Validation of the Omron 637IT wrist blood pressure measuring device with a position sensor according to the International Protocol in the elderly.

Abstract

The market for wrist devices for self-measurement is growing and these devices are becoming popular among the patients. Despite widespread use of these devices, there is limited published evidence for their accuracy and reliability in the different patient groups. The objective of this study was to evaluate the accuracy of the Omron 637IT (Omron Healthcare Europe B.V, Hoofddorp, Netherlands) wrist blood pressure device against the mercury sphygmomanometer in the elderly according to the International Protocol criteria.
Seventy-six patients older than 65 years of age were studied and classified on the basis of the range of the International Protocol. Blood pressure measurements at the wrist with the Omron 637IT were compared with the results obtained by two trained observers using a mercury sphygmomanometer. Nine sequential blood pressure measurements were taken. A total of 33 participants with arm circumference distributed randomly were selected for the validation study. During the validation study, 99 measurements were obtained for comparison in the 33 participants. The first phase was performed on 15 participants, and if the device passed this phase, 18 more participants were selected.
Mean discrepancies and standard deviations of the sphygmomanometer device were -0.3+/-6.5 mmHg for systolic blood pressure and 2.8+/-4.8 mmHg for diastolic blood pressure in the study group. The device passed phase 1 in 15 participants. In phase 2.1, from the total 99 comparisons, 66, 87, and 95 for systolic blood pressure and 69, 92, and 97 for diastolic blood pressure were <5, <10, and <15 mmHg, respectively. In phase 2.2, 24 participants had at least two of the differences within 5 mmHg and three participants had no differences within 5 mmHg for systolic blood pressure. For diastolic blood pressure, 24 participants had at least two of the differences within 5 mmHg and three participants had no differences within 5 mmHg. The Omron 637 IT passed the phase 2.1 and 2.2 in the elderly group.
The Omron 637IT wrist blood pressure device passed according to the International Protocol criteria and can be recommended for use in the elderly.

Full text

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Devices and technology97
Validation of the Omron 637IT wrist blood pressure
measuring device with a position sensor according to the
International Protocol in the elderly
S¸ekip Altunkan and Erkan Altunkan
Objective The market for wrist devices for self-measure-
ment is growing and these devices are becoming popular
among the patients. Despite widespread use of these
devices, there is limited published evidence for their
accuracy and reliability in the different patient groups. The
objective of this study was to evaluate the accuracy of the
Omron 637IT (Omron Healthcare Europe B.V, Hoofddorp,
Netherlands) wrist blood pressure device against the
mercury sphygmomanometer in the elderly according to
the International Protocol criteria.
Methods Seventy-six patients older than 65 years of age
were studied and classified on the basis of the range of the
International Protocol. Blood pressure measurements at
the wrist with the Omron 637IT were compared with the
results obtained by two trained observers using a mercury
sphygmomanometer. Nine sequential blood pressure
measurements were taken. A total of 33 participants with
arm circumference distributed randomly were selected for
the validation study. During the validation study, 99
measurements were obtained for comparison in the 33
participants. The first phase was performed on 15
participants, and if the device passed this phase, 18 more
participants were selected.
Results Mean discrepancies and standard deviations of the
sphygmomanometer device were –0.3±6.5mmHg for
systolic blood pressure and 2.8±4.8mmHg for diastolic
blood pressure in the study group. The device passed
phase 1 in 15 participants. In phase 2.1, from the total 99
comparisons, 66, 87, and 95 for systolic blood pressure and
69, 92, and 97 for diastolic blood pressure were <5, <10,
and <15mmHg, respectively. In phase 2.2, 24 participants
had at least two of the differences within 5mmHg and
three participants had no differences within 5mmHg for
systolic blood pressure. For diastolic blood pressure, 24
participants had at least two of the differences within
5mmHg and three participants had no differences within
5mmHg. The Omron 637 ITpassed the phase 2.1 and 2.2 in
the elderly group.
