Measurement of blood pressure using the auscultatory and oscillometric methods in the same cuff deflation: validation and field trial of the A&D TM2421 monitor

We have evaluated under laboratory validation conditions and in an extensiv e field trial the behaviour of an ambulatory monitoring device that is capa ble of recording both by the Korotkoff-sound and oscillometric methods in a single cuff deflation (TM2421: A&D Co, Tokyo, Japan), The effects of subje ct age and blood pressure (BP) level on the accuracy and field reliability of the two methods implemented in the device have been determined. In the v alidation phase, automatic BP measurements were compared with readings by t wo trained observers in 96 subjects, and the results compared with the AAMI criteria for automatic BP monitors. In the field trial phase, the performa nces of Korotkoff-sound and oscillometric methods over a 24-h period of amb ulatory BP monitoring were compared in 515 subjects, with analysis of the a greement between the two methods in patients where both provided satisfacto ry recordings. In the validation phase, the Korotkoff-sound method gave sat isfactory results for both systolic and diastolic BP, but the oscillometric technique narrowly failed to meet the AAMI criteria for the measurement of either systolic or diastolic BP. In the field trial, the K-sound method fa iled to record BP accurately in 12% of subjects whereas the oscillometric m ethod was successful in all of these. Where both methods provided technical ly adequate records, agreement between mean values for each method was clos e. In 18% of patients, the availability of the oscillometric measurement as a 'back-up' method for the K-sound method significantly improved the numbe r of available measurements in the monitoring period, which should result i n improved accuracy and reproducibility of the ambulatory mean values.