J. L. MAUDERLY AND J. A. PICKRELL 
677 
scious dogs. The results are quite possibly dif- 
ferent. We haven't elucidated all these differ- 
ences at this point. We have simply chosen the 
model that we can v^^ork with for the reasons 
that I gave, and have done a fairly extensive job 
of establishing our own values for our own 
techniques in this model. Now there's nothing 
I'd like better than to be able to make some of 
these comparisons and I'm sure that we will, in 
the future. 
P. L. Luna, Armour Pharmaceuticals, Kan- 
kakee, Illinois: Have you had any problems 
with the saliva from these dogs when you exer- 
cise them ? 
Dr. Mauderly : No we have not. And I don't 
know whether this is because of the relatively 
short time that they're on the treadmill or 
whether it is because they are inspiring a dry 
gas. Of course, Albuquerque has a very low 
mean humidity and this may have something to 
do with it. There usually is moisture in the 
mask, but as I said, the mask is relatively 
square on the front and about 4 inches in depth 
and eliptical in shape. Therefore, any moisture 
that might collect, a few cc's, would be down at 
the bottom and would not interfere with gas 
collections. But it has not been a problem for us 
to this point. 
G. E. Bisgard, University of Wisconsin, 
Madison: What is your experience with the 
mass spectrometer? I've had people give me 
conflicting reports on having considerable diffi- 
culties keeping them in working order and so 
forth. How have you done with that? In our 
studies with calves, we've had problems getting 
good end tidal gas samples. We don't feel that 
we can get real good samples because of the 
sometimes fast respiratory rates, and we won- 
der about your experience with dogs in this 
area. 
Dr. Mauderly : Well, in relation to your first 
question about mass spectrometry, I think 
that's a little bit like marriage, in which you 
have great expectations and then for the first 
short period of time after you achieve this sta- 
tus, you have great doubts and then you settle 
down to where you are used to the equipment 
and you become a pretty handy repairman in 
the laboratory. Now, as you saw, we use the 
SRI mass spectrometer which has fixed collec- 
tors. It is a very simple machine. It's a very nice 
machine for laboratory work, easy for techni- 
cians to operate, and I'd say that we've had 
very good luck with it. Now before the advent 
of our mass spectrometer we were using indi- 
vidual analyzers of different types for the dif- 
ferent gases and I think those of you in the au- 
dience that saw the \sib at that stage can see the 
improvement. It has eliminated a tremendous 
problem in continuous calibration and so forth. 
I would say that our experience has been very 
good, although it's not optimal at this point. 
W. J. Moorman, National Institute of Occu- 
pational Safety and Health, Cincinnati, 
Ohio : What is the volume of the dead space in 
the mask that you use and do you think that 
this effects ventilation? My second question is: 
how reliable are your esophageal pressure trac- 
ings for the mechanics? So you use any kind of 
anesthesia or local anesthesia, or do you have 
esophageal comes ? Any problems with this ? 
Dr. Mauderly: Well, yes, of course, there 
are problems in any studies of this type and 
here again probably the only saving grace is 
that we're making these measurements over a 
period of several breaths and therefore we can 
recognize changes in the hysteresis loops that 
we see, and if we see something widely occur- 
ring, we can wait or calm the dog or try again. 
We use no local anesthesia or anything in plac- 
ing the catheters. The dogs take these very well. 
I am sure that there are some changes and I 
think when you see the data in the manuscript 
you'll recognize that we have fairly substantial 
standard deviations in our compliance measure- 
ments. We feel that the pressure fluctuations 
that we get are relatively reliable. Those static 
tests that we've done with the catheters and so 
forth have indicated this. We've noted in our 
different studies, where we've applied these 
tests, that the compliance measurements we've 
obtained have shown very nice changes compa- 
rable to those performed by other methods. All 
I can say at this point, is that it doesn't seem to 
be a problem. There are definitely variations 
that occur. In comparing the dog with baseline 
testing prior to entry on a study, if his meas- 
urements are outside certain limits, we'll retest 
him, and I think quite often the reason for these 
