A Respiratory Ozone Analyzer Optimized for High Resolution and Swift Dynamic Response During Exercise Conditions

ABSTRACT

The breath-to-breath determination of total respiratory ozone (O₃) uptake requires the monitoring of O₃ concentration at the airway opening with an instrument that responds rapidly relative to the frequency of respiration. Originally, the authors developed an analyzer that used the homogeneous chemiluminescent reaction of O₃ with 2-methyl-2-butene, but it was suitable only for monitoring O₃ during quiet breathing and light exercise (Ben-Jebria and Ultman, Rev Sci Instrum 1989; 60:3004–11, and Ben-Jebria et al., Rev Sci Instrum 1990; 61:3435–39). The improvement of performance characteristics of the aforementioned analyzer enabled the authors to use the newly constructed and self-contained instrument, which used ethylene as the reactant gas, for respiratory O₃ monitoring during moderate-to-heavy exercise. Operating at a reaction chamber pressure of 350 torr, an ethylene/sample flow ratio of 4:1, and a sampling flow of 0.6 Ipm, the authors achieved an optimum analyzer performance (i.e., 10–90% step–response of 70 msec and a minimum resolution of 0.006 ppm O₃). Furthermore, the new instrument did not exhibit the nonlinear calibration and the CO₂ interference suffered by the original analyzer. To demonstrate the quality of the new O₃ analyzer in a respiratory application (i.e., total O₃ uptake), the authors measured a series of single breaths on two subjects who breathed 0.11 and 0.43 ppm O₃-in-air mixtures for 15 min during rest, and during moderate and heavy exercise.