Differences between brachial oscillometric arterial blood pressure measured during cuff inflation and cuff deflation

Objective: Brachial oscillometric arterial blood pressure (BP) assessment offers greater convenience and less user dependence compared to auscultatory and invasive BP assessment. More recent devices have adopted the method of estimating BP using the oscillometric waveform obtained during inflation of the pneumatic cuff rather than during deflation. At present there is a lack in awareness and understanding of differences between these two methods in the context of oscillometric BP estimation. This study aims to determine if there are differences in the arterial brachial BP measurements obtained during cuff inflation compared to cuff deflation.
Design and method: Brachial oscillometric BP was measured at baseline using two separate devices in triplicate in a randomised order in seated participants (n=27, 42±17 years, 12 female). One device estimated BP during cuff inflation whilst the other device estimated BP during cuff deflation. Differences were expressed as mean±standard deviation and compared using Bland-Altman plots and linear regression analysis.
Results: The average difference between devices for systolic BP (SBP) was -1.1±6.4 mmHg and for diastolic BP (DBP) it was 0.8±3.8 mmHg. There were no significant within-device BP differences across all measurements (p>0.05). Despite no significant between-device differences observed in either SBP or DBP (p>0.05), there was a large proportion of differences greater than 5 mmHg (SBP: 51% and DBP: 30%), with some differences greater than 10 mmHg (SBP: 22% and DBP: 6%). Heart rate was a contributing factor to the variation in SBP differences (p=0.02).
Conclusions: There were no significant differences between oscillometric brachial BP measured during cuff inflation or cuff deflation. However, the large variations in the readings that can be caused by differences in heart rate have implications when oscillometric BP devices are used as a reference for BP measurements, such as in the context of cuffless BP estimation.