Development of an Upper Arm Phantom for BP Measurement
Cardiovascular diseases, such as hypertension, is one of the most commonly occurring afflictions throughout the world. Blood pressure (BP) measurement is critical in the diagnostic analysis of cardiovascular health. The cuff-based non-invasive blood pressure (NIBP) measurement devices are marked by inaccuracies in the estimation of BP, attributing to assumptions related to upper arm’s geometry, soft tissue mechanical properties, and distribution of uniform cuff pressure (CP).
The research aims to develop upper arm numerical models and a physical phantom to investigate the displacements, stresses, volume changes on the upper arm soft tissue during NIBP measurement. The characterisation of these quantities aids in understanding the cause of BP estimation errors in NIBP measurement devices. Annular concentric finite element (FE) models were developed and verified using the principles of continuum mechanics.
An upper arm model of anatomically accurate geometry was developed. A range of silicone materials was characterised for their mechanical properties to formulate a hyperelastic constitutive model for Finite Element Analysis (FEA) of the upper arm BP simulation. The characterisation aided in selecting the appropriate material to fabricate the anatomical upper arm phantom. A test rig was built for the arm phantom to obtain pressure-volume relationship of the soft tissue components during NIBP measurement. The anatomically accurate FE model was validated with the upper arm phantom for the pressure-volume relationship. The displacement, strain effects of the tissue contact conditions on the soft tissue during NIBP were analysed. It was concluded that the tissue mechanical properties, geometry, and tissue contact conditions of the upper arm plays a crucial role in estimation of BP using NIBP measurement devices.