Conclusion The Omron 637IT wrist blood pressure device
passed according to the International Protocol criteria and
can be recommended for use in the elderly. Blood Press
Monit 11:97–102? c 2006 Lippincott Williams & Wilkins.
Blood Pressure Monitoring 2006, 11:97–102
Keywords: blood pressure measurement, elderly, Omron 637IT, validation,
wrist monitors
Hypertension Division, Metropol Medical Center, Ankara, Turkey
Correspondence and requests for reprints to Dr S¸ekip Altunkan, Metropol
Medical Center, Nisan Sokak, No. 7, 06400 Dikmen, Ankara, Turkey
Fax: +90(312)4831656; e-mail: saltunkan@veezy.com
Received 12 May 2005 Revised 24 October 2005
Accepted 7 November 2005
Introduction
Blood pressure is one of the most important indicators
of future cardiovascular risk [1]. Aging increases the
importance of high blood pressure even more. In parallel
to the increase in other risk factors, the prevalence
of cardiovascular diseases in elderly people increases
depending on the level of blood pressure [2].
The correct measurement of blood pressure at all ages is
very important in determining high blood pressure levels.
The Riva Rocci/Korotkoff method, which has been used
for more than 100 years, has constituted the basis
for many studies on hypertension [3]. Recently the
development of devices measuring blood pressure for 24h
has caused the white-coat effect to become prominent.
That white-coat hypertension is common in elderly
patients is well known [4]. Furthermore, the prevalence
of postural hypotension is high in these patients and this
may cause undesirable clinical consequences at times [5].
Ambulatory blood pressure monitors should be used to
investigate the white-coat effect in elderly patients and
to determine postural hypotension [4]. As a result of the
high cost of this monitoring and difficulties in its
continuous application, it is of great importance for the
patients to be able to self-measure their own blood
pressure. Furthermore, to follow the efficiency of the
therapy and to adjust the drug doses, elderly patients
should be encouraged to self-measure their own blood
pressure at home [6].
Automatic devices are widely used by patients to self-
measure their own blood pressure. The accuracy of the
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measurement values produced by this equipment should,
however, be investigated through clinical studies [7]. The
use of devices measuring blood pressure at the wrist is
quite common today among patients and is becoming
more popular daily [8]. These devices need to be
validated on different patient groups. To the authors
knowledge, no studies in which these devices have been
tested for elderly patients exist. In our present study, we
aimed to investigate the accuracy and reliability of a
device measuring blood pressure at the wrist, the Omron
637IT (Omron Healthcare Europe B.V., Hoofddorp, The
Netherlands), in elderly patients, according to the
International Protocol rules [9].
Methods
Subjects
Seventy-six patients older than 65 years of age were
included in this study. Among these patients, individuals
whose blood pressure was not within the range set by the
International Protocol, those with arrhythmia and known
heart disease, peripheral artery disease, and who de-
scribed typical angina pectoris were excluded from the
study. Patients were investigated for pseudohypertension.
To this end, following occlusion of the brachial artery by
cuff, those with a palpable radial artery were considered
as pseudohypertensive (those patients positive for Osler’s
sign) and were excluded from the study [10]. Each
participant provided informed consent for the study,
which was approved by the Institutional Review Board.
Thirty-three participants were recruited for each valida-
tion study all with the range of blood pressure required
by the International Protocol rules, in each BP category,
having blood pressure less than 130/80mmHg (11 parti-
cipants), between 130–160 and 80–100mmHg (11
participants) and higher than 160/100mmHg (11 parti-
cipants) for the elderly group (Table 1). Participants with
a wrist circumference of less than 145mm were excluded
from the study. Demographic data including age, sex,
height, weight, pre-existing diseases, arm, and wrist
circumference were recorded. Arm circumferences of
the study group were distributed by chance.
