LFC: Alternating Currents Minerva Zaniebeth A. Gomez, PTRP Department of Physical Therapy College of Allied Medical Professions University of the Philippines-Manila All rights reserved. Copyright by MZAG, 2009. Use exclusively for PT 158: Physical Agents iII. Approval and consent from Minerva Zaniebeth A. Gomez and University of the Philippines-Manila required before use for other purposes. (mzagomez@upm.edu.ph)

Learning Objectives: Describe Alternating Currents (AC) according to: Physical properties Classification Uneven (Faradic currents) Even (Sinusoidal currents)

Identify the physiological effects and therapeutic effects of: a. Uneven AC b. Even AC

Differentiate the precautions/ contraindications of: a. Uneven AC b. Even AC

Select appropriate treatment parameters for indicated cases/ conditions. a. Uneven AC b. Even AC

Describe Functional Electrical Stimulation and its therapeutic uses. Select appropriate treatment parameters when using FES for different cases/ conditions.

Appreciate evidence on the use of FES

ALTERNATING CURRENT FARADIC Uneven AC SINUSOIDAL Even AC Freq:50 Hz PD: 1 ms Freq: 50 Hz PD: 10 ms Cont. Interrupted Cont. Interrupted

Alternating Current Periodic changes of the direction of electron flow in a rhythmic manner  NO NET ion transfer Frequency used medically is 50 Hz When an AC flows in a conductor, the total number of electrons that move in one direction = the total no. of electrons that move in the reverse direction. Hence, if ions in a solution is energised by the AC, they will just move to and fro between the electrodes and no net ion transfer will occur. Will not cause chemical burns compared to DC. Ions that move one way during one phase of current and reverse in direction during the other phase, so chemicals formed during one phase is neutralized by the next phase.

Alternating Current Not possible to cause burns, unless in high intensities Surged or unsurged When an AC flows in a conductor, the total number of electrons that move in one direction = the total no. of electrons that move in the reverse direction. Hence, if ions in a solution is energised by the AC, they will just move to and fro between the electrodes and no net ion transfer will occur. Will not cause chemical burns compared to DC. Ions that move one way during one phase of current and reverse in direction during the other phase, so chemicals formed during one phase is neutralized by the next phase.

Uneven AC/ Faradic Two phases PD: 1 ms No polarity needed Surged Mild prickling sensation Faradism- production of uneven alternating current through an induction coil. Two phases: because it uses a frequency of 50 Hz followed by a damped oscillation of 1000 Hz (intensity is too low to cause excitation) Surging: to control peak intensity to produce a near normal tetanic-like contraction and relaxation of muscle.

Uneven AC/ Faradic NO chemical effects Similar to physiological effects of faradic type currents Indication and contraindication is the same with faradic-type currents/ SIDC Indication: Pain, swelling , facilitate muscle contraction inhibited by pain Contraindication: BOILDS + acute inflammation, thrombus formation, psych pt, metals

Even AC/ Sinusoidal Sine curve PD: 10 ms Surged or unsurged No polarity needed Surged: to stimulate a muscle. Apply over the nerve supplying the muscle Unsurged: to stimulate a nerve.

Indications and Contraindications Indication: Swelling and pain EXCEPT referred & psychosomatic type Contraindication: Skin lesion, Infection, Impaired sensation Pain and swelling: except in cases of referred pain and psychosomatic pain.

Physiological Effects Sensory nerves: Marked prickling sensation  longer duration Motor nerves: Tetanizes, with a sequence of contraction followed by relaxation NO chemical effects

Physiological Effects Swelling: Absorption of exudate Circulation: Superficial vasodilation via axon reflex (capillary vasodilation)  hyperaemia Vasodilation occurs because of sensory nerve stimulation. Capillary vasodilation occurs if stimulation is prolonged

Therapeutic Effects of Even and Uneven AC Facilitate muscle contraction Re-educate muscle action Train new muscle action Exercise for paralyzed muscles Hypertrophy Increase strength Improve circulation Prevent and loosen adhesions Give as a group activity Facilitate muscle contraction Re-educate muscle action Train new muscle action Exercise for paralyzed muscles Hypertrophy Increase strength Improve circulation Prevent and loosen adhesions Train new muscle action: after tendon transplant/ reconstruction, the muscle may be required to perform a different action from that of before. Exercise for paralyzed muscle: in cases of neuropraxia only since the nerve is still intact in this case. A faradic response indicates that there is nerve recovery already.

TECHNIQUES OF APPLICATION

Functional Electrical Stimulation Functional NMES Used for: -disuse atrophy - impaired ROM - ms spasm - ms reeducation - spasticity - supplement to orthotic devices

FES for Shoulder Subluxation Waveform: Asymmetrical biphasic square Modulation: Interrupted Electrodes are placed on supraspinatus or posterior deltoid

FES for DF Assist in Gait Training Waveform: Assymetrical biphasic square PD: 20-250 µsec Modulation: interrupted by foot switch

FES for Scoliosis Management Selection Criteria: Curves measuring 20-45 deg. (Cobb) At least 1 year of spinal growth remaining An idiopathic and progressive nature of the curve Cooperative and psychologically stable Compliant and tolerant to stimulation Usually applied over the stretched muscles on the convex side of the curve for 7-8 hours during sleep.

Evidence in Practice Can FES help improve UE motor recovery of a patient at acute-subacute phase post-stroke? Minerva Zaniebeth A. Gomez, PTRP, PT 158 faculty AY 2008-2009(mzagomez@upm.edu.ph), Ma. Liezel Bumanglag, Justine Charlotte Garcia, Marinelle Rabang, Michiko Alla Uy Pomeroy V. M., King, L., Pollock, A., Baily-Hallam, A., and Langhorne, P. (2006). Electrostimulation for promoting recovery of movement or functional ability after stroke. Cochrane Database of Systematic Reviews 2006, Issue 2. Art. No.: CD003241. DOI:10.1002/14651858.CD003241.pub2.

FES of hand extensors

Evidence in Practice There is significant change in upper extremity function with the use of electrical stimulation compared to no treatment. Low internal validity (single studies)  low power Statistical pooling not possible because of the heterogeneous characteristics of studies included.

Evidence in Practice Wide confidence interval crosses zero point Heterogenous settings of parameters used “FES” loosely used term among PTs. Statistical pooling not possible because of the heterogeneous characteristics of studies included.

References: Gersh, M. R. (1992). Electrotherapy in Rehabilitation. USA: F.A. Davis Company. Hecox, B., Mehreteab, T. A., & Weisberg, J. (1994). Physical Agents: A Comprehensive Text for Physical Therapist. Appleton & Lange. Wadsworth, H., & Chanmugam, A. (1988). Electrophysical Agents in Physiotherapy. Singapore: Science Press.  Revised ACDC lecture of Ms. Jazel Ann Atienza, PTRP