95. MECHANICS OF BREATHING (Continued) 



Part IV: INTRAPLEURAL PRESSURES: MAN 



Values expressed as gauge pressures (cm of H2O less than ambient atmospheric pressure). 



/I/ Measurements made with a modified Lillingston and Pearson pneumothorax apparatus. 



Contributors : (a) Lees, W. M., Snider, G. L., and Fox, R. T., (b) Radford, E. P., Jr. 



References : [ 1] Lees, A. W., Glasgow M. J. 32:1. 1951. [ 2] Laha, P. N., Ind. M. Gazette 81^:359, 1946. 



Part V: COMPLIANCE OF LUNG-THORAX SYSTEM: MAMMALS 



Contributors : (a) DuBois, A. B., (b) Ross, B. B., (c) Radford. E. P., Jr., (d) Frank, N. R. 



References : [l] Niras, R. G. Conner. E. H.. and Comroe. J. H.. Jr.. J. Clin. Invest. 34:744. 1955. [2] Rahn, H., 

 Otis. A. B.. Chadwick, L. E., and Fenn. W. O.. Am. J. Physiol. r46: 161. 1946. [3] Otis. A. B., Fenn. W. O.. and 

 Rahn. H., J. Appl. Physiol. 2:592. 1950. [4] Nisell. O. I., and DuBois. A. B.. Am. J. Physiol. 178:206. 1954. 

 [5] Brody, A. W.. ibid^28 = '89, 1954. [6] Brody. A. W.. DuBois. A. B., NiseU, O. I., and Engelberg. J., ibid 

 286:142. 1956. [7] Van Lie w. H. D., ibidr77:161, 1954. [8] Severinghaus. J. W.. and Stupfel. M.. J. Appl. 

 Physiol. 8:81. 1955. [9] Bernstein. L.. J. Physiol. J_23:44P. 1954. 



Part VI: RELAXATION PRESSURE CURVE: MAN 



The relaxation pressure curve (solid 

 line) of the chest and lungs (Pq + Pl) 

 consists of two components (broken 

 lines), the elasticity of the chest and 

 diaphragm (Pp) and the elasticity of 

 the lungs (Pl). At the normal relaxa- 

 tion volume, where the relaxation pres- 

 sure curve crosses the axis, the 

 elasticity of the lung is exactly bal- 

 anced by the elasticity of the chest, and 

 both are equal in magnitude to the 

 intrapleural pressure, or 4 mm Hg at 

 expiration. The lung curve intersects 

 the relaxation pressure curve at a 

 volume of about 70% of the vital capac- 

 ity, at which point the chest curve 

 crosses the axis and all of the relaxa- 

 tion pressure is due to the elasticity 

 of the lung. The lung curve presum- 

 ably intersects the "0" axis in the 

 residual air region at a point that 

 measures the minimal air. 



Contributors : (a) Fenn. W. O., 

 (b) Radford, E. P.. Jr. 



Reference : Fenn. W. O. . in "Handbook 

 of Respiratory Physiology" (Boothby, 

 W. M.. ed). Randolph Field. Texas: 

 USAF School of Aviation Medicine, 

 1954. 



100 



80 



60 



a 

 U 



40 



^ 20 



Resting Position 

 of Chest 



-20 



Pulmonary Pressure, mm Hg 



135 



