Quality Assurance of Spirometric Measurement: Intraindividual Variability in Maximal Expiratory Flow Volume Curves

Abstract

The variability of the parameters derived from forced expiratory spirograms should be taken into accunt as a part of quality assurance systems for spirometric measurements. In this study, intraindividual variability of forced vital capacity (FVC), forced expiratory volume in 1s (FEV1), FEV1/ FVC, and peak expiratory flow rate (PEFR) were determined every other day for 5 days, in 16 healthy adults 20 to 32 years of age. Our results reveal that all the effort- dependent tests such as FVC, FEV1 and FEV1/FVC showed little variability, except for PEFR. The mean coefficients of variation (CV) for FVC, FEV1 and FEV1/FVC were 4.1%, 3.8% and 2.5%, respectively. The greatest variability was seen with PEFR, which had a mean CV of 10.2%. In these subjects, the magnitude of variability during the study period ranged from 0.11 to 0.21 L for FVC, from 0.3 to 2. 7% for FEV1/FVC, and from 1.5 to 2.8 L/s for PEFR. It is suggested that there are considerable intraindividual variability in parameters derived from the maximal expiratory flow volume curve. Quality assurance of spirometry by stringent measures should be made to reduce the variability, and cautions be exercised to interprete the results. the variability, and cautions be exercised to interprete the results.