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SILVERMAN ET AL.--A1R FLOW MEASUREMENTS ON HUMANS 463 inspiratory and expiratory measurements without and with resistance over a wider range of work rates. Respiratory exchange data were also obtained, since this information will be of value in assessing oxygen requirements at various work rates. EXPERIMENTAL MATERIAL AND METHOD Measuring Apparatus.--The measuring apparatus used for obtaining the data in this report consisted of an inspiratory and an expiratory flow-measuring instrument, a photographic recorder, the face piece of the United States Army chemical warfare service mask, a pair of low resistance (S-L) valves,12 known inspiratory and expiratory resistances, and a well counter balanced gasometer with minimal resistance. A schematic diagram of the complete measuring apparatus and a complete description of each component of the apparatus are given in a recent report.11 The bicycle ergometer described in that report was used to measure work rates. Table 1.--Physical Characteristics of Subjects Subject D. S. 0. S. N. V. F. P. H. B. McA. M. S. N. R. F. P. V. Occupational Record f Occupation Athletics' Student Student Student Student Student Student Student Student Student Student ' Student Student Student Med. student Student Med. student Research investigator Graduate student Track Track Track Track Track Crew Grew Crew Crew Crew Crew Track Track Crew Age, Tr. 17 17 18 18 18 18 18 18 19 19 19 20 20 20 22 23 28 30 Weight Height w Kg. Lb. Cm. Ft. In. 59.9 74.9 61.3 69.0 70.4 84.5 88.2 88.6 78.2 81.7 85.4 68.0 78.1 80.7 , 79.0 80.0 88.8 54.9 132 165 135 152 155 186 194 195 172 180 188 150 172 178 174 176 195 121 170 5 7 180 5 11 178 5 10 178 5 10 191 6 3 185 6 1 197 6 6 193 6 4 185 6 1 193 6 4 188 6 2 178 5 10 183 6 , . 180 5 11 185 6 1 183 6 183 6 173 5 8 Vital L.* 5.0 5.3 5.8 5.0 5.9 5.7 7.6 6.8 7.7 5.9 6.1 5.7 6.1 . 5.4 6.3 7.2 6.1 4.6 * Corrected to 37 C., saturated air, and observed pressure. Expired air was collected in the gasometer, and samples were removed and then analyzed by a Haldane gas analyzer. Subjects--The subjects used in these experiments were healthy males ranging in age from 16 to 44. To complete the series, data obtained at 415 Kg.-M. (3,000 f.-p.) per minute, 830 Kg.-M. (6,000 f.-p.) per minute and 1,107 Kg.-M. (8,000 f.-p.) per minute which were obtained in this laboratory10 and from a subsequent report11 are. included. The subjects listed in table 1 were subjects who performed the complete work series of this project and who were not listed in the reports just mentioned. Procedure.--This project consisted of a series of experiments ranging from a relaxed sedentary position to work on a Krdgh bicycle ergometer at 1,660 Kg.-M. An experiment was conducted with the subject seated on the bicycle and with the subject riding at 0, 208, 415, 622, 830, 1,107 1,384, and 1,660 Kg.-M. Each subject performed the series with minimal resistance (air flow-measuring apparatus only) and with 64 mm. inspiratory and 41.mm. expiratory resis tance. An additional experiment at 415 Kg.-M. was included with 64 mm. inspiratory and 27 mm, expiratory resistance. The number of subjects performing each experiment varied. Twelve sub jects completed the majority of the experiments, and dafa obtained in previous studies 13 were 12. Silverman, L., and Lee, R. C.: A Low Resistance Valve and Indicating Flowmeter for Respiratory Measurements, Science 103:537, 1946. 13. Silverman, footnotes 10 and 11.