抄録
Recently, it has been demonstrated that the conventional lung function tests are too insensitive to detect the earlier stages of airway diseases and various methods have been devised to detect the diseases in their earlier stage. The measurement of closing volume has turned out one of a sensitive indicator of small airway diseases which are considered as early manifestation of chronic obstructive lung diseases. Therefore, we measured the closing volume and evaluated its methodology and clinical usefulness.
Material and method.
Measurements were made in 34 non-smokers with age ranged from 18 to 61 years and 17 smokers with age ranged from 26 to 61 years. None of the non-smokers had a history of respiratory diseases or of any repiratory symptoms. The closing volume was measured with the subjects in seated and supine positions using a bolus of argon. The method consists of having subjects expire maximally to the full expiration and, at the outset of inspiratory phase, injecting small bolus of argon into the mouth piece. Subjects then make a slow vital capacity expiration with mean speed of less than 0.5L/sec. The argon concentration in the expired gas and the volume expired are continuously measured by mass-spectrometer and recorded on both mingograph and storage oscilloscope. At least three measurements of closing volume were made in each subject in both position studied and the mean of three values of each measurement is taken as the final value. Methodologically special care was taken to determine the proper amount of inhaling bolus. Results and summary are as follows;
1) For measurement of closing volume with argon gas method, about 2 to 8% of each vital capacity may be proper as the volume of inhaling argon gas.
2) In both seated and supine non-smokers the percentage rate of closing volume to vital capacity increased linearly with age and regression equation, Y=1.8+0.37×Age was obtained at the sitting nonsmokers.
3) As to the effect of position on closing volume, percentage rate of closing volume to vital capacity had a tendency to be higher in the supine position than in the sitting.
4) Percentage rate of closing capacity (closing volume+residual volume) to total lung capacity had a similar tendency as closing volume to vital capacity rate as a function of age.
5) Higher value of closing volume was obtained in smokers than in non-smokers but the difference of closing volume between those was not remakrable compared with the values obtained in the investigators in the foreign countries.
