Real- time Detection of Blood Pressure changes
using contact free sensors
Presenting student: Efrat Herbst Instructed by: Zvika Shinar
Methods
Introduction
Results
1) Synchronized signals not filtered, received from the reference BP
device Portapress (in the upper graph) and from EverOn sensors (in
the lower graph) at rest. Chest signal in blue, Pelvic signal in green.
I.
Median ratio between max/min peak to peak amplitude:
Portapress BP signal- not filtered
Separated mattresses
One mattress
1st rest period
1.2564
1.5629
2nd rest period
1.4464
3rd rest period
1.518
Separated mattresses
One mattress
1st rest period
1.6009
1.393
1.2446
2nd rest period
1.7999
1.3567
1.3667
3rd rest period
1.7768
1.3741
BP [mmHg]
150
II. In preliminary calculations, PTT changes were found in the holding
breath protocols: 55 [ms] relative to a 50 [mmHg] change in systolic
BP and 70 [ms] relative to 60 [mmHg]:
100
50
185
186
187
188
189
6
8.4
190
sec
191
192
193
194
195
BP derived from Portapress
Chest & Pelvis signals- not filtered
x 10
180
160
8.39
140
Objectives
8.37
100
80
8.35
185
186
187
188
189
190
sec
191
192
193
194
195
60
4
x 10
0
500
1000
1500
2000
2500
2000
2500
sec
2) Proving that pelvic signal is comprised of: 1. signal generated in the
heart and moved within the mattress to the pelvic sensor and most
important 2. signal generated in the pelvic area of the body.
PTT calculation with average
0.25
0.2
0.15
4
0.1
3
2
0.05
1
0
500
1000
1500
sec
0
-1
Discussion and Conclusions
-2
-3
-4
241.2
241.4
241.6
241.8
242
242.2
242.4
242.6
242.8
I.
243
3) Final experiment
6
9.8
BP signal with max points identifying heartbeats
x 10
9.6
9.4
9.2
9
1529
1530
1531
1532
5
1
1533
1534
1535
1536
1537
1538
1539
1536
1537
1538
1539
1536
1537
1538
1539
Chest signal with minmax points
x 10
0.5
0
-0.5
 To prove that signals are transmitted through the mattress
and thus signal detected in each sensor is the superposition
of the signal generated by the blood stream above the sensor
with signal generated somewhere else and was
Transmitted to the sensor through the mattress.
Examining whether PTT can be measured using
two EverOn sensors, placed under different locations of the body.
120
8.36
sec
• Usually, the interval between the peak of the R-wave on the ECG and the
onset of the corresponding pulse in the finger pad measured by PPG is
defined as the PTT.
• However, there is a considerable
delay between the electrical
cardiac activity (R-peak) and the
mechanical ventricular ejection.
This delay is referred to as the
Pre-Ejection Period (PEP).
The PEP is affected by
pathologies, drugs and other
factors, and therefore can cause
impreciseness in the PTT
measurement, and in the PTT-BP
correlation.
• Ballistocardiography (BCG) is the
recording of the movements of the
body caused by shifts in the center
mass of blood in the arterial system
and, to a lesser extent, of the heart,
caused by cardiac contraction.
[mmHg]
8.38
-1
1529
1530
1531
1532
1533
1530
1531
1532
1533
4
4
x 10
1534
1535
sec
Pelvis signal with minmax points
2
0
-2
-4
1529
1534
sec
1535
Identifying the beat that arrives the pelvic area is critical. If we had
found that the signal received in the pelvic sensor is composed only
by the chest signal transferred through the mattress, we had no
point in continue this research. In our experiments we saw that
signal generated by the pelvic area can be isolated and thus method
is applicable.
II. As predicted, Change of PTT was found when BP changed. The
relative is of 1.1 [ms] to 1[mmHg].
III. It seems that hand gripping for 5 minutes in order to change BP
caused trembling of the hand, which makes it more difficult to find
the heart beats and thus analyze the PTT.
IV. To the future, it is
important to create a
system that has the
same clock sampler
for all sensors,
because of the
importance of synchronized signals to the extent of a single heart
beat.