Electro analgesia is the method of electrical nerve stimulation using low pulsed currents to relieve various forms of pains such as low back pain, myofacial pain, arthritic pain, visceral pain, post surgical pain etc. Various methods have been developed to treat pain through the electroanalgesia. The technique behind the electroanalgesia is the Bio- Electric Stimulation Therapy (BEST) in which a small amount of current is passed through the affected body parts so that the current will mimics the electrical signals from the brain. This stimulates the lethargic or non conducting nerve fibers.
Bio-Electric Stimulation Therapy – BEST
It is also known as Micro Current Electrotherapy or MET. It is a specific electro therapy that gives small current into the body. The current is less than one milli ampere. BEST mimics the electrical stimulations of cells by the nerves. This increases the physiology of the cells. BEST has a positive effect on fatigue and chronic pain. BEST boosts energy levels of the cells and restores the homeostasis of the cells by increasing the production of ATP, Transmembrane transport, stimulation of fibroblasts etc.
Electrical Muscle Stimulation – EMS
It is the excitation of muscle contraction using electric pulses. The impulses are delivered through electrodes on the skin close to the muscles that is to be stimulated. The electric impulses from EMS simulate the Action potentials of nerves from the central nervous system causing muscle contraction. Because of the characteristic features of the skeletal muscles, different muscle fibers can be activated by different types of EMS. It is mainly used for rehabilitation purposes. For example, prevention of muscular atrophy after a muscle injury or bone injury. EMS can also cause marginal calorie burning. EMS is used by some athletes in sports training.
EMS is classified into two types namely Over- the Counter Devices (OTC) andPrescription devices. OTC is aimed for muscle toning and is freely available in the market. The Prescription devices require a medical prescription and can be used only under medical supervision. The Prescription devices are mainly used for reducing muscle spasm, prevention of muscular atrophy, post surgical stimulation of muscles, to increase blood circulation into the muscles etc.
Unregulated marketing and use of EMS needs attention. Since these devices apply electric pulses into the body, all precautionary measures should be adopted to prevent shocks, burns etc. It may also affects the implanted pace makers. So it is advisable to use EMS manufactured by reputed firms and its use must be as per the directions or with the supervision of a medical practitioner.
EMS Unit
Micro current Electrical Neuromuscular Stimulator – MENS
It is the device used to give weak electrical signals into the body. MENS gives very small current less than 1 milli ampere to nerves using micro electrodes placed on the skin. It is used in treatment of wound healing, tendon repair, ligament recover etc.
Percutaneous Electrical Nerve Stimulator – PENS
It is a combined form of Electro acupuncture and Transcutaneous Nerve Stimulator (TENS). PENS uses acupuncture like needles as electrodes. These electrodes are placed at dermatomal levels. PENS bypass the local skin resistance and give the desired current to the nerve endings.
Transcutaneous Electrical Nerve Stimulation - TENS.
TENS is used in Palliative care and pain medicine to relieve pain in the affected parts of the body. It is recommended in cases of neuropathic pain caused by nerve damage. The effect of TENS depends on the individual’s physiology and response to electrical stimuli and the pain threshold. The TENS unit consists of one or more electrodes, a pulse generator and power source battery. The circuit inside the TENS is programmable to generate pulses of electrical stimuli with variable current strength, pulse rate and pulse widths. The waveform from the TENS is biphasic so that electrolytic effects on the skin can be eliminated. The important parameters used in TENS for the patient’s comfort are
1. Amplitude of Signal – A comfortable strength of current of low intensity, just above the threshold level is applied to the skin.
2. Pulse rate – Frequency of 80 – 100 impulses per second are used.
3. Pulse width – Duration of electrical pulses between 10 – 1000 micro seconds.
Patients are instructed to select the correct frequency and intensity of pulses at which they feel free from pains. This can be found out by trial and error. Usually the electrodes are placed on the skin of the painful area. TENS have three settings to use in different therapeutic methods. The Conventional TENS uses a frequency of 40 – 150 Hz with low intensity and the current between 10 – 30 mA. Pulse duration is set at the maximum of 50 micro seconds. In Acupuncture mode, the frequency is set at 1-10 Hz at high intensity close to the tolerance limit. In Pulsed Mode, low intensity stimuli are applied as high frequency bursts around 1 – 2 Hz.
How these Electro stimulants work?
Bioelectric Stimulation Therapy (BEST) is the technique in which very small current is passed through the Skin of an affected region to relieve pain. This pulsed current will mimic the natural action potentials of the nerves so that the nerve conduction will be activated.
Physiological aspects
BEST is based on the electrical conductivity of the Skin and the electrical activities of the nerves. The current output from the device depends on the combined impedance of the electrodes, skin and muscle tissue. When repetitive discharges are applied to the same area of the skin. The impedance of the skin reduces which results in the flow of greater current through the skin. Studies have shown that these devices reduce pain through the inhibition of the Dorsal Horn of the Spinal cord thus limiting its central transmission. The electrical stimuli applied to the skin activate the low threshold Myelinated nerve fibers. The Afferent input from these fibers inhibits the flow of impulses in non Myelinated “C fibers”. This blocks the transmission of impulses to the “target cells” present in the dorsal horn. High frequency TENS activates the “Delta Opioid” receptors present in the Spinal cord and medulla while low frequency TENS activates the “Mu-Opioid” receptors in the spinal cord and medulla. High frequency TENS causes the inhibition of “Excitatory Neuro transmitters” like Glutamate and increases the production of “Inhibitory Neurotransmitters” like GABA ( Gamma Amino Butyric Acid ) in the spinal cord. At the same time, the “Muscarinic receptors” present in the Central Nervous system is activated. This causes a temporary blocking of the “Pain Gate” leading to Analgesia.
The low frequency TENS causes the release of the Neurotransmitters Serotonin and activates Serotonin receptors in the spinal cord. The production of GABA is also activated.
Safety considerations
Since pulsed electrical signals are used in Electro stimulants, adequate safety measures should be adopted while using the TENS electrodes.
1. Electrodes should not be used on or near the eyes, mouth, front part of the neck, on the area of numb skin, on wounds, on the facial nerves etc.
2. These devices should not be used in pregnant woman or persons having artificial pace maker.
3. TENS should be used with caution if there is a history of Epilepsy.
D.Mohan kumar
