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Devices and Technology

Validation of the iHealth BP7 wrist blood pressure monitor, for self-measurement, according to the European Society of Hypertension International Protocol revision 2010

Wang, Qing; Zhao, Huadong; Chen, Wan; Li, Ni; Wan, Yi

Author Information
doi: 10.1097/MBP.0000000000000017
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Abstract

Introduction

Self-monitoring of blood pressure (BP) is recommended by several hypertension societies not only at home for daily monitoring but also in clinical practice for the diagnosis and long-term follow-up of hypertension patients 1–3. Furthermore, with the development of telemedicine and related technology, increasingly more wireless devices are being used for monitoring vital signs or controlling of chronic conditions including BP monitoring using wireless BP measurement devices 4,5. The iHealth BP7 wireless wrist BP monitor can measure BP independently and transfer BP data to mobile touchable iOS devices through Bluetooth technology with telemedicine characteristics. In this study, we aimed to validate the iHealth BP7 wireless wrist BP monitor according to the European Society of Hypertension International Protocol (ESH-IP) revision 2010 6.

Materials and methods

Tested device

The iHealth BP7 wireless wrist BP monitor (Andon Health Co. Ltd, Tianjin, China) is an oscillometric device for BP self-measurement that can test, track, and share BP data and pulse rate with a mobile touchable iOS device (iPod touch, iPhone, or iPad with an iOS version V4.3 or higher; Apple Inc., Cupertino, California, USA). Before first use, the battery of the tested device needs to be charged and the iOS device needs to download and install the free ‘iHealth Myvitals’ App from the App Store. The iHealth BP7 performs measurement within a range of 60–260 mmHg for systolic blood pressure (SBP), 40–199 mmHg for diastolic blood pressure (DBP), and 40–180 beats/min for pulse rate. The standard wrist cuff circumference is suitable for a wrist circumference of 13.5–22 cm (Table 1).

Table 1
Table 1:
Device details

An iPod touch (fifth generation) with the iOS version V5.0 and Bluetooth V2.1 was used in the study after installation of the App version V1.1.1 as a data accepter and data manager.

Familiarization

Ten test measurements were carried out and no problems were encountered.

Recruitment

Hypertensive participants were recruited from among inpatients and outpatients in a general hospital. Normotensive participants were recruited from among accompanying relatives or friends and from among hospital staff. Participants on antihypertensive treatment were also recruited and their data were recorded (Table 2).

Table 2
Table 2:
Screening and recruitment details

Procedure

The validation process was performed by two observers, under the supervision of an independent supervisor experienced in BP measurement, who were retrained on mercury BP measurement as per the British Hypertension Society tutorial.

During the measurement, the hand of the participant was placed palm side up and the cuff was wrapped around a bare wrist 1–2 cm above the wrist joint. If the monitor is correctly placed, the iHealth logo will be facing upright. The monitor’s travel case was placed under the arm for support and the arm was maintained at optimal height for measurement. When adjusting the height of the wrist, the App will visually detect wrist position and the measurement will start only when the correct position is detected. Then, the on-screen instructions were followed to take a measurement.

Two standard mercury sphygmomanometers were used as reference sphygmomanometers, the components of which were checked and calibrated carefully before the study. Two cuffs were used for the reference BP measurements: a standard cuff with a bladder width of 12 cm and a length of 24 cm for arm circumferences from 22 to 30 cm and a larger cuff with a bladder width of 12 cm and a length of 34 cm for arm circumferences from 30 to 42 cm, which was based on the recommendations of the British Hypertension Society. All BP measurements were taken on the left arm or the left wrist. The two observers were blinded to each other’s readings and the device readings. The ESH-IP revision 2010 for the validation of BP measurement devices in adults was followed precisely 6.

