NORMAL VARIATIONS IN SPIROMETRY IN HEALTH FOLLOWING PLACEBO INHALATION

Normal i.e., chance variations in spirometry were evaluated in 80 heal thy Indian adults by the measurement of base-line spirometric indices (FVC, FEV(1) and FEF(25-75%)) and the per cent changes following place bo administration of aerosolized saline. There was a mean per cent cha nge of 0.7, 0.4 and 0.3 per cent over the base-line values in FVC, FEV (1) and FEF(25-75%) respectively following placebo inhalation. The cut off responses for 95 per cent confidence limits were 11.2 per cent fo r FVC and 12.7 per cent for FEV, following placebo inhalation. Since t he test sample represents a healthy Indian population, a per cent chan ge greater than 12,7 per cent in FEV, is more than that observed in 95 per cent of healthy Indians. It is suggested that for both Delta FEV( 1), per cent and Delta FVC per tent, the lower limit should be fixed a t more than 15 per cent to define 'abnormality' in clinical practice.