COMPARISON BETWEEN PEAK EXPIRATORY FLOW AND EXPIRATORY VOLUME IN ONE SECOND (FEV(1)) DURING BRONCHOCONSTRICTION INDUCED BY DIFFERENT STIMULI

To evaluate the sensitivity of peak expiratory flow (PEF), obtained by portable peak flow meter, in detecting mild changes in airway caliber as assessed by forced expiratory volume in 1 sec (FEV(1)), we studied 184 subjects who underwent different bronchial challenge tests for su spected bronchial asthma. We measured FEV(1) and PEF during bronchocon striction induced by different stimuli: allergen, methacholine, toluen e disocyanate vapors, exercise, or distilled water inh alation; a tota l of 186 tests were examined. Before and at different times after chal lenge, FEV(1) was measured, and immediately after, PEF was obtained by Mini-Wright or Assess Peak Flow Meter; each time FEV(1) and PEF were taken as the best of three satisfactory tracings. She median FEV(1) ch ange from baseline value of all steps in the different challenge tests was 7.5% (range: 0-66%), The correlation coefficients between FEV(1) and PEF percent changes in different challenge tests were low (Spearma n's rho: 0.27-8.69), with high scattering of the data. The concordance between classes of percent changes in FEV(1) and PEF was also low (Co hen's weighted kappa: 0.28-0.42). In subjects with a FEV(1) fall > 15% after challenge, the median PEF change after bronchoconstriction was lower than the corresponding FEV(1) change [17% (0-52) vs. 27% (17-66) ]. When different cutoff limits of PEF percent change were considered, the sensitivity of PEF to detect a significant change in FEV(1) (15 o r 20% change) during bronchoconstriction was low; specificity was in g eneral higher than sensitivity, We conclude that PEF and FEV(1) change s are poorly related during mild bronchoconstriction induced by differ ent stimuli. The low sensitivity of PEF to detect mild changes in airw ay caliber may represent a limit in the use of PEF in the day-to-day m onitoring of asthma.