SCOTT SIMON, host:
An interesting study appeared this week in the New England Journal of Medicine about oxygen levels in blood. The experiment took place above 27,000 feet up on Mount Everest. Four mountaineering physicians unzipped their down suits and exposed their groins, all for the sake of science. They extracted samples of their own blood at freezing temperatures to measure the effects of altitude on blood oxygen levels. Dr. Mike Grocott headed the team. He joins us from Southampton, England. Doctor, I've got to ask. I mean, they've got high altitude chambers these days. Why did you have to go up to Mount Everest to take a blood sample from your groin?
Dr. MIKE GROCOTT (Co-director, Center for Aviation, Space, and Extreme Environment Medicine, University College London): There have been previous studies taking these sort of measurements in chambers. Interestingly, the results have - are different. They're not as low. And that may be because climbers, because they're exercising quite heavily for a long period of time, actually develop some fluid in their lungs.
SIMON: And why not just take the blood sample from your fingertip?
Dr. GROCOTT: In order to know what the heart and lungs are sending out to the tissues, you need to take the sample from an artery. And you can find them in various places. So the place we classically think of is in the wrist. Unfortunately, when it's relatively cold, those arteries tend to constrict down. They become very small and very hard to get a needle in.
SIMON: So how cold was it?
Dr. GROCOTT: It was probably a little bit over freezing. But that was because we descended from the summit, and we were in a small shelter. We originally had planned to take the blood on the summit, but it was about minus 25 there with 20 knots of wind.
SIMON: So what did it feel like?
Dr. GROCOTT: I guess it felt slightly strange. Certainly, the climbers around us thought it was slightly strange that we were pausing to take blood samples from our groin.
SIMON: (Laughing) Yeah, I mean that's not recommended mountaineering technique, is it, to get up at that altitude and drop trou?
Dr. GROCOTT: It's unusual.
SIMON: Well, let's hope.
Dr. GROCOTT: (Laughing) Yeah.
SIMON: And what did you learn?
Dr. GROCOTT: Firstly, the values that we found are extraordinary low. It's amazing that we were able to function effectively given those low numbers. And that maybe alters a little bit our understanding of what - given sufficient time and the time factor, the fact that we'd had a period of time to acclimatize - but given sufficient time, it is extraordinary how much humans can adapt. And there may be implications that lead from that to the care of patients.
The reason I say that is because when patients become critically ill, we use high levels of oxygen and mechanical ventilation to maintain a level of oxygen in the blood. Now, sometimes using the supplemental oxygen used in ventilation can itself be causing harm. And what we speculate is that it may be that if we aimed for a slightly lower target in some patients who've had a duration of time to adapt to the low oxygen level, we may be able to do less of these potentially harmful interventions, and thereby overall the patient benefits.
SIMON: Well, Dr. Grocott, good climbing to you in the future, sir.
Dr. GROCOTT: (Laughing) That's very kind. Thank you. Bye-bye.
SIMON: Dr. Mike Grocott. He's co-director of the Center for Aviation, Space and Extreme Environment Medicine at University College London. This is NPR News.