Partial effective times of the forced expiratory spirogram in health and mild airways obstruction

The partial effective times of the expiratory spirogram were calculated in 80 normal non-smoking subjects aged from 20 to 69 years and in 30 patients aged from 30 to 58 years with chronic bronchitis. Of these patients, 28 had a normal FEV1/FVC ratio, while the other two had a low ratio. Partial effective times were calculated for 10% segments of the expired FVC from total lung capacity (0% FVC) to residual volume (100% FVC) and became progressively longer after 50% of the FVC had been expired in normal subjects. The elongation to the partial effective times was more pronounced with age. In the patients with simple chronic bronchitis (normal FEV1/FVC ratio) the partial effective times were longer than normal after 50% of the FVC had been expired and after 10% of the FVC had been expired in the two patients with chronic bronchitis and low FEV1/FVC ratio. The partial effective times of the forced expiratory spirogram, especially that at the 80--90% part of the FVC, seem to be very sensitive indices for the early detection of mild airways obstruction.