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Autonomic
Function Tests
Prof Vajira Weerasinghe
Professor of Physiology
Available at www.slideshare.net/vajira54
Autonomic Nervous system
Objectives
Describe the physiological basis of the following autonomic
function tests in relation to cardiovascular system...
1. Heart rate variation during
respiration
• The variation of heart rate with respiration is known as
sinus arrhythmia
• I...
Sinus Arrhythmia
Explanation for sinus
arrhythmia
• Due to changes in vagal control of heart
rate during respiration
• Probably due to foll...
Heart rate variation during
respiration
• Heart rate increases during inspiration due to
decreased cardiac vagal activity ...
Deep breathing
Procedure
• Connect the ECG electrodes for recording lead II
• Ask the subject to breath deeply at a rate of six
breaths p...
Procedure
• Record maximum and minimum heart rate with each
respiratory cycle
• Average the 3 differences
– Normal > 15 be...
Procedure
• Determine the expiration to inspiration
ratio (E:I ratio)
E:I ratio
• Mean of the maximum R-R intervals
during deep expiration to the mean of
minimum R-R intervals during deep
insp...
E:I ratio
longest RR interval (expiration)
Ratio = -------------------------------------
shortest RR interval (inspiration...
2. Heart rate variation during
postural change
• Changing posture from supine to standing leads
to an increase in heart ra...
Heart rate variation during
postural change
• On standing the heart rate increases until it
reaches a maximum at about
– 1...
Heart rate response to
standing from supine posture
30:15 ratio
• The ratio of R-R intervals corresponding to the 30th
and 15th
heart beat  30:15 ratio
RR interval at 30th
b...
30:15 ratio
RR interval at 30th
beat
•30:15 ratio = ------------------------------
RR interval at 15th
beat
•Normal > 1.04...
3. Valsalva Manoeuvre
• Assesses integrity of the baroreceptor
reflex
• Measure of parasympathetic and
sympathetic functio...
Valsalva Manoeuvre
• The Valsalva
maneuver is
performed by
attempting to forcibly
exhale while keeping
the mouth and nose
...
Procedure
• Perform the Valsalva manoeuvre (forced
expiration against a closed glottis) by asking the
subject to breathe f...
Valsalva Manoeuvre
• 4 phases
– Phase I
– Phase II
– Phase III
– Phase IV
Four Phases
– Transient increase in BP which lasts for a few seconds
– HR does not change much
– Mechanism: increased intrathoracic pr...
Phase II - Phase of straining
• Early part – drop in BP lasting for about 4 seconds
• Latter part – BP returns to normal
•...
Mechanism
• Early part
– venous return decreases with compression of veins by
increased intrathoracic pressure central ve...
Phase III - Release of straining
• Transient decrease in BP lasting for a
few seconds
• Little change in heart rate
Mechanism
• Mechanical displacement of blood
into pulmonary vascular bed, which
was under increased intrathoracic
pressure...
Phase IV – further release of strain
• BP slowly increases and heart rate proportionally decreases
• BP overshoots
• Occur...
Mechanism
• Due to increase in venous return, stroke
volume and cardiac output
• With this high pressure there is no venous
return since no venous blood can enter
the thorax
• The blood in the lungs an...
Phases
♦ Phase I Decrease in BP
♦ Phase II Decrease in BP, Tachycardia
♦ Phase III Decrease in BP
♦ Phase IV Overshoot of ...
Valsalva Ratio
• Measure of the change of heart rate that takes
place during a brief period of forced expiration
against a...
Valsalva Ratio
Longest RR
Valsalva Ratio = -----------------------------
Shortest RR
≥ 1.4
Values
• more than 1.21  norma...
Valsalva manoeuvre
• Valsalva maneuver evaluates
– 1. sympathetic adrenergic functions using the
blood pressure responses
...
4. Cold pressor test
• Submerge the hand in ice cold water
• This increases
– systolic pressure by about 20 mmHg
– diastol...
Medullary
cardiovascular
control
center
Carotid and aortic
baroreceptors
Change in
blood
pressure
Parasympathetic
neurons
...
Figure 15-21 (1 of 10)
Blood Pressure
Change in
blood
pressure
Integrating center
Stimulus
Efferent pathway
Effector
Senso...
Figure 15-21 (2 of 10)
Blood Pressure
Carotid and aortic
baroreceptors
Change in
blood
pressure
Integrating center
Stimulu...
Figure 15-21 (3 of 10)
Blood Pressure
Medullary
cardiovascular
control
center
Carotid and aortic
baroreceptors
Change in
b...
