674 
PHYSIOLOGY 
Table IV. — A comparison of values for selected parame- 
ters obtained by similar methods from Beagle dogs and 
human subjects at approximately the same altitude. 
Values for Beagles are taken from Table 1. Values for 
humans were obtained by duplicate measurements per- 
formed on 10 normal, adult, male subjects aged 17 to 
38 years* 
Parameter Mean 
Alveolar O2 tension 83 
Arterial O2 tension 75 
Alveolar-arterial O2 gradient 8 
Arterial CO2 tension 41 
Alveolar CO2 tension 37 
Arterial-alveolar CO2 gradient 4 
Arterial pH 7.38 
Specific ventilation 40 
Beagle Dog 
Human 
Range 
Mean 
Range 
71-97 
85 
77-100 
64-90 
73 
65-83 
1-15 
12 
3-24 
31-50 
36 
32-42 
27-45 
33 
28-39 
0-7 
3 
-2-6 
7.31-7.45 
7.45 
7.41-7.50 
28-57 
34 
24-60 
* Values provided by Dr. U. C. Luf t. Dept. of Physiology, Lovelace 
Foundation for Medical Education and Research, Albuquerque, N. M. 
though the difference from the younger group 
was not significant at the 95% level. Donevan 
et al.,21 using a steady state CO method, reported 
a lovi^er mean diffusing capacity in persons over 
35 than in those under 35. Other authors using 
various methods, reported similar findings.22-24. 
The finding of a significantly lower pul- 
monary compliance in the limited number 
of older dogs tested presents a contrast 
to changes in the compliance of human lungs re- 
ported to occur with aging. The elastic recoil of 
the lungs is lower in elderly persons than in 
younger subjects, resulting in an increase in 
pulmonary compliance with age.^^-^" This ap- 
parent species difference is unexplained at this 
time. 
The ease of performing pulmonary function 
tests on unanesthetized dogs and the usefulness 
of those tests in appraising pathophysiologic al- 
terations of dog lungs has been demonstrat- 
g(j27-3o rpjjg techniques described eliminate 
both the risk of anesthetic procedures and 
the variable changes in pulmonary function 
that may be related to anesthesia. The similari- 
ties observed between Beagle dog and human 
pulmonary function and in the changes of cer- 
tain function parameters with age indicate the 
usefulness of the Beagle dog as a model for 
studying a variety of research problems in the 
fields of pulmonary toxicology, lung aging, and 
general physiology of the lung. 
ACKNOWLEDGMENT 
The authors are grateful to Dr. U. C. Luft 
for his guidance during the development of the 
procedures described, to Mr. W. C. Nenno, Mrs. 
G. A. Morrison, and Mrs. P. B. Beckley for con- 
ducting the measurements, and to the technical 
staff who aided in the development and per- 
formance of the tests. 
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