(334d) The Development of a New Differential Pressure Flow Meter for Bidirectional Measurement of Human Breath Flow

We have developed and verified the performance of a new differential pressure flow meter, the Confined Pitot Tube, for the purpose of measuring breathing gas-flow. The sensor provides a simple, highly sensitive, low-resistance flow measurement tool, applicable to measuring both exhalation and inhalation flows. The sensor consists of an elliptical pitot tube which causes a large obstruction in flow inside of a pipe, where the pipe also provides an expansion around the pitot tube. By designing the flow meter in such a way, it has the benefit of measuring the stagnant pressure due to the velocity of the fluid (like a standard Pitot Tube), as well as measuring the pressure buildup due to the viscous and inertial effects of forcing the fluid around the pitot tube while confined. Since there are additional effects from confinement, the flow meter is also equipped to measure inhalation flows with the same pressure sensing element. With the Confined Pitot Tube flow meter, we can measure low flows with usable sensitivity (>2Pa at 2L/min), while attaining low flow-resistance at higher flows (>115Pa at 20L/min). In order to characterize flow properties of the system, Comsol Multiphysics was employed to simulate pressure values in laminar and turbulent cases and characterize the system.