TRANSIT-TIME ANALYSIS OF FORCED EXPIRATORY VITAL CAPACITY IN CYSTIC-FIBROSIS

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Abstract
Transit time analysis of the forced expiratory vital capacity maneuver was applied to 37 patients with cystic fibrosis 8-22 yr of age. This analysis divided the vital capacity into segments of air and assigned a transit time to each segment. The characteristics of the distribution of these transit times were used as measurements of pulmonary function. The quantities were compared with the forced vital capacity, 1-s forced expiratory volume, ratio of 1-s forced expiratory volume to vital capacity, peak flow, forced expiratory flow during the middle half of the forced vital capacity, maximal expiratory flow at 25% of the vital capacity, specific airway conductance and arterial PO2 [O2 tension] of these patients. The standard deviation of the transit times was the most frequently abnormal. The mean transit time had the largest range of values in terms of its own standard deviation, and it was the best single estimate of over-all lung function because it correlated almost equally with large and small airway function. The coefficient of variance of transit times was specific in detecting abnormality of small airways and was as sensitive in the detection of minimal lung disease as the standard deviation of transit times.

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