Comparison between peak expiratory flow and FEV1 measurements on a home spirometer and on a pneumotachograph in children with asthma

Background: The accuracy of electronic portable home spirometers has been demonstrated in vitro using computer-based waveforms. We assessed the agreement in vivo between measurements of lung function on an electronic spirometer (Koko Peak Pro) and those obtained by the gold standard, a hospital lung function laboratory pneumotachograph. Methods: Fifty stable asthmatic children (33 boys), aged 6-17 years, performed peak expiratory flow (PEF) and forced expiratory volume in 1 see (FEV1) measurements according to international guidelines on a portable home spirometer and on the hospital pneumotachograph in random order. All measurements complied to standard quality criteria. The PEF and FEV, values recorded with the home spirometer and on the hospital pneumotachograph were compared. Results: All children performed reproducible high-quality measurements on both spirometers. PEF values on the home spirometer were considerably lower than on the laboratory pneumotachograph (95% CI for difference in PEF 14-30 L/min; P<0.0001). Individual differences in PEF between the two devices could be >100 L/min. The FEV1 values were slightly, but significantly, lower on the home spirometer (95% CI for difference in FEV1 0.02-0.1 L; P 0.0018). Conclusions: A home spirometer provides reproducible and quality acceptable measures in children with asthma when performed under professional supervision and encouragement. Mean PEF and FEV, values recorded on this home spirometer are significantly lower than those on a hospital pneumotachograph, and individual differences may be large. Therefore, home spirometry may not be interchanged with pneumotachography in a lung function laboratory.