Photoplethysmographic blood presure measurement/ Department of Physiology
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Photoplethysmographic
blood presure measurement
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Peňáz´s method,
volume-clamp method

Photoplethysmographic blood presure measurement/ Department of Physiology
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Principle of continual blood pressure measurement
Arterial lumen (finger volume)
Pressure in the cuff
Control system
Constant finger volume
pressure
Before application of control system
Control system:
Correction of the pressure in the finger cuff according to the arterial lumen changes.
Aim: maintaining of constant arterial lumen through pressure changes in the cuff.
application of control system
cuff

Photoplethysmographic blood presure measurement/ Department of Physiology
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SBP
DBP
150/90
127/92

Photoplethysmographic blood presure measurement/ Department of Physiology
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Extrasystoles
supraventricular
ventricular

Photoplethysmographic blood presure measurement/ Department of Physiology
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Orthostatic hypotension

6
Valsalva manoeuvre


See videos:
oscilometric method of BP measurement
https://www.youtube.com/watch?v=Y-NvovSaWTc&t=113s
BP changes during smoking
https://www.youtube.com/watch?v=J5vPJPfNH3k&t=1s

Baroreflex
Fast regulation of arterial blood pressure by changes of heart rate and peripheral vascular
resistance
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peripheral (vascular, sympathetic) branch of baroreflexu
Cardiac (parasympathetic) branch
Baroreflex
heart
signal: heart rate
arteries
signal: blood pressure
resistance arteries
signal: peripheral resistance
CNS: vasomotor centre
CNS: kardiomotor centre

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Baroreflex sensitivity, BRS
RR interval
BRS:
slope
SBP
R
ECG
BRSf:
slope
SBP
SBP
Blood pressure
DBP
BRS: change of cardiac cycle caused by SBP change by 1 mmHg [ms/mmHg]
Evaluation of cardiac baroreflex function through SBP and heart rate (cardiac cycle) changes

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Evaluation of BRS
Standard(oxford) method:
- Application of phenylephrine (vasoconstrictor)
E7C22FD0
normal BRS
STK
STK
decreased BRS

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•Physiologically
•psychic stress – increased sympathetic activity
•Physical exercise  –  increased sympathetic activity
•In old age
•
•Pathologically
•hypertension – decreased baroreceptor sensitivity (atherosclerosis, increased arterial stiffness)
•diabetes – neuropathy of autonomic nervous system
•Chronic depression (neurogenic)
•Heart insufficiency/failure – heart do not response
•Transplanted heart - denervation
•Myocardial infarction – heart do not response
Decreased BRS

Signal: time series
Beat to beat (for example 5 minutes)
•RR interval:                  805, 820, 815, 817, 822, 816,….. ms
•Hear rate:       70, 73, 68, 65, 67, 71,….. bpm
•Systolic blood pressure:         115, 117, 120, 116, 121, 119,….. mmHg
700
800
900
110
120
130
20
40
60
80
100
120 s
RR interval
R
ECG
SBP
Blood pressure
DBP

Frequency domain methods – spectral analysis
Spectrum
Signal in frequency domain
Time series
Signal in time domain
Signal is decomposed in individual frequencies
time (s)
50
40
30
20
0
10
0.5
0.4
0.3
0.2
0
0.1
frequency (Hz)

Spectrum
Signal in frequency domain
Time series
Signal in time domain
Signal is decomposed in individual frequencies
time (s)
50
40
30
20
0
10
0.5
0.4
0.3
0.2
0
0.1
frequency (Hz)
Frequency domain methods – spectral analysis

time (s)
frequency (Hz)
T=50 s
T=10 s
T=3 s
a=0.5
a=0.3
a=0.2
period  T
amplitude  a
frequency  f = 1/T
f = 1/3 = 0.33 Hz
f = 1/10 = 0.1 Hz
f = 1/50 = 0.02 Hz
0.5
0.2
0.3
+
+
=
+
+
=
0.5
0.2
0.3
0.33
0.02
0.1
f = 0,02 Hz
f = 0,1 Hz
f = 0,33 Hz
Spectrum
Frequency domain
Time domain
How the spectrum is formed?

Physiological significance – frequency bands
High frequency (HF)
Intrathoracal pressure changes influencing blood pressure
Very low frequency (VLF)
Low frequency (LF)
Slow hormonal changes, RAS, changes of vascular tonus
Respiratory sinus arrhythmia
baroreflex
band:
baroreflex
0.5
0.4
0.3
0
0.1
0.2
0
0,04
0,08
0,12
0
0,0
0,2
Variability source: respiration
Variability source:

High frequency (HF)
Intrathoracic pressure changes influencing blood pressure
Very low frequency (VLF)
Low frequency (LF)
Respiratory sinus arrhythmia
baroreflex
band:
baroreflex
0.5
0.4
0.3
0
0.1
0.2
0
0,04
0,08
0,12
0
0,0
0,2
parasympathetic activity
Time lag < 1 s
Time lag > 6 s
Slow oscillations
Fast oscillations

High frequency (HF)
Very low frequency (VLF)
Low frequency (LF)
band:
0.5
0.4
0.3
0
0.1
0.2
0
0,04
0,08
0,12
0
0,0
0,2
parasympathetic activity
Time lag < 1 s
Time lag > 6 s
Slow oscillations
fast oscillations
CNS (n. vagus)
Thoracic pressure changes
Changes of TPR
(sympathetic nerves)

Blood pressure signal (270 s)
time (s)
Sitting, paced breathing
Standing, paced breathing
Meyer waves (10 s rhythm)
respiration

sequentions of SBP, DBP and inter-beat intervals
time (s)
Sitting, paced breathing
Standing, paced breathing

Spectra of SBP and IBI
Sitting, paced breathing
Standing, paced breathing
0,1 Hz
Sympathetic activity
Respiratory frequency
vagal activity
↓symp. act., ↑vagal act.
↑ symp. act., ↓vagal act.
frequency (Hz)

Coherence a BRS
frequency (Hz)
Sitting, paced breathing
Standing, paced breathing
0,1 Hz
baroreflex
Respiratory frequency
coherence: synchronization between signals (correlation on particular frequency)

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