Validation of WatchBP Office Ankle-brachial Index (ABI) Function
Condition: Hypertension
MeSH terms: Hypertension
Study type: Observational

Summary: 
      Measurement of the ankle-brachial index (ABI) with the oscillometric device WatchBP Office
      will be assessed compared to the reference method (Doppler).

      Ninety three adult subjects assessed for hypertension, treated or untreated, with complete
      study data were included. Data on the presence of cardiovascular (CV) disease and classical
      CV risk factors were recorded.

      All the ABI measurements of each individual participant will be performed by the same
      observer in a randomized order (concerning Doppler and WatchBP)
    

Detailed description: 
      All study measurements were performed under standardized conditions in a quiet examination
      room with 10 min rest in the supine position before measurements. Ankle-brachial index (ABI)
      was measured manually by Doppler and automatically by the oscillometric device in randomized
      order by a single investigator. Manual Doppler ABI was measured according to the American
      Heart Association guidelines using a continuous wave Doppler device (Hadeco Bidop ES-100V3,
      Kawasaki, Japan) with a 8 MHz probe. Systolic blood pressure was defined with a standard
      mercury sphygmomanometer by the first Doppler flow signal while deflating the cuff from a
      suprasystolic level in brachial, dorsalis pedis and posterior tibial arteries. Systolic
      pressure was determined sequentially for brachial, dorsalis pedis and posterior tibial
      arteries for each side and ABI was calculated for each leg by dividing the highest ankle
      pressure to the highest arm pressure. Automated ABI measurement was performed using a
      validated oscillometric blood pressure monitor designed for professional use in the office
      (WatchBP Office device; Microlife, Widnau, Switzerland). This device allows automated
      simultaneous both arms or arm and leg blood pressure measurements and thereby the calculation
      of ABI. The ABI results are displayed on the device screen.

      The study protocol included three steps: (i) an introductory familiarization automated ABI
      measurement, (ii) three simultaneous oscillometric both arms blood pressure measurements; in
      case of a consistent inter-arm difference ≥12 mmHg, the arm with the higher blood pressure
      was selected for the subsequent oscillometric ABI measurements (otherwise the right arm was
      used) and (iii) Doppler and automated ABI measurement in randomized order; Doppler ABI was
      measured once, whereas automated ABI calculation included triplicate simultaneous arm-leg
      measurements performed for each side. The occurrence of five sequential oscillometric errors
      was defined as a failure of the oscillometric device to measure ABI.
    

Intervention name(s): Doppler Ankle-Brachial Index measurement; WatchBP Office Ankle-Brachial Index measurement.
Intervention type(s): Device; Device
Intervention description(s): Measurement of the Ankle-Brachial Index by Doppler.; Measurement of Ankle-Brachial Index by WatchBP Office device.
Observational model: Case-Only
Time perspective: Cross-Sectional
Sampling method: Probability Sample
Study population: 
        Subjects assessed for hypertension including those with other cardiovascular risk factors
      
Keywords: ankle brachial index; WatchBP Office; oscillometric measurement