Photoplethysmographic blood presure measurement/ Department of Physiology 1
Photoplethysmographic
blood presure measurement
Peňáz´s method,
volume-clamp
method
Photoplethysmographic blood presure measurement/ Department of Physiology 2
Principle of continual blood pressure
measurement
Arterial lumen
(finger volume)
Pressure
in the cuff
Control
systemConstant 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 3
SBP
DBP
150/90
127/92
Photoplethysmographic blood presure measurement/ Department of Physiology 4
Extrasystoles
supraventricular ventricular
Photoplethysmographic blood presure measurement/ Department of Physiology 5
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
8
Baroreflex sensitivity, BRS
RR interval
BRS:
slope
RR
SBP
R
ECG
HR
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
9
Evaluation of BRS
Standard(oxford) method:
- Application of phenylephrine
(vasoconstrictor)
normal
BRSRR
STK
RR
STK
decreased
BRS
• 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
SBP
[mmHg]
RR
[ms]
700
800
900
110
120
130
20 40 60 80 100 120 s
RR interval
R
ECG
SBP
Blood
pressur
e
DBP
Frequency domain methods – spectral analysis
Spectrum
Signal in frequency domain
Time series
Signal in time domain
Signal is decomposed in individual frequencies
amplitude
time (s)
504030200 10 0.
5
0.
4
0.
3
0.
2
0 0.
1
amplitude
frequency (Hz)
Spectrum
Signal in frequency domain
Time series
Signal in time domain
Signal is decomposed in individual frequencies
amplitude
time (s)
504030200 10 0.
5
0.
4
0.
3
0.
2
0 0.
1
amplitude
frequency (Hz)
Frequency domain methods – spectral analysis
amplitude
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
0.330.02 0.1
f = 0,02 Hzf = 0,1 Hzf = 0,33 Hz
Spectrum
Frequency domainTime domain
How the spectrum is formed?
Blood pressure signal (270 s)
time (s)
Bloodpressure
(mmHg)
Krevnítlak(mmHg)
Sitting, paced breathing
Standing, paced breathing
Meyer waves (10 s rhythm)
respiration
sequentions of SBP, DBP and inter-beat intervals
time (s)
BP
(mmHg)
Sitting, paced breathing
Standing, paced breathing
IBI(ms)
BP
(mmHg)IBI(ms)
Spectra of SBP and IBI
SBP
Sitting, paced
breathing
Standing, paced breathing
0,1 Hz
Sympathetic activity
Respiratory frequency
vagal activity
IBI
↓symp. act., ↑vagal act.
↑ symp. act., ↓vagal act.
frequency (Hz)
SBPIBI
Coherence a BRS
frequency (Hz)
Sitting, paced breathing
Standing, paced breathing
coherence
BRS
(ms/mmHg)
coherence
BRS
(ms/mmHg)
0,1 Hz
baroreflex
Respiratory
frequency
coherence: synchronization
between signals (correlation
on particular frequency)
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
Systolicblood
pressure
Heartrate
0.50.40.30 0.1 0.2
0
0,04
0,08
0,12
0
0,0
0,2
SpectrumSBP(n.u.)SpectrumHR(n.u.)
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
Systolicblood
pressure
Heartrate
0.50.40.30 0.1 0.2
0
0,04
0,08
0,12
0
0,0
0,2
SpectrumSBP(n.u.)SpectrumHR(n.u.)
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:
Systolicblood
pressure
Heartrate
0.50.40.30 0.1 0.2
0
0,04
0,08
0,12
0
0,0
0,2
SpectrumSBP(n.u.)SpectrumHR(n.u.)
parasympathetic activity
Time lag < 1 s
Time lag > 6 s
Slow oscillations
fast oscillations
baroreflex
Mechanical
transfer
CNS (n. vagus)
Thoracic
pressure
changes
Changes of TPR
(sympathetic
nerves)
???