Absorbance or fluorescent sensors are used with which of the following?

a. Capnography c. In vitro blood gas analysis
b. Photoplethysmog-raphy d. In vivo blood gas analysis

ANS: D
In vivo blood gas monitors use optical sensors that are generally categorized in terms of how they modify the initial optical signal; they are classified as either absorbance or fluorescent sensors. Absorbance sensors absorb a fraction of the incident light as it is transmitted down the fiber and through the microcuvette. The amount of light transmitted is proportional to the concentration of the analyte in question. Fluorescent sensors use dyes that fluoresce when they are struck by light in the UV or near-UV visible range. Light from the monitor is transmitted to the microcuvette containing the dye. The concentration of the analyte in question can be measured by determining the ratio of fluorescent light emitted to the original excitation light signal.