(as expected). Also, the measurement of PWV with
the help of the indirect method does not require any
special training. Instead, the operator only needs to
follow simple instructions. We think that after im-
proving the method in compliance with existing med-
ical requirements, the developed PWV measurement
method can be used in clinical practice.
The experiments turned out to give an unexpected
result – an opportunity to measure PWV with the help
of one pneumatic sensor located at only one point. In
essence, it impies that one imaginary sensor is located
next to the aortic arch and the other – a real sensor – is
located in the place, where the easiest measurement of
blood pressure can be provided, e.g. above the radial
artery, as illustrated in Figure 4 A. We should note that
this concept is hardly innovative. There is already an
accepted methodology for measuring PWV with the
help of a combination of the ECG and a plethysmo-
graphic sensor mounted on the patient’s finger. For
details and references to similar methods, please refer
(Bereksi-Reguig et al., 2017), (Castro et al., 2017),
(Proenca et al., 2010), (Liu et al., 2011), (Oreggia
et al., 2015). However, it is worth noting that although
our method is similar to the well-known plethysmo-
graphic approaches, it interprets the measurement of
the transit time T
pwtt
, used to calculate PWV, some-
what differently (see Figure 4 B).
t
P
aort output
Vecg
Tptt
P
art radial
Tpep
Tpwtt
P
aort output
P
art radial
jugular cavity
aortic arch
subclavian
artery
brachial
artery
ulnar artery
radial
artery
Vecg
d
V=
d
(T
ppt
-T
pep
)
d
Figure 4: PWV estimation with only one sensor located at
only one point. (A) imaginary sensor location above the
aortic arch and real sensor location on the wrist. (B) illus-
tration of relations between ECG V
ecg
(t), and blood PWs
P
aortout put
(t), P
artradial
(t) at locations shown in (A).
For exfmple, following their colleagues, the au-
thors of (Bereksi-Reguig et al., 2017) are guided by
the suggestion that the moment when R–peak appears
in the ECG almost matches the moment when the
pulse wave foot starts forming at the aorta output /
at the beginning of the subclavian artery. With that,
the pulse wave transition time T
pwtt
can be taken as
the delay period T
ptt
– pulse transit time (see Fig-
ure 4 B). After that, by dividing d (distance from the
jugular cavity to the finder tip) by the delay period,
PWV will be measured as V = d/T
ptt
. And though
(Bereksi-Reguig et al., 2017) mentions that T
pwtt
dif-
fers from T
ptt
by the pre-ejection period T
pep
(time
between ventricular contraction and beginning of the
formation of the pulse wave at the aorta output, see
Figure 4), the authors consider that difference negli-
gible (T
pep
≪ T
ptt
).
5 PULSE TRANSIT TIME
CORRECTION
However, our study showed that when the blood pres-
sure sensor is installed on the wrist or higher on the
arm, the suggestion T
pep
≪ T
ptt
becomes very in-
accurate or even incorrect. In fact, the authors of
the recent study (Kortekaas and van Velzen, 2018)
provided results of echocardiographic T
pep
measure-
ments for three groups, 20 persons in each, namely:
focus groups with no cardiovascular disorders under
50 years (A), older than 50 years (B), and having car-
diovascular risk factors (hypertension, dyslipidemia,
kidney failure, and diabetes) (C). The results derived
in (Kortekaas and van Velzen, 2018) can be summa-
rized in the following way: T
pep
for groups (A) and
(B) lies in ranges 58.5 ± 13.0 msec and 52.4 ± 11.9
msec, respectively; for (C) within the range 57.6 ±
11.6 msec. By comparing these results with our data
shown in Table 2, where T
ptt
taken as “Mean R–f” for
similar groups comes to 140.5 ± 10.1 msec for (A),
112.1 ± 4.8 msec for (B) and 110.4 ± 5.0 msec for
(C), it is not too hard to figure up that T
pep
represents
a considerable part of T
ptt
(up to half of the latter) in
all groups. In this regard, it is interesting to note that
the aim of the study (Kortekaas and van Velzen, 2018)
was to substantiate the non–obvious assumption, as
we show above, that T
pep
≪ T
ptt
.
For the foregoing reasons, PWV measurement
should employ the correct formula V = d/(T
ptt
−
T
pep
) that contains the pre-ejection period T
pep
. For-
tunately, it is not necessary to calculate T
pep
in ev-
ery case. The abovementioned study (Kortekaas and
van Velzen, 2018) states that T
pep
has weak individual
variations, at least within specific groups (A, B, C) of
patients. This said, having the reference values T
pep
for the corresponding groups and determining the af-
filiation of each patient to one of these groups (for
example, from his electronic health record – EHR),
we can use the proposed method for measuring PWV
only using the pulse transit time T
ptt
, but adjusting it
using the value T
pep
for the corresponding group. The
results of estimating PWV, using the data shown in
Table2, are given in Table 3.
As seen from Table 3, the Pulse Wave Velocity ob-
tained by us with the use of the modified pneumatic
sensor following the simplified indirect PWV mea-
Methods of the Pulse Wave Velocity Estimation based on Pneumatic Blood Pressure Sensor Data and Synchronous ECG Records
305