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PubMed · 517856

Forced expiratory spirometric parameters derived by feature-extraction techniques.

R L Pimmel·M J Tsai·J F Donohue
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Abstract

Spirometric data from 200 patients seen in the pulmonary function laboratory were analyzed retrospectively. Using standard criteria, the spirometric patterns of the subjects were classified as indeterminate, normal, restrictive, or obstructive; obstruction was further classified as mild, moderate, severe, or very severe. A formal feature-extraction technique was used to define 2 new parameters. These were linear combinations of the 5 standard spirometric parameters and explained 94% of the variation in the original parameters. The derived parameters provided better separation of the various classes than the combination of the normalized forced vital capacity and the ratio of the forced expiratory volume in 1 s to the forced vital capacity.

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Forced Expiratory Flow RatesForced Expiratory VolumeHumansLung Diseases, ObstructiveRetrospective StudiesSpirometryVital CapacityJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.

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R L Pimmel, M J Tsai, J F Donohue. 1979. Forced expiratory spirometric parameters derived by feature-extraction techniques.. https://doi.org/10.1164/arrd.1979.120.6.1245

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Expiratory flow limitation detected by forced oscillation and negative expiratory pressure.

The within-breath change in reactance (Delta(rs)) measured by forced oscillation technique (FOT) at 5 Hz reliably detects expiratory flow limitation in chronic obstructive pulmonary disease (COPD). The present study compared this approach to the standard negative expiratory pressure (NEP) method. In total, 21 COPD patients were studied by applying both techniques to the same breath and in 15 patients the measurements were repeated after bronchodilator. For each patient and condition five NEP tests were performed and independently scored by three operators unaware of the FOT results. In 180 tests, FOT classified 53.3% as flow limited. On average, the operators scored 27.6% of tests flow limited and 47.6% non-flow limited, but could not score 24.8%. The methods disagreed in 7.9% of cases; in 78% of these the NEP scores differed between operators. Bronchodilation reduced NEP and DeltaX(rs) scores, with only the latter achieving significance. Averaging the operators' NEP scores, a threshold between 24.6-30.8% of tidal volume being flow limited by NEP produced 94% agreement between methods. In conclusion, when negative expiratory pressure and forced oscillation technique were both available they showed good agreement. As forced oscillation technique is automatic and can measure multiple breaths over long periods, it is suitable for monitoring expiratory flow limitation continuously and identifying patients' breathing close to the onset of expiratory flow limitation, where intermittent sampling may be unrepresentative.

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