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Comments 301 to 325 out of 419:

301. Eric (skeptic) at 02:13 AM on 21 September, 2012
     DSL, ok, I see that now. Main conclusions  The current loss of mesic trees in the Sudano-Sahel zone appears to be driven by the sharp drop in rainfall since the 1960s, which has effectively stranded anthropogenically distributed species beyond their rainfall tolerance limits.
302. Philippe Chantreau at 02:55 AM on 21 September, 2012
     Well, I'm not entirely sure but the way I see it, AH1 argument is this: More atmospheric CO2 will lead to higher PaCO2 in circulating blood of live healthy animal subjects. This is a good thing because higher PaCO2 leads to reduced lymphocyte production of active oxygen forms and improved mitochondrial efficiency. The anesthesiology study on therapeutic hypercapnia applies to deperately ill patients on ventilators who are receiving what is called in medical jargon "heroic measures" so I consider it a stretch to apply that at any level to healthy subjects. In support of this theory, AH1 cites effects seen in high altitude acclimated subjects, under the assumption that these subjects experience higher than normal PaCO2 and that (it seems to be the argument) the higher PaCO2 is the reason for the beneficial changes. AH1 also asserts that people living at high altitude have better life expectancy. Let's examine the antioxidant part. It refers a number of studies by Kogan, Bolevich and Diliniak, with various others, that rely on chemoluminescence of lymphocytes. In this study it is found that the effect applies to healthy subjects but to only 30% of subjects with bronchial asthma, suggesting a possible decreasing sensitivity in subjects experiencing higher than normal PaCO2 due to the asthma. In this further study the same authors reach the following conclusion: "It may be held that the literature-described use of carbon dioxide for the treatment of bronchial asthma is justifiable only in a lower proportion of patients who have preserved a high sensitivity to the inhibitory effect of carbon dioxide on the generation of active oxygen forms." That's already not so encouraging, back in 1996. These studies are 16-17 years old and relied on chemoluminescence as an indication of lymphocyte activity. This articel, which predates the Kogan studies, shows some difficulties in interpreting CL results: http://www.ncbi.nlm.nih.gov/pubmed/7663293 Further investigation revealed that the changes in chemoluminescence observed were rather a consequence of the CO2 concentration itself than that of CO2 induced lymphocyte inhibition: http://www.ncbi.nlm.nih.gov/pubmed/12033328 I work with COPD and asthma patients quite often in a critical care setting. I have not heard of any form of hypercapnic therapy applied to these patients for the purpose of preventing free radicals formation. I looked at more recent reviews and did not see mention of hypercapnia. 17 years later, it does not appear that the line of research followed by Kogan, Bolevich and Diliniak was actively purseued by others. Permissive hypercapnia is normal in deperately ill ARDS patients because there are things taking much higher priority in these patients that bringing down the PaCO2, namely ensuring adequate oxygen delivery to the vital organs. Consideration on other claims to follow.
303. Bob Lacatena at 04:16 AM on 21 September, 2012
     Eric (skeptic), Of course the expansion is seasonal. That's the nature of the Hadley Cell (it migrates north and south of the equator with the sun). It can't, for the most part, expand only over the ocean and not over land. It doesn't work that way. And with the expansion, the arid areas must expand. This means Texas, Arizona, Oklahoma, Mediterranean Europe, and other places. There's no getting around this. The deserts will expand in places where human populations will be directly affected.
