Presentation on theme: "LFC: Alternating Currents"— Presentation transcript:
1 LFC: Alternating Currents Minerva Zaniebeth A. Gomez, PTRPDepartment of Physical TherapyCollege of Allied Medical ProfessionsUniversity of the Philippines-ManilaAll rights reserved. Copyright by MZAG, 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.
2 Learning Objectives: Describe Alternating Currents (AC) according to: Physical propertiesClassificationUneven (Faradic currents)Even (Sinusoidal currents)
3 Identify the physiological effects and therapeutic effects of: a. Uneven ACb. Even AC
4 Differentiate the precautions/ contraindications of: a. Uneven ACb. Even AC
5 Select appropriate treatment parameters for indicated cases/ conditions. a. Uneven ACb. Even AC
6 Describe Functional Electrical Stimulation and its therapeutic uses. Select appropriate treatment parameters when using FES for different cases/ conditions.
8 ALTERNATING CURRENT FARADIC Uneven AC SINUSOIDAL Even AC Freq:50 Hz PD: 1 msFreq: 50 HzPD: 10 msCont.InterruptedCont.Interrupted
9 Alternating CurrentPeriodic changes of the direction of electron flow in a rhythmic manner NO NET ion transferFrequency used medically is 50 HzWhen 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.
10 Alternating CurrentNot possible to cause burns, unless in high intensitiesSurged or unsurgedWhen 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.
11 Uneven AC/ Faradic Two phases PD: 1 ms No polarity needed Surged Mild prickling sensationFaradism- 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.
12 Uneven AC/ Faradic NO chemical effects Similar to physiological effects of faradic type currentsIndication and contraindication is the same with faradic-type currents/ SIDCIndication: Pain, swelling , facilitate muscle contraction inhibited by painContraindication: BOILDS + acute inflammation, thrombus formation, psych pt, metals
13 Even AC/ Sinusoidal Sine curve PD: 10 ms Surged or unsurged No polarity neededSurged: to stimulate a muscle. Apply over the nerve supplying the muscleUnsurged: to stimulate a nerve.
14 Indications and Contraindications Indication: Swelling and pain EXCEPT referred & psychosomatic typeContraindication: Skin lesion, Infection, Impaired sensationPain and swelling: except in cases of referred pain and psychosomatic pain.
15 Physiological Effects Sensory nerves: Marked prickling sensation longer durationMotor nerves: Tetanizes, with a sequence of contraction followed by relaxationNO chemical effects
16 Physiological Effects Swelling: Absorption of exudateCirculation: Superficial vasodilation via axon reflex (capillary vasodilation) hyperaemiaVasodilation occurs because of sensory nerve stimulation. Capillary vasodilation occurs if stimulation is prolonged
17 Therapeutic Effects of Even and Uneven AC Facilitate muscle contractionRe-educate muscle actionTrain new muscle actionExercise for paralyzed musclesHypertrophyIncrease strengthImprove circulationPrevent and loosen adhesionsGive as a group activityFacilitate muscle contractionRe-educate muscle actionTrain new muscle actionExercise for paralyzed musclesHypertrophyIncrease strengthImprove circulationPrevent and loosen adhesionsTrain 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.
23 FES for Scoliosis Management Selection Criteria:Curves measuring deg. (Cobb)At least 1 year of spinal growth remainingAn idiopathic and progressive nature of the curveCooperative and psychologically stableCompliant and tolerant to stimulationUsually applied over the stretched muscles on the convex side of the curve for 7-8 hours during sleep.
24 Evidence in PracticeCan FES help improve UE motor recovery of a patient at acute-subacute phase post-stroke?Minerva Zaniebeth A. Gomez, PTRP, PT 158 faculty AY Ma. Liezel Bumanglag, Justine Charlotte Garcia, Marinelle Rabang, Michiko Alla UyPomeroy 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.: CD DOI: / CD pub2.
26 Evidence in PracticeThere is significant change in upper extremity function with the use of electrical stimulation compared to no treatment.Low internal validity (single studies) low powerStatistical pooling not possible because of the heterogeneous characteristics of studies included.
27 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.
28 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