68 General Discussion 



problem, it really is a cardiovascular one rather than a respiratory one, 

 although of course the two are very close to each other wlien you come 

 to the pulmonary capillaries. I don't think such work has been applied 

 to ageinjj". 



Franklin: Could you elaborate on the mixing of air in the lunys? I ask 

 because in some (aniesthetized) animals there is a very uneven distribu- 

 tion of air in the lungs. In the rabbit, for instance, you get a very 

 patchy distribution, and in the cat to a lesser extent. In the human 

 subject it is even, according to your evidence, isn't it? 



Christie: Unfortunately you have mentioned two animals I know 

 nothing about. In dogs it is even. In human beings it is 80 per cent 

 efficient, very even indeed. Any ventilation engineer would be extremely 

 pleased if he could duplicate what we do with our lungs with every breath. 



Brull: Is there a sex difference in the strain and stress on the lungs? 



Christie: I think the sex distribution was indicated on the slides. 

 Most of the individuals we studied were men. It is a very curious thing, 

 and there is no clue as to why it should be, that emphysema occurs 

 almost solely in men. A woman can have chronic bronchitis, or asthma, 

 and yet she seems to be much more immune to this stress and strain 

 effect than man. But our figures are mainly on men, and therefore I 

 can't really say anything about the sex distribution. 



Franklin: Prof. Verzar, some years ago you showed the effects of 

 lowered oxygen partial pressure, which produced a change very similar 

 to one of ageing, namely, a greater resting degree of expansion of the 

 lungs. Could you correlate that with what we have heard this morning? 



Verzar: We believe that there is a third form of respiration regulation, 

 besides the depth and the rhythm of inspiration, and that is the increase 

 of respiratory surface by an increase of lung volume. One observes it 

 immediately if one starts physical work, or if the oxygen pressure in the 

 inspired air is decreased. One can demonstrate it by body plethysmo- 

 graphy. The meaning of the reaction is an increase of respiratory 

 surface by better ventilation. This reaction might decrease with old age, 

 by a decrease of muscle tone, and perhaps by a decrease of elasticity of 

 the lung. 



Christie: Well, there are many complex facets to this, but I think the 

 fundamental point is how much air you can bring into contact with the 

 pulmonary blood. This is a thing which should be investigated in regard 

 to age; unfortunately it will mean quite a lot of work. But it is true that 

 with carbon monoxide you can measure approximately the maximum 

 amount of blood which you can bring into contact with the alveolar air. 

 Normal individuals can double this, and it seems likely that athletes can 

 treble or quadruple it. This clearly is a thing that should be investigated 

 with advancing years — ^it really is the crux of the problem. 



Tunbridge: Is there any evidence from the work that Pugh did on the 

 Everest expedition that the Sherpas have a similar ability? 



Christie: I don't know. 



