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Richard DeWall:
Transcript of Interview Excerpt

Richard DeWall, interviewed by David Rhees on October 28, 1998 at The Bakken Library and Museum, Minneapolis, Minnesota.

Then I fixed a vent at the top of it to let the gas off of it but still keeping it pressurized. That way I could have a flow of oxygen that had three atmospheres of pressure to this exposed film of blood. Of course, to have it in a long hose and climb the hose to about thirty or forty degrees so the blood would run down it. I didnt have to pump it down or anything else; it would just flow down by gravity, and kept the lower third of this tube full of blood in order to have a reservoir to pump it out, because if you kept it right down at the bottom, you might pump out air. So you had to have a reservoir at the bottom that you could control in order to evacuate the tube as your oxygenation was completed. Of course, the vent at the top was not only to decompress the oxygen, but to vent off the excess carbon dioxide. So it was to carry out essentially respiratory, most of the respiratory needs of the blood, for that short-term purpose.

I was able to do that. I had the system working pretty well, except the problem came that when I decompressed the oxygen to go into the animal, the whole thing would end up with a little bubbling, because your oxygen would come out of the serum and it would bubble. But then I noticed that as it was being decompressed, when I took the pressure off the system, the bubbles would rise to the top of the layer of blood in the reservoir and the reconstituted blood would slide underneath. Of course, bubbles within the blood had a lighter density than reconstituted blood, so it would float. So it would actually skim it off, just a separator.

So then I figured, well, if youre going to have to deal with bubbles, might as well learn how to live with them. So, using that as a concept, this long hose as a bubble trap, I thought, well, Ill just blow some oxygen into the blood and bubble it in the ordinary fashion. I think this is fortuitous also, because a lot of the previous bubblers had used micro bubbles, putting oxygen through so-called sintered glass filters. So youd just get a foam being produced, and thats much more difficult to deal with than large bubbles. So I took, I think it was either twenty-two or twenty-three hypodermic needles and put about fifteen of them through an ordinary black laboratory cork and fixed a little chamber that I could just pump oxygen under ordinary pressure through these needles and, of course, put that cork into the bottom of a long vertical tube and that would be my bubbler, the oxygenator. That way I could get the blood into it. Then Id dump it all into this inclined hose, but being seven feet long, six feet, whatever it was, it was clumsy, so I just put it in a coil, which was the same difference. So thats how the helix came about.

 

Biographical Information

Richard DeWall was born attended school and college in Minnesota. He developed the bubble oxygenator, a temperature controlled oxygenator, and a capillary type oxygenator. He helped found a medical school and heart surgery program at an Ohio university. He has since retired.

Richard DeWall