Reproducibility of spirometric measurements in normal subjects.

Several reports have described the reproducibility of measurement of the vital capacity in man (1-5), but with the exception of a study by Griffith and co-workers ( 4), the observations have not extended more than a few weeks. Similar data exist for the maximal voluntary ventilation (3, 6-8) and maximal midexpiratory flow rate (9) also based on observations a few hours or days apart. None of these studies has compared the reproducibility of spirometric data in smokers and nonsmokers. In this clinic, routine spirograms were done at intervals of 6 months to 4 years in a group of normal industrial workers exposed to low concentrations of beryllium. These figures were analyzed to determine the long-term reproducibility of the various spirometric measurements.