Francis, DanielHodgkinson, JaneWalton, ChristopherSizer, JeremyBlack, PaulLivingstone, BethFowler, Dawn P.Patel, Mitesh K.Tatam, Ralph P.2017-06-222017-06-222017-02-17Daniel Francis, Jane Hodgkinson, Christopher Walton, Jeremy Sizer, Paul Black, Beth Livingstone, Dawn P. Fowler, Mitesh K. Patel and Ralph P. Tatam. Mid-IR spectroscopic instrumentation for point-of-care diagnosis using a hollow silica waveguide gas cell. Optical Diagnostics and Sensing XVII: Toward Point-of-Care Diagnostics. Photonics West, 27 January - 1 February 2017, San Francisco, CA, USA.0277-786Xhttp://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2605726https://dspace.lib.cranfield.ac.uk/handle/1826/12095Laser spectroscopy provides the basis of instrumentation developed for the diagnosis of infectious disease, via quantification of organic biomarkers that are produced by associated bacteria. The technology is centred on a multichannel pulsed quantum cascade laser system that allows multiple lasers with different wavelengths to be used simultaneously, each selected to monitor a different diagnostic biomarker. The instrument also utilizes a hollow silica waveguide (HSW) gas cell which has a very high ratio of interaction pathlength to internal volume. This allows sensitive detection of low volume gas species from small volume biological samples. The spectroscopic performance of a range of HSW gas cells with different lengths and bore diameters has been assessed using methane as a test gas and a best-case limit of detection of 0.26 ppm was determined. The response time of this cell was measured as a 1,000 sccm flow of methane passed through it and was found to be 0.75 s. These results are compared with those obtained using a multi-pass Herriot cell. A prototype instrument has been built and approved for clinical trials for detection of lung infection in acute-care patients via analysis of ventilator breath. Demonstration of the instrument for headspace gas analysis is made by monitoring the methane emission from bovine faeces. The manufacture of a hospital-ready device for monitoring biomarkers of infection in the exhaled breath of intensive care ventilator patients is also presented.en©2017 SPIE. Please refer to any applicable publisher terms of use.Mid-infraredspectroscopyquantum cascade laserhollow silica waveguidebiomarkervolatile organicdiagnosticsheadspacepoint-of-careConference paper