Discriminant analysis of pulmonary function parameters. Healthy adults versus mild asthmatics and moderate asthmatics.

Volume-time (V-T) and flow-volume (F-V) curves were measured in all the subjects of nonsmoking young males (mean value 26.3 yrs. of age), healthy and asthmatics. Eleven parameters of pulmonary function tests composed of two V-T, six F-V, and three mean time constant (MTC) parameters, were calculated from the curves. These parameters were used in the two analyses through the all possible selection procedure (APSP) discriminating between healthy adults and mild asthmatics and also between healthy and moderate. Flow rate at 75% of FVC (V75) proved to be the most useful parameter and V50 the next best in both analyses. The probability of misclassification using all eleven parameters was 19.64% in the analysis of healthy adults and mild asthmatics, and 4.29% in the analysis of healthy adults and moderate asthmatics. There was a little difference in the parameters selected at every step. The discriminant analysis proved that the flow-volume patterns were different according to the severity of bronchial asthma. Thus flow-volume recognition was considered to be important in analyzing the severity of bronchial asthma.