Validation of the U60EH Wrist Electronic Blood Pressure Monitor in general population according to the ISO 81060-2:2018/AMD 1:2020 Protocol

Abstract

Objective

To evaluate the accuracy of the U60EH Wrist Electronic Blood Pressure Monitor in general population according to the Universal Standard (ISO 81060-2:2018/AMD 1:2020).

Methods

Subjects were recruited to fulfill the age, gender, blood pressure (BP) and cuff distribution criteria of the Universal Standard in a general population using the same arm sequential BP measurement method. A single cuff for wrist sizes 13.5–21.5 cm was used on this test device.

Results

According to Criterion 1, the mean difference of SBP between the test device and the reference device was 1.51 mmHg, with an SD of 6.48 mmHg. The mean difference of DBP was −0.44 mmHg, with an SD of 5.98 mmHg. The mean difference of both SBP and DBP was less than 5 mmHg, and the SD was less than 8 mmHg, which met the requirements. According to Criterion 2, the mean difference of SBP between the test device and the reference device was 1.51 mmHg, and the SD was 5.88 mmHg, which was less than 6.78 mmHg and met the requirements. The mean difference of DBP was −0.44 mmHg, and the SD was 5.22 mmHg, which was less than 6.93 mmHg and met the requirements.

Conclusion

All results passed the Standard (ISO 81060-2:2018/AMD 1:2020) requirements. The U60EH Wrist Electronic Blood Pressure Monitor can be recommended for home and clinical use.

Introduction

The use of an wrist electronic blood pressure (BP) monitor for BP monitoring is widely accepted. It is convenient to operate and easy to carry. Furthermore, accurate measurement of the BP is crucial for the diagnosis and follow-up of hypertensive patients [1]. This study aimed to determine the accuracy of the U60EH Wrist Electronic Blood Pressure Monitor developed by Shenzhen Urion Technology Co., Ltd. according to the ISO 81060-2:2018/AMD 1:2020 protocol [2].

Methods

Participants

According to the ISO Universal Standard, for a general population validation study of a BP monitor at least 85 subjects aged >12 years are required. The study protocol was approved by the hospital scientific committee of the Second Affiliated Hospital of Nanhua University (Hengyang, China). Subjects were recruited from May to June 2022, and all participants agreed to participate in the protocol and provided written informed consent.

Test device

The U60EH is an automated oscillometric wrist electronic BP monitor developed for home and clinic BP monitoring. The device has a pressure sensor designed to measure BP values during deflation and pulse rate (PR), with an SBP range of 50–255 mmHg, DBP range of 30–200 mmHg and PR range of 40–199 beats per min. Adaptive signal amplification technology was adopted to cover different signal strengths of the tested subjects. The declared degree of precision is ±3 mmHg for BP. A total of 2 × 90 sets of BP values can be stored. The cuff (for wrist circumference 13.5 cm–21.5 cm) can fully surround the wrist, which can capture the BP results more accurately.

Procedure

The validation process was performed by two observers with an independent supervisor experienced in BP measurement and retrained on mercury BP measurement according to the Universal Standard (ISO 81060-2:2018/AMD 1:2020).

Two connected (Y-tube) standard mercury sphygmomanometers (Jiangsu Yuyue Medical Equipment Co., Ltd., China), which have been calibrated before the study initiation were used for reference auscultatory BP measurements. The cuff for an arm circumference of 22–40 cm was used in the validation study.

All subjects were measured with the left upper arm and left wrist. During validation, participants were comfortably seated with the legs uncrossed and feet flat on the floor, the arm and wrist were kept at the heart level with the back, elbow, and forearm supported, and before the first reading was taken a period of at least 5 min was allowed to elapse. The same arm sequential method was applied with two entry BP measurements followed by four reference measurements taken alternately with three test device measurements. The two observers were blinded to each other’s readings and the test device results. The supervisor recorded the test device measurements and checked the observers’ measurements. In the case of disagreement between the observers, additional pairs of measurements were performed. A maximum of eight pairs of BP determinations were allowed after which the subject was excluded.

Analysis

Data were analyzed according to Criteria 1 and 2 in the Universal Standard (ISO 81060-2:2018/AMD 1:2020). Bland–Altman plots were also used to assess the agreement between the test device and the reference device.

Results

Ninety individuals were recruited and 270 pairs of BP comparisons were analyzed. The 90 participants included 47 (52.22%) men and 43 (47.78%) women with a mean age of 45.13 ± 14.95 years (range: 18–89 years) and a mean wrist circumference of 17.38 ± 2.20 cm (range:13.5–21.5 cm). The distribution of wrist circumference and other subject’s characteristics are presented in Table 1. The distribution of the reference BP measurement is presented in Table 2. The Universal Standard requirements for gender, age, BP and cuff distribution were fulfilled.

