Strength-Duration Curves (S-D) PDF

STRENGTH-DURATION (S-D) CURVES PHYSICAL AGENTS III Degree of Physiotherapy San Pablo-CEU University 2022-2023 OUTLINE • INTRODUCTION AND CONCEPT • ELECTRODE PLACEMENT. • STEPS TO FOLLOW AND APPLICATIONS. • PARAMETERS • EXAMPLES 2 CONCEPT • S-D curves Illustrate the relationship between curren...

STRENGTH-DURATION (S-D) CURVES PHYSICAL AGENTS III Degree of Physiotherapy San Pablo-CEU University 2022-2023 OUTLINE • INTRODUCTION AND CONCEPT • ELECTRODE PLACEMENT. • STEPS TO FOLLOW AND APPLICATIONS. • PARAMETERS • EXAMPLES 2 CONCEPT • S-D curves Illustrate the relationship between current amplitude and pulse duration required to produce a threshold stimulus to create an action potential in different types of nerve fibers and directly in denervated skeletal muscle fibers. from rectangular to triangular • AIM: Maintain the functional state of the neuromuscular system or strengthen the muscles. 3 S-D CURVES • An external electrical stimulus needs more intensity to produce the same stimulus as pulse duration decreases. normal m. only in rectangular shape: short pulse duration so need more intensity long pulse duration -> less intensity needed in m. without nerve injury bc progressive increase in intensity -> get accomodated 4 times more intensity than injured one for ex 7mA if injured m. muscle is denervated and need more time to contract 4 ELECTRODE PLACEMENT • MONOPOLAR best ones – ANODE: Neutral, over the plexus. big size – CATHODE: Active over MMP or NMP. small over muscle motor point or nerve motor point • VARIATION: • BIPOLAR third option – ANODE: Proximal. – CATHODE: Distal. over m. not tendon 2 – ANODE: Neutral, over NMP. – CATHODE: Active over MMP. 5 STEPS TO FOLLOW first step (blue one) with rectangular pulses: biggest pulse duration (1s) to smallest i • BEGIN USING RECTANGULAR PULSES. – PULSE DURATION: 1000 ms. time o – INTERVAL DURATION 3 seconds. 1s in red: second step from 0 to 1s in triangular pulses – Decrease pulse duration from 1000 ms to 0 ms. – Join the points using lines. • DO THE SAME WITH TRIANGULAR PULSES. try to be objective without looking to machine looking for a contraction • DO NOT LOOK AT THE INTENSITY TILL THERE IS A CONTRACTION!!!. we are looking for minimal contraction 6 STEPS TO FOLLOW we decrease time and observe where the contraction is happening, PD shorter so I is higher (red one, rectangular, from right to left) triangular shape, from left to right, U letter, sometimes the sensation of burning can be very strong for the patient so sometimes the graph stops at 500 on healthy m. to compare as well mA (I) time 7 APLICATIONS AND INFORMATION the more up and more to the right pb with nerve and muscle if only going up -> muscle pb only • TYPE AND DEGREE OF DAMAGE. if m. injury or nerve affected if pb -> graph goes up if we use rectangular pulse in denervation we will need higher intensity and we will recruit not only injured fibers but also healthy fibers we lose the accomodation that we have with triangular pulse • SHAPE AND PULSE DURATION. • INTERVAL TIME. • BURST OR ISOLATED PULSES APPLICATION 4-6" isolated is one pulse with 4-6s break then anotehr one burst if denervation -> isolated if injury worst -> ttmt with triangular or isolated pulse 8 GRAPH WITH RECTANGULAR PULSES mA 1. 2. 3. 4. CHRONAXIC PART RHEOBASE always in mA MUSCLE UTILIZATION TIME (MUT) FARADIC THRESHOLD. CHRONAXIE. intensity is always the same until one point= m. utilization time 4 AREA WITH RESPONSE RHEOBASIC PART 3 1 2 AREA WITH NO RESPONSE 1mA ms 9 RHEOBASE • Minimum intensity needed to produce a minimum contraction with a rectangular pulse of 1000 ms. always in the vertical line of 1000ms • The normal values will depend on the size of the electrodes, skin humidity, depth of the fat tissue, etc. • Normal values: 1-10 mA. if rheobase higher -> pb but we don't know if it's affecting nerve or m. MUT: end of rheobasic part MUT for nerve MUT for a muscle (right part of graph) m. fibers respond with bigger PD that reacts with shorter PD if there are those steps: means there is a denervation or the nerve is reinnervated (nerve is rsponding) only one MUT if healthy muscle 10 MUSCLE UTILIZATION TIME (MUT) • In normal conditions there is ONLY one which matches with the first increase in height and the end of the rheobasic part. • But there are 2 MUT (one for the muscle being the first and other for the nerve being the second) when there is a moderate denervation or reinnervation (steps). • Normal values: 1-10 ms. 11 rectangular FARADIC THRESHOLD • Minimum intensity needed to produce a minimum contraction with a rectangular pulse of 1 ms. • If the curve crosses the vertical line of 1 ms: BURST OF RECTANGULAR PULSES are needed for the treatment; if not ISOLATED RECTANGULAR PULSES. very important denervation in this case the graph does not cross 1ms vertical line so we use isolated pulses for ttmt when graph is crossing the 1ms vertical line it means we can use for ttmt burst of rectangular pulses 1ms 12 CHRONAXIE • The chronaxie is going to be the best pulse duration to get the minimum contraction with an intensity double than the real rheobase Chronaxie is the best pulse duration except for denervation when chronaxie will demand higher intensities (muscle utilization time). best pulse duration when we are using rectangular, biphasic symmetric • It is the ideal pulse duration for muscle strengthening with rectangular pulses (alternant or monophasic) representing the time to get the minimum energy consumption with the higher energetic efficiency. • Normal values: 0,1-0,7 ms (100-700 μs). 