Oscillometric Waveform Difference between Cuff Inflation and Deflation during Blood Pressure Measurement

The majority of automatic blood pressure (BP) measurement devices use the oscillometric method made during cuff inflation or deflation. However, there is currently little information available on the comparison of oscillometric waveform shape between cuff inflation and deflation. This study aimed to provide this information. Oscillometric cuff pressure waveforms were recorded digitally from 10 normotensive subjects during standard BP measurement at slow linear inflation and deflation rates of 2-3 mmHg/s. Three repeat sessions were performed for each subject. Four features were quantified for each oscillometric waveform: the maximum oscillometric pulse peak amplitude (Amax) and three cuff pressure widths corresponding to 70%, 50% and 30% of Amax (denoted as W70, W50 and W30 respectively). For all subjects, these oscillometric waveform features were then compared between cuff inflation and deflation. Analysis of variance showed that there was no significant difference between the three repeat measurements for all four waveform features (all P>0.4). Mean Amax from cuff inflation was 0.7 mmHg higher (mean +/- SD: 3.7 +/- 0.9 vs. 3.0 +/- 0.8 mmHg, P<0.001) than that from cuff deflation. For the cuff pressure widths at the three thresholds, W70 was not significantly different between cuff inflation and deflation, but W50 and W30 were both significantly narrower for cuff inflation by 12 mmHg (45 +/- 9 vs. 57 +/- 11 mmHg) and 22 mmHg narrower (67 +/- 10 vs. 89 +/- 12 mmHg) respectively; both P<0.001. The oscillometric waveform differences during BP measurement suggest that arteries may behave differently during cuff inflation and deflation.