304. Philippe Chantreau at 04:37 AM on 21 September, 2012
     Let's take a look now at the high altitude claims. Those were put forth seemingly under the assumption that a high altitude environment presents conditions similar to what will be experienced in an atmosphere with more CO2. For myself, I consider the analogy inappropriate considering how significant the hypoxia is in the examples considered. Nonetheless, let's see what the science says. As I recall, AH1, you argued that high altitude induced a higher than normal PaCO2 to PaO2 ratio, which would be called respiratory acidosis. Educational texts on the subject disagree: http://jan.ucc.nau.edu/~pe/exs336web/336altitude.htm It is also contradicted by this study: http://www.ncbi.nlm.nih.gov/pubmed/9079156 Note that Sherpas do have a slightly higher PaCO2 than Caucasians, but at all altitudes. Note also: "Moreover, in Caucasians sojourning for 3 weeks at 5050 m, PaCO2 kept decreasing whereas pHa, PaO2 and SaO2 remained constant." In caucasian people, acclimatation to altitude led to a lower PaCO2. In fact, the study points to Sherpas having a higher PaCO2 purely as an adaptation to limit the respiratory alkalosis brought by all the other responses to hypoxia. I looked at the life expectancy of various countries and did not find evidence of an advantage to high altitude living: https://www.cia.gov/library/publications/the-world-factbook/rankorder/2102rank.html Nepal ranks #161, less than low lying countries without well developed health care, like Viet-Nam and many more. Modern advances have brought Sherpas' life expectancy to from 35 to 65. The islands of Sardinia and Okinawa have the highest rates of centenaries in the World. http://en.wikipedia.org/wiki/Sardinia The study on animal hearts cited earlier was given a somewhat selective quote. This study points to cattle heart adaptation to hypoxic conditions and says nothing about CO2. Here is the end of the abstract: "These changes are discussed as an intracellular mechanism which would serve to preserve oxidative metabolism in hypoxia, particularly under exercising conditions. The effective conservation of oxygen pressure head by this means is probably less than one mm Hg." The hypoxic conditions endured by these animals are severe enough to trigger a massive adaptation of the heart, whose sole purpose is to ensure adequate oxidative capability. No doubt that, put at sea levels, these would be some pretty darn athletic cows, at least for a little while, until they adapt to the new conditions. High altitude athletic preparation is well known and practiced because it enhances oxygen transport and oxygen use, not because it raises CO2. It is also well known that the benefits of high altitude preparation fade away pretty quickly when the body lives again at normal altitude. I cited a study discussing the ventilatory response to CO2 and was told that the point was missed. The point is that the brain stem centers that regulate ventilation have sensors that are extremely sensitive to CO2. The moment PaCO2 increases, ventilation kicks in to re-establish normal range. In other words, healthy people will not all of a sudden start to live with a higher PaCo2, altitude or not, higher amospheric CO2 or not. In summary: The claim that high altitude leads to higher PaCO2 is not verified in scientific litterature or physiology texts. Sherpas have higher PaCO2 at all altitudes. Their life expectancy is mediocre by world standards. Response to altitude related hypoxia actually reduces PaCO2. The claim that people living at high altitude live longer has no merit; it is not verified by worldwide demographics. Nepal ranks #161, Bhutan is #158. The top 10 include Monaco, Macau, Hong-Kong, Singapore and Gernsey, where people live pretty much at sea level. In japan (#1) the immense majority of the population resides in the low lying cities. I see no evidence of any altitude related PaCO2 effect on mitochondrial population and efficiency. What was presented instead is evidence of mitochondrial response to hypoxia. Although it was kinda fun to look up, I'm not sure I'm going to continue spend time on this.
     Response: [Sph] And that is how one presents a scientific argument and supports it with citations/references, rather than mere declarations of confident knowledgehood.