Figure 15-21 (4 of 10)
Blood Pressure
Medullary
cardiovascular
control
center
Carotid and aortic
baroreceptors
Change in
b...
Figure 15-21 (5 of 10)
Blood Pressure
Medullary
cardiovascular
control
center
Carotid and aortic
baroreceptors
Change in
b...
Figure 15-21 (6 of 10)
Blood Pressure
Medullary
cardiovascular
control
center
Carotid and aortic
baroreceptors
Change in
b...
Figure 15-21 (7 of 10)
Blood Pressure
Medullary
cardiovascular
control
center
Carotid and aortic
baroreceptors
Change in
b...
Figure 15-21 (8 of 10)
Blood Pressure
Medullary
cardiovascular
control
center
Carotid and aortic
baroreceptors
Change in
b...
Figure 15-21 (9 of 10)
Blood Pressure
Medullary
cardiovascular
control
center
Carotid and aortic
baroreceptors
Change in
b...
Figure 15-21 (10 of 10)
Blood Pressure
Medullary
cardiovascular
control
center
Carotid and aortic
baroreceptors
Change in
...
Baroreceptor Reflex
Valsalva manoeuvre in diabetic autonomic
neuropathy
Other ANS tests in CVS
• Head up tilt test (HUT)
– Heart rate and BP response
• BP Response to standing
• BP Response to s...
Autonomic function tests
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Transcript of "Autonomic function tests"

  1. 1. Autonomic Function Tests Prof Vajira Weerasinghe Professor of Physiology Available at www.slideshare.net/vajira54
  2. 2. Autonomic Nervous system
  3. 3. Objectives Describe the physiological basis of the following autonomic function tests in relation to cardiovascular system 1. Heart rate variation during respiration 2. Heart rate variation during postural change 3. Valsalva manoeuvre (maneuver) 4. Cold pressor test
  4. 4. 1. Heart rate variation during respiration • The variation of heart rate with respiration is known as sinus arrhythmia • Inspiration  increases the heart rate • Expiration  decreases the heart rate • This is also called Respiratory Sinus Arrhythmia (RSA) • This is an index of vagal control of heart rate
  5. 5. Sinus Arrhythmia
  6. 6. Explanation for sinus arrhythmia • Due to changes in vagal control of heart rate during respiration • Probably due to following mechanisms – Influence of respiratory centre on the vagal control of heart rate – Influence of pulmonary stretch receptors on the vagal control of heart rate
  7. 7. Heart rate variation during respiration • Heart rate increases during inspiration due to decreased cardiac vagal activity and decreases during expiration due to increased vagal activity • This is detected by recording the heart rate by using the electrocardiograph while the subject is breathing deeply
  8. 8. Deep breathing
  9. 9. Procedure • Connect the ECG electrodes for recording lead II • Ask the subject to breath deeply at a rate of six breaths per minute for 3 cycles (allowing 5 seconds each for inspiration and expiration)
  10. 10. Procedure • Record maximum and minimum heart rate with each respiratory cycle • Average the 3 differences – Normal > 15 beats/min – Borderline = 11-14 beats/min – Abnormal < 10 beats/min
  11. 11. Procedure • Determine the expiration to inspiration ratio (E:I ratio)
  12. 12. E:I ratio • Mean of the maximum R-R intervals during deep expiration to the mean of minimum R-R intervals during deep inspiration
  13. 13. E:I ratio longest RR interval (expiration) Ratio = ------------------------------------- shortest RR interval (inspiration) E:I = 1.2
  14. 14. 2. Heart rate variation during postural change • Changing posture from supine to standing leads to an increase in heart rate immediately, usually by 10-20 beats per minute
  15. 15. Heart rate variation during postural change • On standing the heart rate increases until it reaches a maximum at about – 15th beat (shortest R-R interval after standing) – after which it slows down to a stable state at about – 30th beat (longest R-R interval after standing)
  16. 16. Heart rate response to standing from supine posture
  17. 17. 30:15 ratio • The ratio of R-R intervals corresponding to the 30th and 15th heart beat  30:15 ratio RR interval at 30th beat • 30:15 ratio = ------------------------------ RR interval at 15th beat • This ratio is a measure of parasympathetic response
  18. 18. 30:15 ratio RR interval at 30th beat •30:15 ratio = ------------------------------ RR interval at 15th beat •Normal > 1.04 •Borderline = 1.01-1.04 •Abnormal =<1.00
  19. 19. 3. Valsalva Manoeuvre • Assesses integrity of the baroreceptor reflex • Measure of parasympathetic and sympathetic function • It is “forced expiration against a closed glottis”
  20. 20. Valsalva Manoeuvre • The Valsalva maneuver is performed by attempting to forcibly exhale while keeping the mouth and nose closed • It increases intrathoracic pressure to as much as 80 mmHg
  21. 21. Procedure • Perform the Valsalva manoeuvre (forced expiration against a closed glottis) by asking the subject to breathe forcefully into a mercury manometer and maintain a pressure of 40 mmHg for 15 seconds • Record the ECG throughout and for 30 seconds after the procedure
