Solution Idea: Introducing the Bramwell-Hill Principle

After much discussion and evaluation of various methods to monitor cardiac output (CO), our team has concluded that the solution with the most potential is one based on the Bramwell-Hill Principle.

Based on the problem landscape and the gaps associated with current solutions on the market, we decided that our solution must meet two main design criteria to be viable in the hemodynamic market: noninvasiveness and accuracy in measuring CO trends. Of these criteria, invasiveness is critical to consider since the primary problem with CO monitoring stems from the high risk and invasiveness associated with the current standard of care. The current solution landscape reflects stakeholders’ needs for a less invasive device. However, there exist gaps in the landscape in terms of measuring CO trends accurately in critically ill patients in ICUs, since these devices rely largely on static vascular compliance and resistance which realistically change in these patients.

Our solution concept will indirectly measure CO using the Bramwell-Hill Equation, which relates pulse wave velocity to stroke volume. Our solution is based on an established scientific principle that has shown strong correlation in calculating CO, even in changing cardiovasculature. The process for deriving CO follows from the formula: SV = (AVTV*PP)/(q*(PWV^2)) where SV is stroke volume, AVTV is arterial vascular tree volume, PP is pulse pressure, q is blood density, and PWV is aortic pulse wave velocity. CO can be calculated using CO = SV ∗ HR, where HR is heart rate. As seen in the figure below, our proposed solution will noninvasively obtain measurements for each component of the Bramwell-Hill equation.

Supporting Literature:

C. Babbs, 'Noninvasive measurement of cardiac stroke volume using pulse wave velocity and aortic dimensions: a simulation study', BioMedical Engineering OnLine, vol. 13, no. 1, p. 137, 2014.