The 2017 US Clinical Guidelines for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults 1 stressed the need for devices to be ‘validated with an internationally accepted protocol’ and that the results be ‘published in a peer-reviewed journal’ (p. 29). This mandate is equally necessary for devices used in hospitals, clinics, and self-measurement sites, such as patients’ homes. Devices that utilize inflation-based algorithms take much less time for each blood pressure (BP) determination, with less discomfort. The Welch Allyn Pro BP 2000 is a professional-grade automated sphygmomanometer that uses inflation-based readings with deflation ‘back-up’ and has the added feature of arrhythmia detection. Blood pressure values measured in the presence of arrhythmia are likely to be inaccurate and, thus, should be reported to a patient’s healthcare provider for clinical acceptance 2.
This study reports the results of independent validation testing in a combined pediatric and adult population.
Patients and methods
The study was carried out at Clinimark, a clinical research center in Louisville, Colorado. Clinimark investigators and staff have performed many such validation studies using the ANSI/AAMI/ISO protocol. The protocol was approved by the Salus Independent Review Board before clinical testing. All patients provided written consent, or assent, depending on age. Ninety patients who fulfilled the sex (≤30% male) and age requirements were consented, but two were eliminated: one because the systolic BP variation was more than 12 mmHg and one because of poorly audible Korotkoff sounds. Thus, a total of 88 (53 adults/adolescents older than 12 years of age and 35 children 3–12 years old; 44% male, 56% female) participants comprised the final group reported here. Reference blood pressure distribution requirements and the data for each are given in Table 1.
The ANSI/AAMI/ISO protocol utilized was for the same-arm sequential data collection. The initial inflation/deflation cycle used manual auscultatory determination of the BP and the second cycle was performed by the Pro BP 2000 (Welch Allyn, Skaneateles Falls, New York, USA). The data from these two cycles were discarded. Manual auscultation was used for cycles 3, 5, 7, and 9. The device estimated BP on cycles 4, 6, and 8. The auscultatory values from the two blinded observers were averaged for cycles 3 and 5, and this value was compared with the device reading number 4. The same bracketing was used for the next sets of cycles; thus, a total of three comparisons of auscultatory to device BPs were recorded. The statistical analyses prescribed in the Standard 2 were carried out.
The Standard 2 calls for the use of K5 as the surrogate for diastolic BP in adults and K4 in children. These recommendations for children are based on the only known published data comparing direct intra-arterial BP with that obtained by auscultation (references 26 and 27 in the Standard).
Because of the wide range of arm circumferences, seven cuffs were used for the device readings. The characteristics and distribution of the individual cuffs are shown in Table 2. The two long cuffs were produced and tested for patients whose upper arms were high in circumference, but short in length. The long cuff was utilized when the next size larger cuff would have extended over the elbow joint.
All of the Standard requirements for sex, age, BP values, and number of each size cuff used were fulfilled. The Standard requires that two different BP differences (device minus auscultation) be met. Using all 264 comparisons (criterion 1) and 88 comparisons (three comparisons per patient averaged before analysis – criterion 2), the mean±SD of the device to manual BP differences were calculated and are shown in Table 3.
Bland–Altman plots were drawn to show the distribution of the data points across the BP ranges (Fig. 1a and b). Of the 35 children, K4 was audible and utilized in 34; K5 was used in the other child.
The Pro BP 2000 fulfilled all criteria of the current ANSI/AAMI/ISO Standard 2. The means and SDs were well within the acceptable ranges. The algorithm is inflation based, making the inflation/deflation cycle about 20 s in duration. This also restricts the ‘overshoot’ necessary for deflation-based devices. The comfort level for the patient is superior for the Pro BP 2000 compared with deflation-based devices.
The software has arrhythmia detection. If the R–R intervals (impulses) vary more than 20%, a warning alarm is triggered to alert the patient, nurse, physician, etc., that the BP value displayed may not be accurate. The cycle should be repeated in an attempt to obtain a value that can be used for clinical assessment.
The algorithm within the Pro BP 2000 is the same as in many other Welch Allyn professional-grade hospital and office devices. That implies that the healthcare professional can use the Pro BP 2000 BP data similar to those obtained in traditional office settings. The Pro BP 2000 can be used in professional applications at a low cost. For the self-measurement application, Welch Allyn manufactures the Home BP 1700 (Welch Allyn), which uses the same algorithm as the Pro BP 2000, giving the healthcare professional confidence in the BP values obtained with that device.
The Flexi Port (Welch Allyn) reusable cuff family has been used successfully with numerous automated sphygmomanometers. The availability of a long cuff in two sizes may be commonly needed in our current overweight and obese population.
The study of the Pro BP 2000 was carried out with funding from Welch Allyn.
The author thanks Andrea Patters for her editorial expertise.
Conflicts of interest
Bruce S. Alpert serves as a consultant to Welch Allyn.
1. Whelton PK, Carey RM, Aronow WS, Casey DE Jr, Collins KJ, Dennison Himmelfarb C, et al. ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults
: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Hypertension 2018; 17:1269–1324.
2. Association for the advancement of medical instrumentation. Non-invasive sphygmomanometers – part 2: clinical investigation of automated measurement type ANSI/AAMI/ISO 81060-2/ANSI-AAMI, 2nd ed. Arlington, VA: AAMI 2013. Available at: http://my.aami.org/store/detail.aspx?id=8106002