The design and development of a direct and continuous sensor for the measurement of inhaled nitric oxide concentrations

Parikh, Bhairavi Rajiv

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The design and development of a direct and continuous sensor for the measurement of inhaled nitric oxide concentrations

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Gaseous nitric oxide, in concentrations between 0 and 20 ppm, is currently being used to treat patients with post-surgical complications and respiratory disorders. Currently available instruments are expensive and have problems that limit their usefulness for this application. This thesis discusses the development of an inexpensive, direct and continuous sensor for the measurement of inhaled nitric oxide. The prototype sensor incorporates a 0.125 cm, gas permeable, flow-thru liquid cell into a probe that can be incorporated into a ventilator circuit. Sensor operation is based on the complexation reaction of NO with cytochrome-c (Fe III), a biologically derived heme. The complex is monitored spectrophotometrically in the visible region of the spectrum at 563 nm by an optical spectrograph card. LabVIEW is used for all hardware control, signal acquisition, data processing, display and storage. The sensor has a sensitivity of 2x10-4 Abs/ppm, where Abs denotes absorbance units, a minimum detectable limit of 1.5 ppm, resolution of 0.5 ppm, is stable over the course of 8 hours, has less than 1 ppm error and a response time of less than 2 minutes. All aspects of sensor design and development will be discussed.

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