BRONCHOSCOPIC DETERMINATION OF OZONE UPTAKE IN HUMANS

Measurements of ozone uptake efficiency in the human respiratory tract provide critical information toward understanding ozone dose-response characteristics. We measured ozone uptake efficiency by different regions of the respiratory tract between the mouth and bronchus intermedius in 10 healthy, resting, nonsmoking male and female subjects. The distal end of a bronchoscope was sequentially positioned at the bronchus intermedius (BI), main carina (CAR), upper trachea, and above the vocal cords. Ozone concentration was measured continuously at each sight using a rapid-responding ozone analyzer. During sampling subjects breathed through a mouthpiece connected to a pneumotachograph at a paced rate of 12 breaths/min. Integration of the product of the flow and ozone concentrations during inspiration and expiration provided the ozone mass passing each anatomic location during each phase of respiration. On inspiration the uptake efficiencies of ozone by structures between the mouth and each location j (E(m-j)) were 0.176 +/- 0.037 (SE), 0.271 +/- 0.024, 0.355 +/- 0.030, and 0.325 +/- 0.031 for above the vocal cords, upper trachea, CAR, and BI, respectively. A significant effect of location on E(m-j) was found by analysis of variance (P < 0.0002). Pairwise comparisons showed that E(m-j) increased as the lung penetration increased except between CAR and BI, which was not significantly different.