Instruments
The Omron 637IT is a compact fully automatic wrist
blood pressure monitor. Operating on the oscillometric
principle, it measures blood pressure and pulse rate from
the wrist. It contains an intelligent system for ‘fuzzy’
controlled inflation, known as ‘intellisens’. This is an
advanced oscillometric measurement. The Omron 637IT
has a position sensor, which is able to determine the
optimal height of the wrist (heart level) for blood
pressure measurement (Instruction Manual 637IT, Vers.
01/07/02). The instrument’s weight is approximately
150g (not including batteries). The functioning of the
position sensor is on the basis of the measurement of the
arm’s angle. During BP measurement, when the position
of the arm is altered, the device stops measuring BP. So
the device carries out the function of measuring blood
pressure while detecting both position and movement. As
it is difficult to estimate the relative vertical distance
between the heart and wrist, finding a universal way to
sense position is challenging, particularly in obese
patients. The Omron company claims to have solved this
problem with the help of software employing an advanced
algorithm, which not only uses the angle of the forearm,
but also compensates for the body angle by using the
bi-dimensional acceleration signal [11].
The sphygmomanometer (Rudolf Riester GmbH & Co.,
Jungingen, Germany) was used as a standard wall-
mounted mercury sphygmomanometer. Appropriate-sized
Velcro cuffs were used during all measurements. The
length of the bladder was always 80% or more than the
circumference, and the cuff covered a minimum of two-
thirds of the upper arm length. A dual-headed binaural
stethoscope (Rudolf Riester GmbH & Co.) was used
during the measurements.
Observer training and assessment
Two observers participated in this study as ‘observers 1
and 2’ and one clinician as an expert having extensive
experience. Observers were trained using web-based
information available on the Internet and specifically
developed by the British Hypertension Society [12].
Procedures
Each participant was seen individually in a quiet,
temperature-controlled examination room followed by
waiting in a relaxed atmosphere for a minimum of 5 min.
After a brief history was taken, the blood pressure of each
participant was first measured with the mercury sphyg-
momanometers using the same (left) arm by observers
1 and 2 for the subgroup analysis. The mean values were
used to categorize the participant according to the
International Protocol. Then, blood pressure was mea-
sured to allow the device to determine the blood pressure
characteristics of the participants by observer 3 before the
actual measurements were taken. The device validation
was carried out using the sequential same-arm by two
trained, blinded observers alternating between the
mercury sphygmomanometer and the device, with the
participant in the sitting position. The device measure-
ment was taken by observer 3 with reference to the
instruction manual of the Omron device and with the
wrist position sensor on. The trained observers (observers
Table 1
Protocol
Blood pressure ranges according to the International
Systolic BPDiastolic BP
Low
Medium
High
90–129
130–160
161–180
40–79
80–100
101–130
BP, blood pressure.
98
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2006, Vol 11 No 2
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Page 3

1 and 2) and observer 3 sequentially performed seven
blood pressure measurements (four using the mercury
sphygmomanometer and three using the device) for each
subject. At least 30s was allowed between each
measurement to avoid venous congestion, but not more
than 60s, to minimize variability in blood pressure.
Measurements made simultaneously by observers 1 and 2
were checked by observer 3. If the systolic and diastolic
measurements were more than 4mmHg apart, the
measurement was taken again. A total of nine sequential
same-arm measurements between the device and a
mercury sphygmomanometer were taken as follows:
BPA: The mean value was used to categorize the
participants into low, medium or high blood pressure
ranges for both systolic blood pressure (SBP) and
diastolic blood pressure (DBP).
BPB: Measurement was made by observer 3 to permit the
device to determine the blood pressure characteristics of
the participant.
BP1, BP3, BP5, and BP7 were recorded by observers 1
and 2 with the mercury sphygmomanometer.
BP2, BP4, and BP6 were recorded by observer 3 with the
Omron 637IT.
