The quality of home spirometry in school children with asthma

Background-Handheld electronic spirometers provide the opportunity for more comprehensive monitoring of lung function at home than has hitherto been a vailable. The aim of this study was to assess the quality of spirometric da ta collected at home by 90 asthmatic schoolchildren aged 7-14 years. Methods-After training, children carried out twice daily recordings at home for four consecutive periods of 4 weeks using a data storage spirometer (V italograph), encouraged by 4-weekly visits from a research nurse. Complianc e (proportion of blows recorded at correct time of day), technical quality (by machine criteria), and valid data recorded (the multiple of compliance and technical ability) were assessed. Results-Mean compliance declined from 81.4% to 70.4% (p<0.001) between the first and last month, although the technical quality of the manoeuvres (81. 9% and 80.1%, respectively) did not change significantly (p=0.48). Conclusions-There was a steady reduction of valid data over the four period s (from 73.6% to 64.3%, 59.7%, and 57.6%) with wide individual differences. Even under ideal conditions, home spirometry provides an incomplete land t herefore potentially biased) picture of long term changes in pulmonary func tion.