Design and Characterization of an Adjustable Passive Flow Regulator and Application to External CSF Drainage

Abstract

Passive valves that deliver a constant flow rate regardless of inlet pressure changes have numerous applications in research, industry, and medical fields. The present article describes a passive spring valve that can be adjusted manually to deliver the required flow rate. The valve consists of a movable rod with an engraved microchannel. The fluidic resistance of the device varies together with the inlet pressure to regulate the flow rate. A prototype was made and characterized. Flow-rate adjustment up to +/−30% of the nominal flow rate was shown. A simple numerical model of the fluid flow through the device was made to adapt the design to external ventricular drainage of cerebrospinal fluid (CSF). Some insights about the implementation of this solution are also discussed.

Physical Properties of Helium and Application in Respiratory Care

“…It was shown that up to generation 10, for a Reynolds number of about 60 with air, significant inertial losses can be observed. This result, which suggests that helium also reduces flow resistance in the laminar regime, is consistent with theory and other research, particularly in the field of passive flow control for medical applications, where minor losses in the laminar regime must be taken into account to obtain the desired constant flow rate [50][51][52][53][54][55]. The importance of these inertial losses in respiratory mechanics has also been reported in other studies [56][57][58][59][60].…”