Study population
Normotensive or hypertensive (systolic BP ≥140 mm Hg, diastolic BP ≥90 mm Hg) male or female subjects (aged ≥18 years) were included. Exclusion criteria comprised previous experience with wrist BP measurement devices, wrist circumferences 19.5 cm, history of significant cardiac arrhythmia, hypertensive crisis, claudication or restricted blood flow, damage or injury of the left wrist, participation in any other clinical trial at the same time, pregnancy, and lactation. Approval was granted by an independent and applicable Ethics Review Committee and written, informed consent was obtained from each subject before entry into the study.
BP measurements
Arm circumferences were measured for both arms and wrists. The appropriate cuff size (for the auscultatory device) was selected for each subject. For the BP 2000 device, only one cuff size was available (wrist circumference, 13.5 to 19.5 cm).
Subjects were assigned randomly into two groups in a crossover study design, with a duration of 16 days. From days 1 to 8, group 1 was assigned home measurements with BP 2000 with the activated position sensor (BP 2000+P), and group 2 with BP 2000 without activated position sensor (BP 2000−P). A 24-h BP measurement device was used to record BP in all subjects between days 8 and 9. From days 9 to 16, group 1 was provided with BP 2000−P, and group 2 with BP 2000+P. A no responder test was performed on day 16. The mean value of three office measurements on the left arm was compared with the mean value of three supervised measurements with the activated position sensor (BP 2000+P).
The ABPM was performed with a highly accurate device (A&D TM-2430) validated according to the Association for the Advancement of Medical Instrumentation (AAMI) and British Hypertension Society protocols (grade A/A) and recommended for clinical use.1,2 The ABPM was performed during average working days and BP was measured at present 15-min intervals from 7 AM to 10 PM (daytime readings), and at 20-min intervals at night (nighttime readings). We used mean whole-day ABPM (24 h) and daytime readings for statistical comparisons with office readings and self-measured BP values.
Conventional sphygmomanometric office BP measurement was performed in the sitting position at 2-min intervals with an auscultatory BP measurement device according to the recommendations of the American Heart Association with at least four measurements/patient at the entry of the study. Two office measurements per arm were performed at study entry.
Home BP measurements were performed with the BP 2000, a new oscillometric wrist BP monitor (Braun GmbH, Kronberg, Germany). The cuff of the device was inflated and deflated automatically after the start of the measurement. Systolic and diastolic BP, heart rate, and the date and time of measurement were stored in the device memory automatically. All subjects were requested to measure BP at home according to the instructions for use and to measure their BP twice in the morning and twice in the evening. For statistical analysis only stored data were used.
Before the start of the study, all BP measurement systems were calibrated according to the manufacturers’ instructions. All measurements (ABPM, office, and self-measured readings) were performed at the left arm/wrist.
Before the study started, the investigators were trained for the appropriate use of any BP measurement device used in the study and had to demonstrate proficiency with all Blood Pressure Monitor according to the manufacturers’ instructions.