305. anon1234 at 04:46 AM on 21 September, 2012
     doug_bostrom, you said, "You refuse to specify the benefits you anticipate from additional C02 in the atmosphere." OK, let me clarify a bit. Benefits depend on the rate of increased atmospheric Co2. A very slow, steady build up in Co2 levels would be ideal (allowing for organisms to properly adapt- it would be horrible if Co2 went from 400 ppm to 10,000 ppm overnight, we would all be dealing with hypercapnia as in altitude sickness) within a certain limit. The benefits, after adaptation has taken place (and metabolism is boosted depending on the degree of hypercarbia) are the benefits associated with higher altitude dwellers (because organisms adapting to the higher internal Co2 to O2 ratios of high altitudes are a perfect case study the effects of hypercarbic adaptaion, as I have pointed out). Namely, reduced mortality rates, reduced level of injury (due to the mild respiratory acidosis), and increased metabolic efficiency. Dikran Marsupial, but adaptation to high altitudes does provide a perfect illustration of higher internal Co2 to O2 ratios. Altitude sickness is an adaptive response to hypercapnia. The effects which high altitudes exhibit on adapted dwellers (higher metabolism, lower mortality rates, etc.) is what one would expect from higher exposure to Co2, through the mechanisms I have described (antioxidant, promoter of krebs cycle activity). Sphaerica, on 1. I agree with this statement (again, controlled studies, describing specific mechanisms are required to make the claim). on 2. The use of absolutes renders this statement obviously false. on 3. My argument is not one of ultimate value (in the sense of making a judgement on the overall "goodness" or "badness" of anthropogenic atmospheric Co2); this is the strawman that I identified earlier. 4. I have not made this judgement, because it encompasses literally millions of other factors, and value judgements. I am just pointing out that the benefits that Co2 exhibits on organisms should be included in the cost-benefit analysis. Do you disagree? If so, why? Eric and DSL, I think my point has been misinterpreted a bit, but would you mind if we continue hashing out desertification on the other thread? This one is already quite long and is pretty all encompassing. When we come to some conclusions over there, the issue can be more easily incorporated into this thread. thanks,
306. Philippe Chantreau at 04:56 AM on 21 September, 2012
     Oh what the heck since we're at it. Here is an interesting study on long term changes of plant mitochondrial metabolism in elevated CO2 environment. http://www.plantphysiol.org/content/145/1/49.full.pdf Quote from the end of the abstract: "However, despite growth enhancement and as a result of the inhibition in cytochrome pathway activity by elevated CO2, total mitochondrial ATP production was decreased by plant growth at elevated CO2 when compared to ambient-grown plants. Because plant growth at elevated CO2 increased biomass but reduced respiratory machinery, activity, and ATP yields while maintaining O2 consumption rates per unit of mitochondria, we suggest that acclimation to elevated CO2 results from physiological adjustment of respiration to tissue ATP demand, which may not be entirely driven by nitrogen metabolism as previously suggested."
307. Philippe Chantreau at 05:27 AM on 21 September, 2012
     "we would all be dealing with hypercapnia as in altitude sickness." Funny, earlier hypercapnia was proposed as a good thing. I guess perhaps you mean to make a dosage dependent distinction. Nonetheless, this is what better sources say on altitude sickness: http://wiki.medpedia.com/Altitude_Sickness Quote: "Although treatable to some extent by the administration of oxygen, most of the symptoms do not appear to be caused by low oxygen, but rather by the low CO2 levels causing a rise in blood pH, alkalosis." Altitude sickness hypercapnia eh? right. I'm sorry AH1, you're full of it. I'm done here.
308. anon1234 at 06:53 AM on 21 September, 2012
     Wow.. I missed this whole page when commenting earlier. Thanks for attacking the information! I really enjoy a good dialogue. Philippe Chantreau, I said high altitude natives have lower general mortality rates, not increased longevity. you said regarding Co2's antioxidant activity, "Further investigation revealed that the changes in chemoluminescence observed were rather a consequence of the CO2 concentration itself than that of CO2 induced lymphocyte inhibition: http://www.ncbi.nlm.nih.gov/pubmed/12033328" This is a very interesting study! But if you'll notice, it claims that CO2 can enhance chemiluminescence (a sign of oxidative damage [ http://www.sciencedirect.com/science/article/pii/0003986179901024 ]). Studies using chemiluminescence as a factor in determining the antioxidant nature of a substance would show a decreasing rate of chemiluminescence- because it is associated with lipid peroxidation. Furthermore, when you mention "In this study it is found that the effect applies