Automatic blood pressure monitors (oscillometers) with the cuff placed over the upper arm give different systolic BP (SBP) readings to the Korotkoff/Riva-Rocci auscultatory method, influenced by quantity of soft tissue and arm circumference. Other studies have examined whether SBP measurement at the wrist or forearm is more accurate, with limited success. No literature was found on oscillometer use at the elbow. We therefore examined whether oscillometric SBP at the elbow was more accurate than the upper arm and the influence of demographic and anthropometric variables, using simultaneous Doppler return-to-flow at the wrist as the comparative method for SBP. Triplicate SBP readings at the upper arm and elbow were recorded in 62 participants.
Bland-Altman plots showed similarly poor agreement between the oscillometers and Dopplers at each cuff position, despite upper arm oscillometry being a clinically validated method of blood pressure measurement. We found a significant difference (p < 0.01) between the mean oscillometer SBP readings at the upper arm and elbow, and between the mean Doppler SBP readings at the upper arm and elbow. On further analysis, we noticed that the difference between the oscillometric readings at the upper arm and elbow had an inverse relationship with both log transformation of triceps skinfold thickness (p = 0.013) and age (p = 0.014), although correlation between these two variables was not significant (p = 0.193), therefore avoiding collinearity. No relationship was found between the difference between Doppler readings and any anthropometric variables measured.
Placing the cuff over the elbow may therefore be a feasible alternative to a cuff over the upper arm, especially in those with a large quantity of non-muscular soft tissue and older people. Additional development of this method and further comparison is needed as we must adapt to the increasingly obese and elderly population.
- Blood pressure
- Automatic blood pressure machines
- Elbow cuff placement