Source: Annual Congress 2004 - Lung function technology: beyond the basic test
Disease area: Airway diseases

Abstract

The outcome of an expiratory manoeuvre is partially influenced by dynamic compression of the airways with greater airway collapse seen in those with severe airflow obstruction (ie.emphysema). In such patients, dynamic compression can occur during both tidal breathing (expiratory flow limitation, EFL) and also relaxed vital capacity measurements. It has been observed that measurements of Inspiratory Vital Capacity (IVC) with Expiratory Vital Capacity (EVC), despite operator and patient’s best efforts, are often different whereas in healthy subjects there is little difference. We hypothesized that the degree of this difference may be related to the degree of airflow obstruction and airway collapse and that the IVC-EVC measurement could be a useful method of detecting airflow limitation in patients with small airway disease. Measurements of FEV₁% predicted, FEV₁/FVC, IVC and EVC, were obtained from a group of 26 patients with proven alpha-1-antitrypsin deficiency and airflow obstruction.
The overall average (sd) difference in IVC-EVC was 220 ± 113 ml. When the data was analysed after sorting by FEV1/FVC% and comparing the more obstructed subjects (MO) values with the less obstructed (LO) there was no significant difference in IVC-EVC. (mean [sd] mo, 221 [121] ml Vs. lo, 217 [105] ml, p>0.005, NS).
In conclusion, the effectiveness of the combined IVC-EVC relaxed vital capacity measurement in the assessment of airflow limitation is not as clinically significant as established measures of airflow limitation in alpha-1-antitrypsin deficiency.

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N. M. John, J. Shakespeare, B. G. Cooper, R. A. Stockley (Birmingham, United Kingdom). An investigation into the usefulness of combined relaxed inspiratory and expiratory vital capacities in expiratory flow limitation. Eur Respir J 2004; 24: Suppl. 48, 2493

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