Table 1.

Characteristics of the study participants (n = 90)

Age, y (range)	45.13 ± 14.95 y (18–89)
Men: women, n (%)	47:43 (52.22:47.78)
Wrist circumstance, cm (range)	17.38 ± 2.20 (13.5–21.5)
Percentage of the participants with 13.5–15.5 cm, %	26.67
Percentage of the participants with 15.5–17.50 cm, %	28.89
Percentage of the participants with 17.5–19.5 cm, %	32.22
Percentage of the participants with 19.5–21.5 cm, %	26.67
Percentage of the participants with 20.5–21.5 cm, %	11.11
Percentage of the participants with 13.5–14.5 cm, %	14.44

Data are expressed as the means ± SD or percentages or number.

Table 2.

Distribution of reference blood pressure measurements

SBP	≤100 mmHg	≥160 mmHg	≥140 mmHg
	21.67%	9.72%	25.28%
DBP	≤60 mmHg	≥100 mmHg	≥85 mmHg
	7.78%	8.33%	26.11%

The validation analysis is shown in Table 3. According to Criterion 1, the mean difference of SBP between the test device and the reference device was 1.51 mmHg, with an SD of 6.48 mmHg. The mean difference of DBP was −0.44 mmHg, with an SD of 5.98 mmHg.The mean difference between SBP and DBP was less than 5 mm Hg, and the SD was less than 8 mmHg. According to Criterion 2, the mean difference of SBP between the test device and the reference device was 1.51 mmHg, and the SD was 5.88 mmHg, which was less than 6.78 mmHg. The mean difference of DBP was −0.44 mmHg, and the SD was 5.22 mmHg, which was less than 6.93 mmHg. The cuff and device pass for wrist measurement. Standardized Bland–Altman scatter plots of the test-reference BP differences against their average are shown in Figs. 1 and 2.

Table 3.

Validation study results

	Pass requirement	Achieved
		SBP	DBP
Criterion 1 (270 BP pairs)
Mean BP difference (mmHg)	≤5	1.51	−0.44
SD (mmHg)	≤8	6.48	5.98
		Pass	Pass
Criterion 2 (90 subjects)
SD (mmHg, SBP/DBP)	≤6.78/6.93	5.88	5.22
		Pass	Pass
Result		Pass

Fig. 1.

Bland–Altman scatter plots of systolic differences between the test device and reference, and the mean pressure of device and reference values for the U60EH Wrist Electronic Blood Pressure Monitor.

Fig. 2.

Bland–Altman scatter plots of diastolic blood pressure differences between the test device and reference, and the mean pressure of device and reference values for the U60EH Wrist Electronic Blood Pressure Monitor.

Discussion

In practice, BP measurements of wrist devices are influenced by several factors such as the position of the wrist relative to the heart and cuff size [3,4]. Correctly wrapping the cuff around the wrist and keeping the device at the level of the heart during BP measurement is importance to an accurate reading [5]. Generally speaking, old people might have difficulty following recommendations to maintain a steady arm position necessary for the measurements. In order to make the directions much easier to be understood, simple statements and clear diagrams were used in the product specification. In terms of operation process design, it adopts a simple and convenient way to wear, and users can operate with one hand. The backlit display makes it easier to read. In a word, in both clinical practice and self-BP monitoring, the manufacturer’s operating instructions must be followed precisely to ensure accurate readings.

In particular, a future study evaluating the difference between BP measured by a wrist-type BP monitor and that measured by an upper-arm BP monitoring might be needed in order to assess the differences. As the participants of the validation study were recruited from a general adult population, the accuracy of the devices for special populations, such as in children, in pregnant patients, or in those patients whose wrist circumference is within the range of the cuff provided, but are on arms that are quite fat or thick, needs to be further investigated.

Conclusion

This is a typical application of the ISO Universal Standard (ISO 81060-2:2018/AMD 1:2020) for the validation of the U60EH wrist BP monitor in the general population. There were no issues with the device use during the study. The results showed that the U60EH Wrist Electronic Blood Pressure Monitor fulfills the accuracy criteria of the Universal Standard in the general population and can be recommended for home and clinical use.

Acknowledgements

The study was funded by Shenzhen Urion Technology Co., Ltd., Shenzhen, China.

Sicong Mu conceived the idea of the article. Min Zhu and Liping Ma provided important suggestions. Lixiu Fang wrote the initial draft of the article. All authors read and approved the final article.

Conflicts of interest

There are no conflicts of interest.