Am. J. Respir. Crit. Care Med., Vol 152, No. 3, Sep 1995, 988-996.
Evidence for ozone-induced small-airway dysfunction: lack of menstrual- cycle and gender effects
GG Weinmann, M Weidenbach-Gerbase, WM Foster, H Zacur and R Frank
Department of Environmental Health Sciences, Johns Hopkins School of Hygiene and Public Health, Baltimore, Maryland, USA.
Recently, we analyzed FEF25-75 isovolumetrically to assess the acute
effects of ozone (O3) on small-airway function: the reduction in
isovolumetric (isoV) FEF25-75 at end exposure progressed during the next 25
min even as FVC was recovering. To evaluate this effect over a longer
period, we measured isovolumetric FEFs, helium-oxygen (He-O2) volume of
isoflow (VisoV), the multiple breath nitrogen washout (MBNW) curve, FRC,
and RV in 24 subjects 24 h after a 130-min exposure to filtered air (FA)
and O3 (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. Isovolumetric FEF25-75, Vmax50, and
Vmax75 were reduced about equally at 25 min after O3 exposure (p < or =
0.02) and showed no recovery at 24 h. FVC and FEV1, although still
depressed after 24 h (p < 0.05), showed substantial recovery (p <
0.01). FRC, RV, and VisoV showed no effect of O3 exposure. No gender
differences in O3 responsiveness were found. In summary, O3-induced
reductions in isovolumetric flow rates, suggestive of small-airway
dysfunction, may persist for 24 h following acute exposure to O3, a
time-course consistent with inflammation.
