Understanding Sympathetic Skin Response (SSR) and RR Interval: A Comprehensive Analysispptx

This presentation provides an in-depth exploration of the physiological principles, clinical significance, and applications of Sympathetic Skin Response (SSR) and RR Interval

1. SSR & RR INTERVAL Created by:) Jose BSc NST

2. SSR or Sympathetic skin response is the potential generated by sweat glands in response to a variety of stimulations. It measures the change in the electrical potential of the skin. It is a pseudomotor function test that occurs as a result of reduction in electrical resistance of the skin in response to stimulations . SSR is useful in studying the integrity of peripheral sympathetic function by evaluating the changes in resistance of skin to electric conduction.

3. Procedure Active electrodes – are placed on the palmar or plantar (sole) aspects of hand and foot respectively. Reference – over the dorsum of respective body after cleaning the skin. Disc electrodes are used for recording. Any mode of stimulation is used but electrical stimulation (10-12mV) of digital nerve is commonly employed. Other modes of stimulations include startling sound or deep inspiratory gasp.

4. Limb temperature is maintained above 30°C (32-34) Absence of SSR response is confirmed only after ensuring adequate stimulations and excluding habituation which can be acheived by giving more intense stimilation . ( Noxious stimuli) Machine settings-: LFF – 0.1 or 0.5 Hz. HFF – 500-1000 Hz. Gain – 0.5- 3 mV.

5. SSR is monophasic, diphasic or triphasic and it can be varied according to stimulations given. SSR is a sinusoidal waveform. Types of Waveform- P –type : which is having a maximum postive defelction . N –type: which is having a maximum negative deflection. Maximal peak to peak amplitudes and mean latencies are measured. Variability of the latter factors can be minimized by reducing stimulus frequency, increasing stimulus intensity and changing stimulus site or node.

6. P Type N type

7. SSR potentials are symmetric in homologous body regions and these have higher amplitudes and shorter latency in hands compared to feet.

8. Factors affecting SSR Age – SSR is age dependent and is present in both hands and feet till age of 60 years. Limb temperature – Cooling results in prolongation of latency and reduction in amplitudes. Habituation – diminished innate response to a frequently repeated stimulus. Other parameters include composition of surface electrode, amplifiers, time constant, stimulus frequency

9. Normal values Amplitude-- For Hands: more than 1mV. For foot: more than 0.2 mV. Latency -- Mean palmar latency: 1.4± 0.1 sec Plantar: 1.9± 0.1 sec

10. Ssr abnormality SSR responses absent are observed in; a) Dysautonomia -: condition in which nerves which regulate non voluntary body functions will get disfunctioned , affecting HR, BP and sweating. b)DM patients. c) CVA & SCI d)Demyelinating neuropathies Latencies, Amplitudes may be prolonged or decreased in early and entrapment neuropathy.

11. RR interval RR Interval is a parasympathetic function testing of Heart rate. It is the time elapsed between two successive R waves of QRS complex in an ECG wave. It is the reciprocal of Heart rate and is a function of intrinsic properties of SA node. RR interval is used for 2 purposes; •to calculate HR •if the HR is normal or not. Normal RR = 12-16 bpm.

12. HR can be calculated from ECG wave as follows; HR = 1500/ RR interval (in mms). HR = 60/ RR interval (in secs). High RR indicates high respiratory rate. Mean RR Interval:- Following values are calculated; > Standard Deviation of mean RR interval. > Mean square successive difference.

13. 30:15 RR ratio— ECG allows determination of 30:15 RR ratio. That is the ratio of longest RR interval (slow HR) occuring about 30 beats divided by shortest RR interval (fastest HR) which occur about 15 bpm after standing. The 30:15 ratio is normal when it is >1.04 and is abnormal when it is <1.0 Age related RR values; 10-30  1.17 30-50  1.09 50-65  1.03

14. Deep Breathing- Deep breathing at a rate of 5-6 cycles per minute is done allowing 5 secs each for inspiration and expiration. Here max and min HR is calculated with which RR interval is evaluated and thereby estimate the mean deviation. E/I ratio = sum of 6 longest RR / sum of 6 shortest RR

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