EVIDENCE FOR OZONE-INDUCED SMALL-AIRWAY DYSFUNCTION - LACK OF MENSTRUAL-CYCLE AND GENDER EFFECTS

Recently, we analyzed FEF(25-75) isovolumetrically to assess the acute effects of ozone (O-3) on small-airway function: the reduction in iso volumetric (isoV) FEF(25-75) at end exposure progressed during the nex t 25 min even as FVC was recovering. To evaluate this effect over a lo nger period, we measured isovolumetric FEFs, helium-oxygen (He-O-2) vo lume of isoflow (V-isoV), the multiple breath nitrogen washout (MBNW) curve, FRC, and RV in 24 subjects 24 h after a 130-min exposure to fil tered air (FA) and O-3 (0.35 ppm). Men and women were studied to test for gender-based differences in response, after first determining that menstrual-cycle phase did not itself influence response. Isovolumetri c FEF(25-75), V-max50, and V-max75 were reduced about equally at 25 mi n after O-3 exposure (p less than or equal to 0.02) and showed no reco very at 24 h. FVC and FEV(1), although still depressed after 24 h (p < 0.05), showed substantial recovery (p < 0.01). FRC, RV, and V-isoV sh owed no effect of O-3 exposure. No gender differences in O-3 responsiv eness were found. In summary, O-3-induced reductions in isovolumetric flow rates, suggestive of small-airway dysfunction, may persist for 24 h following acute exposure to O-3, a timecourse consistent with infla mmation.