Analytical Chemistry
Analytical Chemistry
5 years ago

Inline Shunt Flow Monitor for Hydrocephalus

Inline Shunt Flow Monitor for Hydrocephalus
Purnendu K. Dasgupta, Brian Stamos, Chuchu Qin
In hydrocephalus, cerebrospinal fluid (CSF) builds up in the cranial cavity causing swelling of the head and potentially brain damage. A shunt to drain the fluid into a body cavity is now universally used, but failure is all too common. Techniques for ascertaining shunt failure are time-consuming, expertise-dependent, and often inconclusive. We report here an inline system that reliably and quantitatively measures the CSF flow rate. The system uses a single thermistor to both heat the surrounding and to sense the temperature. In the heating mode, the thermistor is subjected to a 5 s voltage pulse. In the sensing mode, it is part of a Wheatstone’s bridge, the output being proportional to temperature. The signal, Vi – Vf, which is the net change ΔV in the bridge output immediately before and after the heat pulse, depends both on the flow rate and the surrounding temperature. In vitro, a single equation, flow rate = 3.75 × 10–6 × ΔV(−9.568+1.088 Vi) provided good prediction for the flow rate, with 6.3% RMS relative error. The sensor behavior is reported for flow rates between 0–52.5 mL/h at 32–39 °C, adequately covering the range of interest.

Publisher URL: http://dx.doi.org/10.1021/acs.analchem.7b02034

DOI: 10.1021/acs.analchem.7b02034

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