Noninvasive Determination of Respiratory Ozone Absorption: Development of a Fast-Responding Ozone Analyzer

摘要

An ozone analyzer and an ozone bolus generator were developed and tested for future use in noninvasive measurements of ozone absorption along the human respiratory tract using the bolus-response technique. The analyzer, based on the chemiluminescent reaction of ozone with 2-methyl-2-butene, is sufficiently rapid and sensitive to measure changes in ozone concentration during a four-second breathing period at quiet respiratory flowrates of 300 mL/sec in human subjects. Its performance characteristics include a 90 percent step-response time of 110 msec, a linear calibration from 0.03 to 10 ppm ozone, a signal-to-noise ratio of 30 at 0.5 ppm ozone, and a minimum detection limit of 0.017 ppm ozone. The ozone bolus generator can produce single boluses containing as little as 0.35 micro g ozone in a volume of 19 mL, with a peak ozone fraction of up to 4 ppm. The analyzer and bolus generator were tested in bolus-response experiments at steady air flowrates of 50 to 200 mL/sec in excised pig and sheep tracheas. Twenty-five to 50 percent of the ozone introduced into the trachea was absorbed. Analysis of the mathematical moments of the bolus input and response curves and comparison to predictions of a diffusion theory indicate that ozone absorption is limited by diffusion processes in the airway lumen. (Copyright (c) 1990 Health Effects Institute.)