to healthy subjects but to only 30% of subjects with bronchial asthma." you bring up in vivo evidence that supports CO2's role as an antioxidant. The fact that there is a threshold to its protective action is only reasonable. People with COPD or severe asthma already are exposed to higher internal CO2 to O2 ratios. The fact that there is an antioxidant benefit in 30% of asthmatics who participated in this study helps my argument. this study, http://www.ncbi.nlm.nih.gov/pubmed/9079156 , which you posted is interesting. It could disprove a (minor sub-)theory that I presented regarding the mechanism of mild respiratory acidosis reducing organ damage and thus mortality rates. I would think that the more extreme elevation a person is at (everest like), the more alkaline they would be in general (because of a respiratory response to reduced internal O2 levels). But people who are heavily acclimated to any higher elevation will be more acidic than people actively adapting to said elevation. Your study shows this to be true. People acclimated to 6000 ft above sea level would be more acidic in general than Sherpas on Everest. It also shows that the life-long acclimation to hypoxia of the sherpa makes him slightly more acidic (because of increased PaCo2 levels), through depression of respiration. I would expect white boys climbing everest to be hyperventilating like crazy and thus induce respiratory alkalosis. Remember that the rate of ventilation is the major immediate adaptive response to hypercapnia and high altitudes, which is depressed in those heavily acclimated (like the sherpas). you said, "Altitude sickness hypercapnia eh?" Yes, which will cause an immediate urge to hyperventilate changing respiratory acidosis into alkalosis- changing hypercapnia into hypocapnia. you said, "I looked at the life expectancy of various countries and did not find evidence of an advantage to high altitude living:" Oh yea, I'm sure you took all the other potential factors into account as well (such as rates of smoking, drinking, self-flaggelation, empty calorie consumption, intake levels of and quality of fat, average caloric intake, STDs, the fact that many countries vary wildly in internal altitude etc.) you said, "The claim that high altitude leads to higher PaCO2 is not verified in scientific litterature or physiology texts. Sherpas have higher PaCO2 at all altitudes." What?- doesn't this study show that those highly adapted to high altitudes (Sherpas) DO have increased PaCO2, and are more acidic than those who have not adapted as much? What do you think of the cow heart studies I mentioned (as opposed to the plant one you mentioned), which show elevated mitochondrial density in cows adapted to higher elevations (lower internal O2 supply in relation to CO2)?
309. anon1234 at 06:57 AM on 21 September, 2012
     **Edit # 308- cow heart studies should read, "cow heart study" thanks
310. Bob Lacatena at 07:13 AM on 21 September, 2012
     305, AHuntington1,

     I am just pointing out that the benefits that Co2 exhibits on organisms should be included in the cost-benefit analysis. Do you disagree? If so, why?

     First short answer: You haven't established benefits that CO2 exhibits on organisms, you've merely claimed them. Second short answer: Because I live in the real world, where imagined minor benefits do not outweigh proven major drawbacks. Beyond this, it is silly to make the presumption that increased CO2 will be beneficial to all species equally. In fact, try reading this article. Bottom line: I find your point to be both worthless and misleading. It adds nothing to the discussion. It's like being given a cyanide capsule and being told "look on the bright side, it tastes like almonds!"
311. anon1234 at 09:36 AM on 21 September, 2012
     Sphaerica, you said, "You haven't established benefits that CO2 exhibits on organisms, you've merely claimed them." Well, way to ignore all of the evidence I have supplied so far. Please address my info, or stop posting. you also said, "Because I live in the real world, where imagined minor benefits do not outweigh proven major drawbacks." You are still attacking the same strawman... you say, "it is silly to make the presumption that increased CO2 will be beneficial to all species equally. In fact, try reading this article." Ok, well here's a new strawman, at least. Where did I ever say that elevated CO2 would be beneficial to all species equally? Where are you getting this from, if you don't mind me asking? Bottom line: consistently attacking strawmen and using red herrings does not make a point, nor even come close to proving me wrong. Implying that I do not live in the "real world" and that I am "imagining" things, drawing up bogus comparisons between CO2 and cyanide, using red herringss to distract from my point- these things are not acceptable in a scientific discussion and some of them border on ad hominem attacks. I will not engage in a discussion with you until you display the ability to carry on a respectable, scientific dialogue.