  22. 22. Valsalva Manoeuvre • 4 phases – Phase I – Phase II – Phase III – Phase IV
  23. 23. Four Phases
  24. 24. – Transient increase in BP which lasts for a few seconds – HR does not change much – Mechanism: increased intrathoracic pressure and mechanical compression of great vessels due to the act of blowing Phase I – Onset of straining
  25. 25. Phase II - Phase of straining • Early part – drop in BP lasting for about 4 seconds • Latter part – BP returns to normal • Heart rate rises steadily
  26. 26. Mechanism • Early part – venous return decreases with compression of veins by increased intrathoracic pressure central venous pressure decreases  BP decreases • Latter part – drop in BP in early part will stimulate baroreceptor reflex  increased sympathetic activity  increased peripheral resistance  increased BP ( returns to normal ) • Heart rate increase steadily throughout this phase due to vagal withdrawal in early part & sympathetic activation in latter part
  27. 27. Phase III - Release of straining • Transient decrease in BP lasting for a few seconds • Little change in heart rate
  28. 28. Mechanism • Mechanical displacement of blood into pulmonary vascular bed, which was under increased intrathoracic pressure  BP decreases
  29. 29. Phase IV – further release of strain • BP slowly increases and heart rate proportionally decreases • BP overshoots • Occurs 15-20 s after release of strain and lasts for about a minute or more
  30. 30. Mechanism • Due to increase in venous return, stroke volume and cardiac output
  31. 31. • With this high pressure there is no venous return since no venous blood can enter the thorax • The blood in the lungs and heart will be expelled at a higher pressure than normal
  32. 32. Phases ♦ Phase I Decrease in BP ♦ Phase II Decrease in BP, Tachycardia ♦ Phase III Decrease in BP ♦ Phase IV Overshoot of BP, Bradycardia
  33. 33. Valsalva Ratio • Measure of the change of heart rate that takes place during a brief period of forced expiration against a closed glottis • Ratio of longest R-R interval during phase IV (within 20 beats of ending maneuver) to the shortest R-R interval during phase II • Average the ratio from 3 attempts
  34. 34. Valsalva Ratio Longest RR Valsalva Ratio = ----------------------------- Shortest RR ≥ 1.4 Values • more than 1.21  normal • less than 1.20  abnormal
  35. 35. Valsalva manoeuvre • Valsalva maneuver evaluates – 1. sympathetic adrenergic functions using the blood pressure responses – 2. cardiovagal (parasympathetic) functions using the heart rate responses
  36. 36. 4. Cold pressor test • Submerge the hand in ice cold water • This increases – systolic pressure by about 20 mmHg – diastolic pressure by 10 mmHg
  37. 37. Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic neurons Veins Arterioles Ventricles SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  38. 38. Figure 15-21 (1 of 10) Blood Pressure Change in blood pressure Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  39. 39. Figure 15-21 (2 of 10) Blood Pressure Carotid and aortic baroreceptors Change in blood pressure Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  40. 40. Figure 15-21 (3 of 10) Blood Pressure Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  41. 41. Figure 15-21 (4 of 10) Blood Pressure Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  42. 42. Figure 15-21 (5 of 10) Blood Pressure Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic neurons Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  43. 43. Figure 15-21 (6 of 10) Blood Pressure Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic neurons SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  44. 44. Figure 15-21 (7 of 10) Blood Pressure Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic neurons SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  45. 45. Figure 15-21 (8 of 10) Blood Pressure Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic neurons Ventricles SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  46. 46. Figure 15-21 (9 of 10) Blood Pressure Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic neurons Arterioles Ventricles SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  47. 47. Figure 15-21 (10 of 10) Blood Pressure Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic neurons Veins Arterioles Ventricles SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY
  48. 48. Baroreceptor Reflex
  49. 49. Valsalva manoeuvre in diabetic autonomic neuropathy
  50. 50. Other ANS tests in CVS • Head up tilt test (HUT) – Heart rate and BP response • BP Response to standing • BP Response to sustained handgrip • Plasma norepinephrine measured with the subject supine and after a period of standing provides another method of studying adrenergic function
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