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The final answer to my dumb question which essentially was: "I understand that O2 can be carried in blood both bound to hemoglobin and dissolved to saturation, but since there's got to be way more dissolved than we can use, how come we don't get bent from it"? Answer below from a diving doc working at DCIEM. Thanks for the connection Maureen. Cam ---------- From: Maureen Lunney <melunney@sy*.ca*> Reply-To: melunney@sy*.ca* Date: Wed, 26 Sep 2001 13:41:52 -0400 To: cam@ca*.co* Subject: [Fwd: O2 bends] Mr. Banks: Dr. Sawatzky has given his permission to post his answer with his name attached. From: "Sawatzky, David" <David.Sawatzky@dc*.dn*.ca*> Date: Monday, September 24, 2001 1:14 PM To: "'melunney@sy*.ca*'" <melunney@sy*.ca*> Subject: O2 bends Maureen, Great to hear from you. Yes, I am ridiculously busy and will be travelling (work) a LOT this fall and throughout the winter. Oxygen bends are possible and have been observed in animals, BUT, to get them you have to dive the animal very deep on pure O2, explosively decompress them to the surface, and watch closely as they get bent and then quickly get better, without treatment of course. The rational is as follows. Hemoglobin is 97% saturated breathing air on the surface. Therefore, when diving the only increase in O2 delivery by the blood to the tissues is via dissolved O2. Every 100 mls of blood carries almost 20 mls of O2 attached to Hb and 0.3 mls disolved/pO2 of 100 mmHg. Therefore, at a pO2 of 1.6 ATA (the max diving and seldom actually reached), the blood is carrying 0.3 * 1.6 * 760 / 100 = 3.6 mls O2 dissolved. This slight increase in O2 being delivered to the tissues raises tissue pO2 slightly but as soon as the pO2 in the breathing gas drops, the pO2 in the tissues drops as the O2 is rapidly metabolized. Therefore, getting sufficient O2 supersaturation to form bubbles is almost impossible and they do not last long even then. Bottom line, in any reasonable sort of human dive, O2 decompression stress or bends are impossible. Good question. It's been a very long time since I had to answer that one. Take care, David -----Original Message----- From: Maureen Lunney [mailto:melunney@sy*.ca*] Sent: Monday, September 24, 2001 3:19 PM To: David.Sawatzky@dc*.dn*.ca* Subject: (no subject) Hi Dave, Hope you are busy and doing well. I heard via the grapevine that you had all sorts of exciting things planned these days. I had a decompression question that I am sure you can answer. Why don't we hear about oxygen bends? Obviously at high P02's the hemoglobin is saturated and the dissolved oxygen reaches toxic levels, but why no bubbles during ascent? Does the body metabolize the O2 so fast that this is not a problem even if a bubble forms? Or is 02 not prone to form bubbles in solution? I have read my Guyton, and my Diving Physiology texts but no one seems to tackle this directly. Any thoughts? Thanks and take care, Maureen -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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