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Closing volume in healthy non-smokers

1973; Elsevier BV; Volume: 67; Issue: 1 Linguagem: Inglês

10.1016/0007-0971(73)90003-x

1878-2426

J.V. Collins, T. J. H. Clark, S. McHardy-Young, G.M. Cochrane, J Crawley,

Respiratory Support and Mechanisms

‘Closing volume’, defined as that lung volume at which the dependent lung zones ceases expiration, was measured in 41 healthy non-smokers aged seventeen to sixty-nine years using xenon-133. Subjects were studied erect before and after inhalation of a β-adrenergic bronchodilator aerosol and in 31 subjects the studies were repeated in the supine position. Results in individual subjects showed good reproducibility. The regression with age and standard deviation of the measurements were similar to previous reports and no change was observed after inhalation of bronchodilator. The relationship of Phase 4 to vital capacity was unaltered by change in posture. It is suggested that the use of standard deviation (i.e. ± 2 SD) to define the limits of a normal range may be unduly optimistic. Tolerance limits to include 95% of healthy subjects calculated from studies of this size would provide unacceptably wide ranges for epidemiological purposes if the technique were introduced as a screening test for early disease of small airways. It is suggested that further developmental studies are required.