Evaluating the use of a portable spirometer in a study of pediatric asthma

Study objectives: Laboratory-based spirometry is the "gold standard" for the assessment of lung function, both in clinical and research protocols. These spirometers, however, are neither practical nor affordable for home-based monitoring or studies that collect data in multiple locations. Traditionally, peak flowmeters have been used, but they have important limitations. Design: Based on data from a cohort of 92 children with asthma, we evaluated the agreement between a portable spirometer and a office-based spirometer, using an in-line technique to evaluate measures from the same effort. We compared a range of pulmonary function parameters collected during office-based tests, and also evaluated whether adequate adherence and data quality could be achieved in a home-based study of children with asthma. Results: The agreement between the devices for the actual values of peak expiratory flow, FEV1 and forced expiratory flow at 25% of FVC was excellent. The portable device was programmed with customized software to grade each curve using revised American Thoracic Society acceptability and reproducibility criteria. For 74% of the curves, quality grade agreed with a grade assigned by physician review of the curve from the office-based spirometer. During 2 weeks of twice-daily monitoring at home, children completed an average of 23 of 28 possible sessions (83%). Of these, 84% had at least two acceptable and two reproducible curves. Although children greater than or equal to 8 years old were not more adherent, they were significantly more likely to achieve acceptable and reproducible curves. Conclusions: Portable spirometers can provide measurements that are highly comparable to those obtained from "gold standard" laboratory spirometers, and high-quality tracings can be achieved both at home and in the office setting. Visual inspection of the curves by experienced reviewers identified unacceptable curves that were not rejected by the quality control software. Portable spirometers are an important contribution to epidemiologic and clinical studies that require frequent measures of a more broad range of pulmonary function parameters than can be provided by peak flowmeters.