Analysis
Discrepancy analysis and Bland–Altman plots were
undertaken using the VAPA software package (Version
1.4.8–2003) developed by the Group for Blood Pressure
Measurement and Evaluation (French Society of Hyper-
tension). Only measurements BP1–BP7 were used to
assess accuracy. The percentage of observer and the test
device measurements within 5, 10, and 15mmHg of each
other were determined separately for SBP and DBP. The
mean of each pair of observer measurements was
calculated and denoted as observer measurement BP1,
BP3,BP5, andBP7. The
BP2–BP3, BP4–BP3, BP4–BP5 and BP6–BP7 were
then calculated. The absolute values of these differences
were derived; if the values in a pair were unequal, the
observer measurement corresponding to the smaller
differences was used. When the values in a pair were
equal, the first of the observer measurements was used.
differencesBP2–BP1,
The discrepancies were calculated according to the
criteria of the International Protocol. In phase 1, three
pairs of measurements were performed on 15 partici-
pants, five participants in each of the BP categories. If the
45 comparisons reached at least the set criteria, further
evaluation analysis was to be performed on 18 partici-
pants. To consider the device accurate, the 45 compar-
isons in phase 1 must reach one of the following (at least
25 or more <5mmHg, 35 or more <10mmHg, and 40
or more <15mmHg). Phase 2 determines how accurate
the device will be for individual measurements (phase
2.1) and for individual participants (phase 2.2). To pass
phase 2.1, a device had to have at least 60 of 99
measurements within 5mmHg, 75 within 10mmHg, and
90 within 15mmHg. Furthermore, there had to be a
minimum of either 65 comparisons within 5mmHg and
80 within 10mmHg, or 65 comparisons within 5mmHg
and 95 comparisons within 15mmHg, or 80 comparisons
within 10mmHg and 95 comparisons within 15mmHg.
To pass phase 2.2, at least 22 of the 33 participants had to
have at least two of their three device measurements
within 5mmHg (these include those who have all three
comparisons within 5mmHg). At most, three of the 33
participants had to have all three of their comparisons
over 5mmHg apart.
Results
The mean age was 72±5 years (range 65–80 years). The
study population comprised 16 men and 17 women.
The mean body mass index, upper arm circumference
and wrist circumference were 29±5kg/m2(range 25–
37kg/m2), 31±5cm (range 25–38cm) and 19±3cm
(range 17–23cm), respectively. The mean blood pres-
sures were 146±23mmHg (range 104–180mmHg) for
SBP and 86±16mmHg (range 62–112mmHg) for DBP.
Results are reported in Table 2.
A total of 31, 41, and 43 of SBP and 29, 43, and 45 of DBP
readings at phase 1 were within 5, 10, and 15mmHg,
respectively, of the mercury standard. The device passed
the requirements of phase 1 in the elderly group (Table
3). In phase 2.1, from the total 99 comparisons, 66, 87,
and 95 for SBP and 69, 92, and 97 for DBP were <5,
<10, and <15mmHg, respectively. Twenty-four parti-
cipants had at least two of the differences within 5mmHg
and three participants had no differences within 5mmHg
for SBP, and 24 participants had at least two of the
differences within 5mmHg and three participants had no
differences within 5mmHg for DBP. The mean differ-
ences between the measurements of the device and
observers were –0.3±6.5 and 2.8±4.8mmHg for SBP
and DBP, respectively. The Omron 637IT passed both
phases 2.1 and 2.2 (Table 3).
Table 2
Participant characteristics of the study group
Characteristics Mean±SD
Age (years)
Men/women
BMI (kg/m2)
Arm circumference (cm)
Arm wrist circumference (cm)
Systolic blood pressure (mmHg)
Diastolic blood pressure (mmHg)
72±5
16/17
29±5
31±5
19±3
146±23
86±16
BMI, body mass index.
Validation of the Omron Altunkan and Altunkan99
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Page 4

Bland–Altman [13] plots of pressure differences plotted
against the observer are shown in Figs 1 and 2 for SBPand
DBP, respectively.
Discussion
Measurement of blood pressure at home is both a feasible
and valuable method in the follow-up of blood pressure
[14]. Yet, there are debates as to which method should be
used in measuring blood pressure at home [15].
