Introduction
Currently, the worldwide Standard for validation of automated sphygmomanometers is ISO 81060-2, 2018 [1]. Clinically it is critical that devices estimate blood pressure (BP) accurately for optimal diagnosis and treatment of numerous conditions, especially hypertension. Out-of-office BP readings have become more accepted, as they have been shown to be of great value [2]. To address this evolving clinical trend, A&D Medical has developed and tested the UM-212BLE in adults and children.
Methods
Testing was performed at Clinimark LLC in Louisville, Colorado, USA. Subjects were recruited from the general population; many had been tested before in previous validation studies. Their BPs have been noted to be consistent and often in BP ‘bins’ required by the Standard, which can be somewhat difficult to fill. The subjects were categorized as required for BP, gender, age, and arm circumference. Subjects with detected cardiac arrhythmias were excluded, as were subjects whose other criteria values were outside of the desired ranges [1].
The UM-212BLE is a battery-operated oscillometric device that has a feature that allows the clinician to listen to K-sounds during cuff deflation. The inflation pressure and deflation speed are adjustable (variable inflation). There are also settings for the estimation of automated office BP [2]. The device has Bluetooth as a standard feature.
Five BP cuffs were tested with arm circumference ranges from 12 to 17 cm, 16 to 24 cm, 22 to 32 cm, 31 to 45 cm, and 41 to 50 cm. The reference auscultatory cuff was of a two-piece construction. The cuff selected for reference measurements fulfilled the bladder width-to-arm circumference ratio of 0.37–0.50 [2].
The protocol followed was that described in the Standard [1]. In brief, the subjects were seated in a quiet room for 5 min with feet flat on the floor, back supported, and the arm with the cuff supported at the level of the heart. No talking was allowed. The procedure used was the same-arm sequential comparing bracketed auscultatory values by two observers blinded both to each other and the device values. There was a 60-s interval between sequential BP estimates. Korotkoff (K) 1 and K5 (last K sound audible) sounds were used to determine auscultatory SBP and DBP, respectively.
The data reported followed the Standard requirements [1], that is, the mean and SD of the device values minus auscultatory values. Results of Criteria 1 and 2 analyses are reported (Tables 1 and 2). Bland–Altman and Alpert [3] plots were constructed for clinical examination (Fig. 1a–d).
Table 1 -
Blood pressure values and differences: distribution of auscultatory reference blood pressure estimates [
n (%)]
| SBP (mmHg) |
DBP (mmHg) |
| ≤100 |
103 (40.4) |
≤60 |
33 (12.9) |
| ≥140 |
53 (20.8) |
≥85 |
74 (29.0) |
| ≥160 |
13 (5.1) |
≥100 |
15 (5.9) |
Table 2 -
Blood pressure values and differences: device minus reference blood pressures
|
Criterion 1 |
Criterion 2 |
| Mean |
SD |
SD permitted |
SD achieved |
| SBP |
3.94 |
6.89 |
5.70 |
5.56 |
| DBP |
2.09 |
6.68 |
6.62 |
6.01 |
| Allowed |
5.0 |
8.0 |
|
|
;)
Fig. 1: (a) Bland–Altman plot of SBP; (b) Bland–Altman plot of DBP; (c) Alpert plot of SBP error by limb circumference; (d) Alpert plot of DBP error by limb circumference; SS, extra small; SA, small adult; A, adult; LA, large adult; LL, extra large.
Results
A total of 101 subjects were recruited. Sixteen were not included because of BP variability, arrhythmia, or failure to cooperate. The final study group consisted of 85 subjects (44 females and 41 males) ranging in age from 3 to 80 years old. There were 35 children (ages 3–12) and 50 adults (ages 13–80).
Tables 1 and 2 demonstrate the BP values achieved; all values met or exceeded the Standard requirements. In addition, this table shows the required Criterion 1 and Criterion 2 statistical results. All achieved values passed the Standard requirements. Tables 3 and 4 show the data for the cuff and limb size requirements analyses.
Table 3 -
Limb size distribution
| Distribution of test participants’ limb circumference in the full cuff size range (12–50 cm) of the test device |
|
Lower octile 12–16.75 cm |
First quartile 12–21.5 cm |
Second quartile 21.5–31 cm |
Third quartile 41.5–55.75 cm |
Fourth quartile 55.75–70 cm |
Upper octile 62.875–70 cm |
| ISO required percentage |
10% |
20% |
20% |
20% |
20% |
10% |
| % of Participants (of 85) |
11% |
31% |
28% |
21% |
20% |
11% |
| # of Participants |
9 |
26 |
24 |
18 |
17 |
9 |
| Meets bin requirement |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Table 4 -
Cuff distribution
| Distribution of test participant arm circumference in the specified cuff size range of the test device |
| Cuff |
Specified range (cm) |
Minimum required # of participants (of 85 participants) |
Number of test participants |
Meets requirement |
| SS |
12–17 |
6 |
13 |
Yes |
| SA |
16–24 |
9 |
24 |
Yes |
| A |
22–32 |
11 |
16 |
Yes |
| LA |
31–45 |
16 |
18 |
Yes |
| LL |
41–50 |
10 |
14 |
Yes |
A, adult; SS, extra small; SA, small adult; LA, large adult; LL, extra large.
Figure 1a and b shows the Bland–Altman plots for both SBP and DBP. There does not appear to be any systematic trend for inaccuracy across the BP ranges studied. In addition, the newly required plots of device minus reference values on the y-axis and arm circumference on the x-axis (Alpert plot; [3]) for both SBP and DBP are shown in Fig. 1c and d. There does not appear to be any systematic trend for inaccuracy from the smallest to largest arm circumference for either SBP or DBP.
Discussion
The A&D UM-212BLE passed all of the requirements in the worldwide ISO 81060-2, 2018, Standard. The features that make this device clinically superior include automated office BP, variable inflation, dual measurement (oscillometry, auscultation) modes, a wide range of tested cuffs, and full validation in the pediatric population. As out-of-office BP measurement becomes more critical, having variable programmable automated office BP is desirable. The ability to control both the height of inflation and the speed of deflation will improve subject/patient comfort. If the clinician has concerns about the automated oscillometric readings, he/she can switch to the auscultatory mode and listen to K sounds for confirmation. A wide range of cuff sizes, from 12 to 50 cm, is needed for clinical care of children up to and including large/obese arms. Large arm sizes have become more prevalent in the worldwide population [2]. There are relatively few devices currently available that have been validated in children: the UM-212BLE fills that gap. Another ‘added feature’ is automated arrhythmia detection to alert the clinician to the possibility of issues with accurate BP estimation.
Acknowledgements
The author thanks Andrea Patters for her editorial assistance.
Conflicts of interest
There are no conflicts of interest.
References
1. International Organization for Standards. ISO 81060-2, 2018, Amendment 1, 2020. Non-invasive sphygmomanometers: Part 2: Clinical investigation of intermittent automated measurement type. 2018.
https://www.iso/org/standard/73333.html. [Accessed 10 October 2022].
2. Muntner P, Shimbo D, Carey RM, Charleston JB, Gaillard T, Misra S, et al. Measurement of blood pressure in humans. A scientific statement from the American Heart Association. Hypertension 2019; 73:e35–e36.
3. Alpert BS, Sarkis J, Dart RA, Quinn D. Addressing the wide-range cuff dilemma. Blood Press Monit 2020; 25:58–59.