Results

A total of 47 participants were recruited for inclusion in the study and finally 33 participants were enrolled into the study according to ESH-IP revision 2010 (22 men and 11 women). The mean age of the participants included was 48.5±11.8 years. The study was carried out using the left arm (wrist), arm circumference 26.3±1.9 cm and wrist circumference 16.9±1.7 cm. A standard wrist cuff was used for the range of wrist circumference (fitting wrist circumference between 13.5 and 22 cm). The BP of the participants on recruitment was 140.1±23.7 for SBP and 87.1±16.2 for DBP (Table 3).

Table 3
Table 3:
Participants’ details

During validation, the observer measurements had an overall range of 92–187 mmHg for SBP and 46–121 mmHg for DBP. The distribution of observer measurements into the low, medium, and high BP range fulfilled the requirement of the ESH-IP revision 2010, with observer differences of 0.2±2.3 for SBP and −0.2±2.3 for DBP (Tables 4 and 5).

Table 4
Table 4:
Observer measurements in each recruitment range
Table 5
Table 5:
Observer differences

In part 1 of the validation results, the tested device passed the requirement with 66, 87, and 97 measurements within 5, 10, and 15 mmHg for SBP and 72, 93, and 99 mmHg for DBP, respectively. The mean±SD device–observer difference was −0.7±6.9 mmHg for SBP and −1.0±5.1 mmHg for DBP. Subsequently, the number of participants with two or three of the absolute device–observer differences within 5 mmHg was 25 for SBP and 26 for DBP. Furthermore, there were three participants for SBP and one for DBP with none of the absolute device–observer differences within 5 mmHg (Table 6). The Bland–Altman graphs of device–observer differences versus average device and observer values for the 99 pairs of comparisons are shown in Fig. 1. Thus, the iHealth BP7 passed all the phases of validation, fulfilling the validation criteria of the ESH-IP revision 2010.

Table 6
Table 6:
Validation results
Fig. 1
Fig. 1:
(a) Systolic blood pressure (SBP) and (b) diastolic blood pressure (DBP) differences between the test device and the observer, and the mean pressure of device and observer values.

Discussion

From the validation results, the iHealth BP7 passed all phases of ESH-IP revision 2010 that showed BP measurement accuracy across a wide range of BP for self/home monitoring in the general population. As BP measurements can be affected by the position of the wrist relative to the heart and may also be influenced by flexion or hyperextension of the wrist 7, it is very important to keep the wrist at the level of the heart (the middle of the cuff should be at the level of the right atrium of the heart) during monitoring. In this validation study, through the visualized operation interface of the iOS device, a step-by-step process can guide the user to perform the measurement easily. Furthermore, an interactive visualized figure of arm and wrist positions can be displayed on the screen of iOS device to help the user maintain proper arm and wrist positions, and the device will not measure BP until the arm and wrist positions are acceptable. In practice, users should keep in mind that the hydrostatic pressure generated by a wrong position of the wrist in relation to the heart may lead to incorrect readings.

The iHealth BP7 is a fully automatic device for wrist BP measurement that works with the iOS devices. The device fulfilled the requirement of the ESH validation protocol, passing all phases of the validation study. The average device–observer difference was −0.7 mmHg for SBP and −1.0 mmHg for DBP, which indicated that the device is highly accurate. In addition, variability of accuracy between different participants was good; the SD of the mean difference was no more than 6.9 mmHg.

Conclusion

According to the results of the validation study on the basis of the ESH-IP revision 2010, the iHealth BP7 wrist blood pressure monitor can be recommended for self/home measurement in an adult population. Meanwhile, the correct use of the iHealth BP7 wrist blood pressure monitor according to instructions is important and is recommended to obtain accurate results.

Acknowledgements

The device used in this study was donated by Andon Health Co. Ltd and was chosen at random from the production line. None of the authors has any association with Andon or has received any personal benefit from Andon.

Conflicts of interest

There are no conflicts of interest.

References

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Keywords:

blood pressure; European Society of Hypertension; validation

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