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DISCUSSION 
J. R. Gillespie, University of California, 
Davis: I was wondering why you didn't con- 
sider increases in left atrial pressure as a possi- 
ble explanation for recruitment? 
W. Wagner: I should have mentioned that. 
We measured left atrial pressure and as has 
been the typical finding with hypoxia, there 
was not an increase in left atrial pressure in 
these animals. 
J. Reeves, University of Kentucky, 
Lexington: That is indeed a very beautiful 
movie and I'm impressed by the technical 
achievement of getting such pictures. It is per- 
plexing to see the same amount of blood going 
through a few channels during normoxia as go 
through a great many channels during hypoxia. 
I wonder how you account for the fact that vir- 
tually all of the channels in the lungs seem to be 
open during hypoxia and yet the total flow is 
the same, or virtually the same ? 
W. Wagner: One of the things that we are 
currently not able to do technically, is quan- 
titate the velocity of the red cells. It may well be 
that although we see flow in these vessels, the 
velocity could be lower. I agree this is a prob- 
lem. In some cases, of course, there was a 
change; an increase in cardiac output. The 
cases we saw in the film where it demonstrates 
recruitment the best were accompanied by in- 
creases in cardiac output. At other times, new 
vessels will open, but the flow is rather sluggish 
through them. 
D. C. Sawyer, Michigan State, East 
Lansing: Were these untrained dogs or anes- 
thetized dogs? 
W. Wagner: These animals are asleep 
throughout the procedure. 
Dr. Sawyer: Asleep with what? What agent 
did you use? 
W. Wagner: Alpha-chloralose. 
R. H. Redding, Brown University, Provi- 
dence, Rhode Island: This was a very elegant 
demonstration visually. One thing occurred to 
me, and it may be very simple. I'm sure you 
have an answer. In measuring your cardiac out- 
put, if you used a simple oxygen consumption 
principle, you may well not have measured the 
shunting of blood which wouldn't show up in 
your cardiac output. 
W. Wagner : These measurements were 
made with green dye. 
Dr. Redding: Was there much shunting? 
Did you notice a quick return of the dye? 
W. Wagner: We didn't look specifically at 
shunting, so, unfortunately, I can not give you 
an adequate answer. 
Chairman Lenfant: Dr. Wagner, I wonder 
if you are aware of a paper which was pub- 
lished in the "Journal of Clinical Investigation" 
in November or December which reported expe- 
riments studying the site of the effect of hy- 
poxia? Some very elegant experiments were re- 
ported in this paper by Murray and Blazier 
from San Francisco. They reached a conclusion 
which is quite similar to yours. 
W. Wagner: I didn't know about that 
paper. Since we have come up with a somewhat 
unorthodox explanation for our findings, I am 
delighted to hear of similar conclusions arrived 
at by independent techniques. 