7x2= 14 demands high intensity: very uncomfortable for patients if too much for patient -> we use MUT 7 rhebose x2 and then horizontal line crossing the graph = chronaxie the more denervation the more in the right the higher the chronaxie value, the bigger the denervation chr mut 13 CHRONAXIE (DENERVATION) • WEEKLY DENERVATED: – 1-3 ms. • MODERATELY DENERVATED: – 3-6 ms. higher value for chronaxie higher the denervation • SERIOUSLY DENERVATED: – 6-30 ms. • COMPLETELY DENERVATED: – > 30 ms. 14 FISHGOLD TEST/BAWEN’S INDEX • Intensity 1ms/intensity 100 ms intensity at 1ms divided by the intensity found at 100ms not rheobase • If the result is under 2 the innervation is normal. 15 RHEOBASIC AND CHRONAXIC PART • Rheobasic part: From rheobase to MUT • High and short: hypoexcitability • Low and long: hyperexcitability. horizontal part pf the graph very high intensity to achieve contraction in case of injury of first motor neuron contraindication to use these currents • Chronaxic part: from MUT till the end of the curve. end of cruve and not vertical line of 0 bc sometimes we don't reach it hypoexcitabiity hyper excitability 16 GRAPHIC WITH TRIANGULAR PULSES mA FARADIZATION PART OR FARADIC ACCOMODATION 1. GALVANO TETANUS THRESHOLD 1 2. DEFLEXION ANGLE 1000ms 3. FARADIC THRESHOLD. AREA WITH RESPONSE 3 angulation tense to 45 or to 0: decision to use triangular or rectangular pulses faradic threshold 1ms 2 ACCOMODATION PART OR ANODIC ACCOMODATION mS17 GALVANO TETANUS THRESHOLD (GTT) • Minimum intensity needed to produce a minimum contraction with a triangular pulse of 1000 ms. no normal values, we only use this value to calcuate the next one 18 ACCOMODATION INDEX AI= GTT (at 1000ms) / rheobase (at 1000ms) should always have a value from 3 to 6 • GALVANO TETANUS THRESHOLD (GTT)/RHEOBASE. • NORMAL: – 3-6----------2’5-3’5*. • PARTIAL DENERVATION: – 2’7-1’5-----1’5-1’1*. the lower the nbr the worst the denervation • TOTAL DENERVATION: – 1’4-1--------1*. * GTT calculated with Intensity of 500 ms. sometimes not able to finish the graph bc too uncomfortable for patients so we calculate AI= GTT (at 500ms)/ rheobase (at 1000ms) 19 DEFLEXION ANGLE • It is the point where the graph ends its decrease to start increasing again. isolated • It is the ideal pulse duration using triangular pulses and the ideal interval pulse to use with rectangular pulses. ideal PD in case we use isolated triangular pulses or interval duration in case we use rectangular pulses (not the off, btwn two rectangular pulses) ID on off on 20 FARADIC THRESHOLD • Minimum intensity needed to produce a minimum contraction with a triangular pulse of 1 ms. 21 FARADIC PART vs ACCOMODATION PART rectangular or triangular pulses • Accomodation part/anodic accomodation from the GTT till the deflexion angle. • Faradic part/faradic accomodation: deflexion angle till the end of the curve. from the if 45 degrees -> normal accomodation if tends to 0 degree -> no normal accomodation if tends to 0 (no accomodation) = we should use triangular pulses if tends to 45= we cannot use triangular bc accomodation so we will use rectangular 22 ACCOMODATION PART/ANODIC ACCOMODATION • The angle formed by the curve and the horizontal line. • If it tends to the horizontal line, there is an accomodation loss; if it tends to 45º there is normal accomodation. 23 THERAPEUTIC UTILIZATION TRIANGLE blue= healthy bc angle tends to 45 degrees red= unhealthy m. bc angle tends to 0 only healhty m. contracts we adapt PD until only contraction of unhealthy m. both m. contract pd and intensity that are oly goung to contract ²affected fibers 24 ACCOMODATION: DENERVATION • ACCOMODATION DEPENDS ON GOOD METABOLISM: – State Na+ channels and Na+ /K+ pump – Ionic intra-extracelular proportion. • DENERVATION: – More intensity and pulse width. – Accomodation capacity is lost. – Slow response. – Prolongued repolarization during seconds: ISOLATED PULSES. – Accomodation with triangular pulses similar to rectangular pulses. 25 CUBITAL NERVE INVOLVEMENT diagnosis: denervation burst of triangular pulses (not big enough denervation -> touch 1ms line) on: 2-4 off: 4-8 PD: 20ms ID: 30ms tends to 0°: accomodation loss triangular pulses for ttmt normal value (1-10mA) GTT IA NV: 3 to 6 MUT not normal (1-10ms -> maybe denervation ?) deflexion angle rectangular faradic threshold 2.32 (normal value is under 2) rheobase x 2 -> then look at the pd => weekly denervation 26 NEUROPATHY CAUSED BY COLD EXPOSITION burst of rectangular pulse in this case, chronaxie is always the pd ID: deflexion on: 2-4" off: 4-8" ice for 24h for ankle sprain -> neropraxia AI= close to normal 2.1 bc not on ranges bawen index: 6.7/1.5 4,46 -> serious denervation ok gtt at 500 not 1000 not ok 27