Integrated cavity output spectroscopy measurements of NO levels in breath with a pulsed room-temperature QCL

A cavity-enhanced spectrometer is developed for detection of exhaled nitric oxide in human breath. A thermoelectrically cooled, pulsed, quantum cascade laser, coupled to a high-finesse cavity, is used for trace-gas measurements. The trace-gas analyzer operates at 5.2 microns and utilizes integrated cavity output spectroscopy. Effective optical path lengths of 1.5 km are achieved in a 50-cm-length cell with a sample volume of 60 mL. The instrument is also capable of simultaneously measuring CO2 concentration in exhaled breath. Measurements were performed on human breath samples as well as simulated breath samples. Here we report a detection limit of < 1 ppbv in 4 s for NO in human breath samples.