95. MECHANICS OF BREATmNG (Continued) 



Part U; INTRAPULMONARY PRESSURES AT VARIOUS LUNG VOLUMES: MAN 



All measurements made on males in sitting position. Mean lung volumes are per cent of vital capacity at ambient 

 pressure. Values in parentheses are ranges, estimate "b" of the 95% range (cf Introduction). 



/I/ Measured with glottis open at desired lung volume; one nostril plugged and other connected with a water 

 manometer. 



Contributors : (a) Lees, W. M., Snider, G. L., and Fox, R. T., (b) Radford, E. P.. Jr., (3) Dayman, H. G. 



References : [ l] Rahn, H.. Otis, A. B., Chadwick, L. E., and Fenn, W. O., Am. J. Physiol. 146:161, 1946. 

 [2] Gross. D., Am. Heart J. 25:335, 1943. 



Part UI: PRESSURE- VOLUME DIAGRAM OF CHEST AND LUNGS: MAN 



On the ordlnates 100% of vital capacity represents the height of inspiration, and 0% of vital capacity represents 

 maximum expiration, both at zero pressure or ambient pressure in the lungs. The diagram shows the pressures 

 which can be developed passively (relaxation pressure) or actively (maximum pressures) at different lung volumes. 

 In the upper right corner where the lung is maximally expanded and the pressure has a positive value, there is 

 danger of rupture of the lung (broken line in diagram). In the lower left corner where the blood vessels are exposed 

 to a maximum negative pressure, there is extreme vasodilation and danger of hemorrhage (broken line in 

 diagram). 



100 r 



> 



-100 



-80 



-60 



-40 -20 20 40 



Pulmonary Pressure, mm Hg 



Contributors : (a) Fenn, W. O., (b) Radford, E. P.. Jr. 



References : [ l] Fenn, W. O., in "Handbook of Respiratory Physiology" (Boothby, W. M., ed), Randolph Field, 

 Texas: USAF School of Aviation Medicine, 1954. [2] Fenn, W. O., Rivista Di Medicina Aeronautica, 1955. 



134 