Measurements with the auscultatory method especially
in the elderly group do not always yield accurate results.
The use of a mercury sphygmomanometer at home is not
recommended because of its toxic effects on the
environment [16]. Aneroid equipment, on the other
hand, can be difficult to use at home, as they malfunction
frequently, need frequent calibration, and as hearing
problems increase with age [17,18]. Electronic blood
pressure measurement devices developed in recent years
are commonly used in patient follow-up. These devices
measure blood pressure at either the upper arm or the
wrist. Validation studies, however, are needed with regard
to electronic equipment. The number of clinically
approved devices among those sold in the market is
quite few [7].
Electronic blood pressure measurement devices perform
measurements with the oscillometric method [19].
Measurement of blood pressure in elderly patients may
have some special dimensions. Structural changes may be
observed in the aorta and wide arteries throughout the
course of aging. The most significant structural change is
the hardening of these arteries. As artery hardening
(artherosclerosis) develops, the compliance of vessels
Table 3
Accuracy of the Omron 637 IT device analyzed according to the International Protocol in the elderly subjects
Phase 1Within 5mmHgWithin 10mmHg Within 15mmHgRecommendation
Required
Achieved
One of
SBP
DBP
25
31
29
35
41
43
40
43
45
Continue
Continue
Phase 2.1 Within 5mmHgWithin 10mmHgWithin 15mmHgRecommendationMean differenceStandard deviation
RequiredTwo of
All of
SBP
DBP
65
60
66
69
80
75
87
92
95
90
95
97
AchievedPass
Pass
–0.3mmHg
2.8mmHg
6.5mmHg
4.8mmHg
Phase 2.22/3 within 5mmHg 0/3 within 5mmHg Recommendation
Required
Achieved
Z22
24
24
r3
SBP
DBP
3
3
Pass
Pass
SBP, systolic blood pressure: DBP, diastolic blood pressure.
Fig. 1
80
30
25
20
15
10
5
0
−5
−10
−15
−20
−25
−30
90 100 110 120 130 140 150 160 170 180 190
Mean device and observer (mmHg)
Difference SBP device-observer
Device-observer (mmHg)
Bland–Altman plot of systolic blood pressure (SBP) for the Omron
637IT in the elderly participants. The 99 comparisons are presented as
pressure difference (device–observer) against the mean pressure
(device and observer).
Fig. 2
80 706050 403090
Difference DBP device-observer
100 110 120 130 140
Mean device and observer (mmHg)
30
25
20
15
10
5
0
−5
−10
−15
−20
−25
−30
Device-observer (mmHg)
Bland–Altman plot of diastolic blood pressure (DBP) for the Omron
637IT in the elderly participants. The 99 comparisons are presented as
pressure difference (device–observer) against the mean pressure
(device and observer).
100
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2006, Vol 11 No 2
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Page 5

decreases. The oscillations occuring in the arteries may
be influenced by the decreased compliance of arteries,
which may cause automatic devices to misread blood
pressures. As the structural characteristics of the vessel
walls are quite heterogeneous in different vessel regions,
stiffness in the arm artery does not necessarily accompany
stiffness in the other body arteries [20]. Several direct
and indirect methods are utilized to identify the
mechanical characteristics of the artery wall. Some of
the direct measurement methods, however, are invasive,
some are expensive, and some are poorly correlated with
clinical findings and difficult to apply [21]. A significant
amount of the indirect measuring methods are based on
pulsewave reflection and distortion [22]. Atherosclerotic
lesions can affect the level of the pressure to varying
degrees. There are only few studies on how those vessel
wall changes that are diagnosed using indirect methods
affect blood pressure measurement methods. The patient
groups, in whom vessel stiffness is most frequently
encountered, are the elderly and diabetics. In two
research studies held in such groups, the significance of
the oscillometric method in blood pressure measurement
was investigated. In the study on elderly patients, the
oscillometric method was compared with the random zero
sphygmomanometer, and it was concluded that in
patients with vessel stiffness, the oscillometric system
revealed a higher measure for the SBP and DBP [23]. A
totally different result was achieved in patients with
diabetes [24]. In this study, SBP measured with the
oscillometric method was found to be higher for lower
blood pressure values and lower for higher blood pressure
values. DBP measured by the oscillometric method was
found to be lower in diabetic patients. Obviously
different results were obtained in these two studies.
