266 LOADING UP 



It is well known that ballooning, for instance, causes respiratory 

 distress ; so, too, does mountaineering. Mountain sickness fre- 

 quently begins at altitudes of 2000 to 3000 metres, particularly if 

 the ascent has been fairly rapid by railway. Airmen usually suffer 

 after ascending 5000 to 6000 metres. The partial pressure of 

 oxygen in the blood as determined by the carbon monoxide method 

 has been found to be 35 mm. Hg above the oxygen pressure of 

 alveolar air. Considerable doubt exists, however, as to the validity 

 of this method. It depends on the careful matching of a carboxy- 

 lated blood with a blood-carmine mixture, and minute quantities 

 of blood are used. 



TABLEJXLV. 



EFFECT OF ATMOSPHERIC PRESSURE ON ALVEOLAR OXYGEN 

 TENSION. 



Height above sea O 2 tension of Alveolar O..> tension, 

 level in metres. air. mm. Hg. mm. Hg. 



Berlin 54 157 105 



Brienz 500 148 88 



Brienzer Rothorn - 2130 121 62 



Cold'Olen 2900 110 60 



Monte Rosa 4560 89 61 



One fact in the data given by those investigators is a little 

 strange although it may have no significance. Notwithstanding 

 that the arterial oxygen tension was always higher than that 

 given for the alveolar air, it was never higher than that of the 

 atmosphere at the time, although occasionally not much below it. 

 Why should the secretory power fail just at this level and not 

 raise the oxygen tension above that of the atmosphere ? Is 

 it possible that the blood had come into equilibrium with an 

 oxygen tension which was not given correctly by the measurement 

 of that of the alveolar air ? Might it not also be possible that 

 the carbon monoxide method gives different values when the 



