66 General Discussion 



this which is responsible for the changes with advancing years, which 

 are in the same direction as emphysema. Occasionally emphysema will 

 develop in old age without chronic bronchitis or asthma, in fact I think 

 one of Dr. Vischer's cases, the woman of onc-hundred-and-two, did have 

 emphysema, and Prof. Cameron said that quite a few of his old people 

 had emphysema. We have calculated from our results that if a healthy 

 individual were to live on indefinitely and the changes in his lungs 

 progressed at the rate we have observed, he would develop emphysema 

 at the age of one-hundred-and-forty. 



Shock : In collaboration with Dr. Milton Landowne and Mr. Arthur 

 Norris, our laboratory has been collecting observations on age changes 

 in pulmonary function. We have also used a helium wash-out technique 

 for estimation of the various lung compartments (Norris, Landowne and 

 Shock, 1952, Fed. Proc, 11, 114). The study is still in progress, but I 

 have tabulated the results of our determinations made on ten subjects 

 per decade, from age twenty to age ninety. The values are tentative, but 



1 believe the trends observed with age can already be seen in this group 

 of 70 subjects. All of the subjects tested were ambulatory and gave no 

 clinical evidence of respiratory impairments. The greatest age change 

 was found in estimates of maximum voluntary ventilatory capacity. 

 The average value was about 125 l./min. for our twenty- to thirty-year- 

 olds and 50 l./min. for our eighty- to ninety-year olds. The maximum 

 inspiratory capacity fell from about 3-8 1. at age twenty to thirty to 



2 • 1. at age eighty to ninety. The inspiratory reserve volume also fell 

 from about 3 -5 1. to 1 -8 1. over the same age range. The age decrement 

 in expiratory reserve volume was not nearly as great — 1 -1 1. at age 

 twenty to thirty to • 5 1. at age eighty to ninety. All three of the above 

 fimctions showed a curvilinear relationship with age in contrast to the 

 linear fall in maximum voluntary ventilatory volume. The mean values 

 for functional residual capacity and residual volume were still somewhat 

 irregular, but there was little evidence of any systematic change with 

 age in functional residual capacity, whereas the residual volume showed 

 some tendency to rise with age. Finally, we found a gradual reduction 

 in total lung volume (6-2 1. at age twenty to 5 -0 1. at age eighty). After 

 the age of sixty, there was little change in total lung capacity. In 

 contrast, the vital capacity continued to decrease up to the age of eighty. 

 I think that in general the results we obtained are in agreement with the 

 cases Dr. Christie has reported. 



We have not done carbon monoxide measurements, and I'd like to ask 

 Dr. Christie how one can separate the effects of the exchange of carbon 

 monoxide from any changes that might occur in cardiac output with age. 



Christie: All this work has been done in conjunction with Comroe in 

 Philadelphia and Roughton in Cambridge. I think it is true that the 

 speed of blood flow through the lung will make practically no difference 

 to this measurement. What does affect it is the actual area of blood 

 exposed to the alveolar air. So we are measuring the actual contact of 

 the air with the pulmonary blood. Our work on patients with mitral 

 stenosis shows that they do not get the same reduction of CO uptake 

 although the cardiac output is decreased. 



