Measuring blood pressure from Korotkoff sounds as the brachial cuff inflates on average provides higher values than when the cuff deflates

Objectives. In this study, we test the hypothesis that if, as demonstrated in a previous study, brachial arteries exhibit hysteresis as the occluding cuff is deflated and fail to open until cuff pressure (CP) is well below true intra-arterial blood pressure (IAPB), estimating systolic (SBP) and diastolic blood pressure (DBP) from the presence of Korotkoff sounds (KS) as CP increases may eliminate these errors and give more accurate estimates of SBP and DBP relative to IABP readings. Approach. In 62 subjects of varying ages (45.1 +/- 19.8, range 20.6-75.8 years), including 44 men (45.3 +/- 19.4, range 20.6-75.8 years) and 18 women (44.4 +/- 21.4, range 20.9-75.3 years), we sequentially recorded SBP and DBP both during cuff inflation and cuff deflation using KS. Results. There was a significant (p < 0.0001) increase in SBP from 122.8 +/- 13.2 to 127.6 +/- 13.0 mmHg and a significant (p = 0.0001) increase in DBP from 70.0 +/- 9.0 to 77.5 +/- 9.7 mmHg. Of the 62 subjects, 51 showed a positive increase in SBP (0-14 mmHg) and 11 subjects showed a reduction (-0.3 to -7 mmHg). The average differences for SBP and DBP estimates derived as the cuff inflates and those derived as the cuff deflates were 4.8 +/- 4.6 mmHg and 2.5 +/- 4.6 mmHg, not dissimilar to the differences reported between IABP and non-invasive blood pressure measurements. Although we could not develop multiparameter linear or non-linear models to explain this phenomenon we have clearly demonstrated through ANOVA tests that both body mass index (BMI) and pulse wave velocity are implicated, supporting the hypothesis that the phenomenon is associated with age, higher BMI and stiffer arteries. Significance. The implications of this study are that brachial sphygmomanometry carried out during cuff inflation could be more accurate than measurements carried out as the cuff deflates. Further research is required to validate these results with IAPB measurements.