IMPROVEMENT OF TIDAL BREATHING PATTERN-ANALYSIS IN CHILDREN WITH ASTHMA BY ONLINE AUTOMATIC DATA-PROCESSING

The time taken to achieve peak tidal expiratory flow as a proportion o f total expiratory time (t PTEF/t E) during tidal breathing (TB) is us ed as a parameter of airway obstruction in children with asthma, Curve selection bias is one of the most important limitations to the method , This study evaluates three curve selection methods, including a comp uter program, which on-line selects and analyses TB curves (Masterscre en Paediatric; Jaeger, Germany). TB analysis was performed in 26 child ren (aged 4-7 yrs) with asthma, before and after methacholine provocat ion and after subsequent bronchodilatation. Levels and stability of TB parameters derived from computer-selected, unselected and unbiased ey e-selected curves were compared. t PTEF/t E ratios of the computer-sel ected curves agreed well with the unbiased eye-selected curves (limits of agreement -4.8 and +5.8%), but were significantly different from t he ratios of unselected curves. Computer-derived t PTEF/t E ratios had the highest level of stability: the reliability coefficient of baseli ne measurements was 0.96 for computer selection, 0.84 for eye selectio n and 0.87 for no selection (reliability index = 1 at maximal stabilit y), Tidal volume, respiratory rate, inspiratory and expiratory time we re also assessed accurately by the computer program, The mean t PTEF/t E ratio (computer selection) dropped after methacholine provocation ( from 30+/-9 to 22+/-9% at provocative dose at which forced expiratory volume in one second had dropped greater than or equal to 20% from bas eline (FEV1-PD20 level), p<0.001) and was restored after bronchodilata tion (30+/-6%; p<0.001). We conclude that on-line computer analysis is preferable to no selection and to by-eye selection, The use of the pr ogram avoids curve selection bias and enhances the applicability of ti dal breathing analysis as a measure of airflow obstruction in young ch ildren.