superficial sensory afferent nerves. (3) a beat frequency of the interference current can be selected that is similar to other waveforms used for muscle stimulation and pain modulation. --------------------------------------------------------------------------------------------------------------------- The current flowing between each pair of electrodes is insufficient to stimulate nerve and muscle directly until amplitude is modulated by interference. Interferential therapy thus reduces the stimulation of cutaneous sensory nerves near the electrodes whilst promoting the effect upon deep tissues. Physiological and Therapeutic Effects of IFC 1-Pain relief 2-Motor stimulation 3- Reduction of edema 4- Increase blood flow 5- Stimulation of soft tissue healing and repair --------------------------------------------------------------------------------------------------------------------- 1-Pain relief The interferential current is used in management of acute and chronic pain of different origins, especially post traumatic pain and sympathetically-maintained pain as in shoulder hand syndrome and Raynaud‘s disease (spasm of the digital arteries producing pallor or cyanosis of fingers or toes). Mechanisms of pain control by interferential therapy: - Stimulation with the higher frequencies of about 100 Hz at the sensory level intensities stimulates pain gate mechanisms, thereby mask the pain symptoms - Stimulation with lower frequencies from 2 to 10 Hz at motor level intensities can be used to activate the opoid mechanism, providing a degree of relief. --------------------------------------------------------------------------------------------------------------------- 2-Motor stimulation -Stimulation of the motor nerves to induce contraction of muscle can be achieved with a wide range of frequencies (10 – 50 Hz). Clearly, stimulation at low frequency (1 – 10 Hz) will result in a series of twitches, whilst stimulation at 50 Hz will result in a tetanic contraction. The choice of treatment parameters will depend on the desired effect. --------------------------------------------------------------------------------------------------------------------- 3- Reduction of edema Chronic post-traumatic edema can be reduced by the use of interferential stimulation. This effect may be attributed to milking of the venous and lymphatic return through electrically-evoked contraction. The beat frequency is of approximately 15 Hz or a sweep of 10-25 Hz is often used. --------------------------------------------------------------------------------------------------------------------- - 4- Stimulation of soft tissue healing and repair The interferential current accelerates ossification, so may be used to enhance fracture healing. Furthermore, it may be used also to accelerate wound healing by improving the cellular function and increasing cell proliferation. --------------------------------------------------------------------------------------------------------------------- Indications of Interferential Current 1-Orthopedic conditions -Joint sprains , Fracture complications like delayed union, non-union & retarded callous formation , Osteoarthritis -spondylosis -Frozen shoulder -Chondromalacia 2- Gynecological Problems -Stress incontinence -Urinary frequency -Pelvic floor dysfunction 3-Pain (All types of musculoskeletal pains) -Low back pain -Brachial neuralgia -Sciatica -Phantom limb pain - Myalgia 4-Muscle re-education and muscle strengthening 5- Vasoconstrictive disease (Raynaud‘s Disease) -A disorder where the exposure to cold causes sudden contraction of small arteries supplying the fingers and toes. -Venous insufficiency: Inability of veins to pump the blood towards the heart. 6-Facial nerve neuritis 7- Myositis, Bursitis, and tendinitis. --------------------------------------------------------------------------------------------------------------------- Contraindications 1) Malignant tumours 2) Deep Vein Thrombosis 3) Infective conditions 4) Artificial pacemakers on the heart 5) Pregnant Uterus 6) Condition of haemorrhage 7)Advanced cardiac disease --------------------------------------------------------------------------------------------------------------------- Clinical applications Electrodes placement a) Quadripolar technique: The four electrodes are positioned around the target area so that each channel runs perpendicular to the other and the current crosses at a midpoint. The interference effect branches off at 45° from the center of the treated area, in the shape of a four-leaf clover. Tissues within this area receive the maximal treatment effect. The electrodes are positioned in a coplanar arrangement to treat a flat surface. b) Bipolar technique: When the IF current is applied using a bipolar technique, the mixing of the two channels occurs within the generator rather than in the tissue. This technique does not penetrate the tissues as deeply as quadripolar application, therefore it tends to be of more sensory sensation than with four pole technique, although still less than with low frequency stimulation. In some circumstances, a bipolar technique is preferable if a longitudinal zone requires stimulation rather than an isolated tissue area. When muscle contraction is the goal of the treatment, bipolar electrode placement is used. ---------------------------------------------------------------------------------------------------------------------------------------------------- The pattern of the interferential area Static Interference: The interference effects branch off at 45-degree angles from the center of the treatment, in the shape of a four-leaf clover. Tissues within this area receive the maximal treatment effect, When the electrodes are properly positioned, the stimulation should be felt only between the electrodes, not under the electrodes. Dynamic Interference To increase the area of the interference and stimulate greater tissue area, modulation to the interfered currents can be used. Vector scan, offered on some devices, is the modulation of the amplitude of one or both of the input currents, resulting in a rhythmic change in position of the interference pattern. This is depicted as an oscillating clover- leaf shape, much like the motion of the agitator of a washing machine rotating back and forth. Vector scan is thought to increase the effective treatment area of the stimulation. - It is obtained By slightly unbalancing the currents by varying the current intensity in suitable manner, the interference pattern “rotates” or “scans” 45 degrees back and forth between the electrodes, resulting in treatment of a larger area Treatment Parameters Intensity: -The intensity of the current is dependent on the desired physiological effect and the tissue to be stimulated. -In general, the current could be administered at sensory or motor levels. Frequency: The excitable tissues can be stimulated by low frequency alternating currents. Although to some extent all tissues in this category will be affected by a broad range of stimulations, it is thought that different tissues will have an optimal stimulation band. Motor Nerve 10-50 Hz Sensory Nerve 90-100 Hz --------------------------------------------------------------------------------------------------------------------- Sweep frequency (overcome accommodation ) Nerves are known to accommodate to a constant signal, so a sweep (gradually changing) frequency is often used to overcome this problem. The sweep (range) should be appropriate to the desired physiological effects. The mode of delivery of the selected sweep varies with machines. The most common application is the 6-second rise and fall between the pre-set frequencies. For example, if a 10-25 Hz range has been selected, the machine will deliver a changing frequency, starting at 10 Hz, rising to 25 Hz over a 6second period. Once this upper limit has been achieved, the frequency will once again falls, over a 6-second period to its starting point at 10 Hz. This pattern is repeated throughout the treatment session --------------------------------------------------------------------------------------------------------------------- Treatment duration -Interferential stimulation may be applied once or twice daily in treatment bouts normally ranging from 10 to 20 minutes and may reach to 30 minutes. -Premodulated neuromuscular stimulation bouts are normally applied three times a week in 30-minute bouts. ------------------------------------------------------------------------------------------------------------------------------------------------------ Precautions - Avoid using small electrodes with interferential and premodulated currents. - The high current density combined with the high power (amplitude) of the current may increase the risk of electrical burns of the skin. -This risk may be increased if cold packs are applied concurrently.