Both studies used the auscultatory method as reference
values. Furthermore, there are views that the hardening
in the arterial wall may affect the measurements by the
auscultatory method [25]. Further studies are needed
regarding the effects of vessel stiffness on blood pressure
measurement methods.
In this study, the Omron 637IT, an equipment measuring
blood pressure from the wrist, was clinically tested
according to the rules of the International Protocol, and
found to be reliable and valuable in elderly patients. This
equipment does not perform measurements if the
equipment is not at the same level with the heart, when
the position sensor key is open. Comments exist
regarding the use of these devices that it is important
to keep them at the same level with the heart and that
correct measurements can only be performed this way. It
is also claimed that when they are not kept at the same
level with the heart, they can perform false measure-
ments because of the hydrostatic pressure formed [26].
Nolly et al. [27] have obtained quite reliable results with a
Braun 2550, a model measuring blood pressure at the
wrist, which performs measurements at the level of the
heart. Yarows [28] has shown that Omron 637 performed
measurements that are more accurate when the position
sensor was open as compared with when it was closed.
Another contrary view against the use of equipment
performing measurements at the wrist is that the
hardening in the vessel walls in radial and ulnar arteries
may lead to false measurements [8]. No strong evidence,
however, exists that the atherosclerotic changes in the
vessel wall increase towards the distal arm [22].
Elderly patients constitute an important part of the
hypertensive patient population, and these patients differ
from the other patient groups in certain characteristics.
Isolated systolic hypertension and arrhythmia prevalence
in these patients is quite high [2]. In our study group as
well the number of patients with isolated systolic
hypertension was particularly quite high, and these
patients were excluded from the study. As is well known,
in the measurements with the oscillometric method, the
maximum oscillation point within the cuff is determined
(mean arterial pressure) and the SBP and DBP are
calculated with the help of a special algorithm on this
point [19]. Pannarale et al. [29] have pointed out that in
patients with wide pulse pressure, it might be difficult for
the present algorithm in the devices to calculate the SBP
and DBP away from the measured mean blood pressure.
Although they assert that their view in this study was
speculative, we evaluate it as a view to be considered and
investigated. This situation may point to a problem in all
oscillometric equipment. In addition, in validation
protocols, it is not clear into which blood pressure
category the patients with isolated systolic hypertension
or wide pulse pressure should be included. In patients
with a wide pressure range, it is necessary to define both
the blood pressure ranges and the validation criteria. We
hope that this would be considered in the blood pressure
measurement meetings of the hypertension society.
As a result, 637IT, which is a position sensor model of
Omron measuring at the wrist, can be used reliably in the
follow-up of blood pressure in elderly patients. When
elderly patients, however, have any limitations or cannot
do take the readings for themselves, such measurements
should be made with assistance from a second person. On
the other hand, we believe that use of these devices
should also be investigated in patients with confirmed
arteriosclerosis and in those with isolated systolic
hypertension and arrhythmia.
References
1 World Health Organization. International Society of Hypertension Writing
Group. 2003 World Health Organization (WHO)/International Society of
Hypertension (ISH) statement on the management of hypertension.
J Hypertens 2003; 21:1983–1992.
2Meeks WM. Pathophysiology of hypertension in the elderly. Semin Nephrol
2002; 22:65–70.
3Pickering TG. Principles and techniques of blood pressure measurement.
Cardiol Clin 2002; 20:207–223.
Validation of the Omron Altunkan and Altunkan101
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