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462 INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE S> made either with Fleisch's 3 apparatus or Hochrein's.4 A description and a discus sion of both these instruments have been presented in previous reports. None of the measurements made by these investigators were obtained during work, since their equipment was not flexible enough to permit such measurements. inspi rang infoi Altitude Measurements.--Fleisch 5 used his apparatus to make measurements on a few subjects at various altitudes but presented few data. Hall and Wilson 6 .k published data on maximum and mean air flow measurements during inspiration at consi various altitudes. Pappenheimer and Lilly 7 described an instrument for measuring ' recoi ; resis inspiratory and expiratory air flow at altitude but showed only a few typical curves. balai A brief description of their apparatus was given in a recent report. Other service . appa investigators 8 have developed apparatus for inspiratory air flow measurements at : repo altitude, but no data concerning their subjects are presented. Previous Work in This Laboratory.--Our first investigation 9 led to publication of inspiratory data on several sedentary and working subjects at various work rates without and with resistance to breathing; Inspiratory and expiratory measurements at 830 kilogram-meters (Kg.-M.) (6,000 foot-pounds [f.-p.]) per minute and 1,107 Kg.-M. (8,000 f.-p.) per minute with minimal inspiratory and expiratory resistance and with resistance conditions equivalent to those of service gas masks were obtained in this laboratory by Silverman and co-workers.10 Measurements at 830 Kg.-M. and 415 Kg.-M. over a wide range of resistance conditions were presented in a report on allowable resistance to breathing.11 The present article presents both 3. Fleisch, A.: Der Pneumotachograph: Ein Apparat zur Geschwindigkeitsregistrierung der Atemluft (The Pneumotachograph: An Apparatus for Registration of Velocity of Respira tion), Arch. ges. Physiol. 200:713-722, 1925. 4. Hochrein, M.: Ueber Pneumotachographie (Concerning Pneumotachography), Arch, ges. Physiol. 210:753-760, 1928. 5. Fleisch, A.: Die Atmungsmechanik bei vermindertem Luftdruck (The Mechanics of Respiration with Reduced Air Pressure), Arch. ges. Physiol. 214:595-611, 1926. 6. Hall, F. G., and J. W. Wilson: Effects of Physical Activity and of Simulated Altitudes on Pulmonary Ventilation, Maximal Inspiratory (Peak) Flow and Pressure in Relation to Oxygen Requirements, J. Aviation Med. 15:160-166, 1944. 7. Pappenheimer, J. R., and J. C. Lilly: Measurements of Inspiratory and Expiratory Air Velocities at Altitude, Report 208, Committee on Aviation Medicine, National Research Council, November 1943. (Open.) 8. Hull, W. E.: Optical Flow Meter, Report 275, Committee on Aviation Medicine, National Research Council, January 1944. (Open.) Weatherby, J. H., and A. S. Burt: Peak Rates of Oxygen Flow from Oxygen Supply Systems: Description of a Low Inertia Flowmeter, Project X-324 (Av-185-f), Naval School of Aviation Medicine, Pensacola, December 1944. Watts, D. T., and F. W. Cherry: Recording Instrument to Measure Flow and Flow Resistance of Air-Oxygen Mixtures--Development and Test of (Laboratory Model), Project TED NAM25468, Navy Department, Bureau of Aeronautics, December 1944. 9. Silverman, L.; Lee, R. C.; Lee, G.; Drinker, K. R., and Carpenter, T. M.: Fundamental Factors in the Design of Protective Respiratory Equipment : Inspiratory Air Flow Measure ments on Human Subjects'With and Without Resistance, Report 1222, Office of Scientific Research and Development, United States War Research Agency, January 1943. Lee, R. C., and Silverman, L.: An Apparatus for Measuring Air Flow During Inspiration, Rev. Scient. Instruments 14:174, 1943. 10. Silverman, L, and co-workers: Unpublished' data, 1944. 11. Silverman, L.; Lee, G.; Yancey, A. R.; Amory, L.; Barney, L. J., and Lee, R. C.: Fundamental Factors in the Design of Protective Respiratory Equipment: A Study and an Evaluation of Inspiratory and Expiratory Resistances for Protective Respiratory Equipment, Report no. 5339, Office of Scientific Research and Development, United States War Research Agency, May 1945. Sut I ( S I ] ] ] ] Ex Ha 16 Kg in tat no se< co: 83 (a tai ex je- R