312. Doug Bostrom at 10:02 AM on 21 September, 2012
     Let's rinse and repeat, ahuntington1, since we've been through the citation mill again and still have not heard any specific claims useful for evaluating whether metabolic benefits of increased atmospheric C02 concentration might be worth attendant risks. Can you describe specifically how one's day might be so much better breathing an atmosphere with a higher C02 concentration? What would a subject notice? What would be the impact on mortality and susceptibility to adverse health experiences? What's the payoff outside of a test tube? If you can show in concrete terms how the population stands to benefit from increased C02 respiration, how likely are the specific benefits you've shown? Certain? Sometimes? Almost never? What's the risk/benefit equation here? Be specific. For instance, for a person living in Dhaka, Bangladesh is the payoff worth it?
313. anon1234 at 10:55 AM on 21 September, 2012
     doug_bostrom, what attendant risks are you referring to? For humans to be negatively affected by atmospheric CO2 it would have to be over 4% (which is when deleterious effects begin occurring, if I remember correctly). Increasing atmospheric CO2 from 400 ppm to 10,000 ppm overnight would have negative health effects, but this is not very realistic. you asked, "What's the risk/benefit equation here? Be specific. For instance, for a person living in Dhaka, Bangladesh is the payoff worth it?" I have no idea- again it has to do with many other factors. Eg. if someone is starving or dehydrating increased CO2 would probably not be very effective.
314. Doug Bostrom at 11:02 AM on 21 September, 2012
     Ahuntingdon1, you're declaring bankruptcy for your premise. You know that, right?
315. Bob Lacatena at 11:10 AM on 21 September, 2012
     AHuntington1, 1) You have not supplied a single citation which proves your point. 2) It is a "strawman" only because you refuse to address the point. A positive which is outweighed by the negatives is of no value. It is a simple reality. The fact that you want to ignore that reality does not make it a strawman, it makes it an argument you want to avoid because it's one you can't win. Let me state it more clearly, then: Your point that CO2 will provide the benefit of improving mitochondrial respiration, true or false, is irrelevant because it ignores the other greater, negative impacts associated with CO2.
316. anon1234 at 12:23 PM on 21 September, 2012
     doug_bostrom, um, would you please be a little more specific? Again, I have no idea what you are referring to (nor should I be expected to read your mind). thanks, Sphaerica, (-snip-). (-snip-)
     Response: [DB] Inflammatory and sloganeering snipped. Please ensure all comments comply with the comments policy before posting further.
317. Bernard J. at 13:56 PM on 21 September, 2012

     Oh yea, I'm sure you took all the other potential factors into account as well (such as rates of smoking, drinking, self-flaggelation, empty calorie consumption, intake levels of and quality of fat, average caloric intake, STDs, the fact that many countries vary wildly in internal altitude etc.)

     Oh, the irony...
318. Bob Lacatena at 14:13 PM on 21 September, 2012
     AHuntington1, I'll make it easy for you. 1. My statement is that your statement about mitochondrial respiration is irrelevant, because the negative impacts of temperature and water availability will vastly outweigh any possible positive influence on mitochondrial respiration. 2. There is no actual evidence that increases in atmospheric CO2 will result in improved health for any fauna through improved mitochondrial respiration. If you are in opposition to either of these statements, you are asked to supply specific references that clearly support your position. You are also asked to paste in the quotes of any segments from the conclusions which support your position (simply providing links to papers and claiming that they support your position will not be adequate, because it leaves you with too much latitude to simply fudge it).
319. Philippe Chantreau at 14:57 PM on 21 September, 2012
     How weak of me to be suckered in to this again. For my defense, I have to say that AH1's stuff is really funny in a way. For the sake of the sincere reader examining this thread, here is some more: AH1 gives every indication that he searches the web with the purpose of finding every little bit that could be used to say "CO2 is good for us." In the course of doing so he finds stuff that he does not really understand and makes bold assertions that he later amends by trying to imply that he meant something different. We had this on post#250: "neither aerobic nor anaerobic bacteria can survive without Co2 highlights this fact." With a link to paper that does not exactly say what AH1 says it says. From the abstract: "the observation that relatively low concentrations of CO2 were adequate for satisfactory growth of certain anaerobes was of particular interest." Walker and Winslow showed as early as 1932 the ability of E.Coli to grow in the absence of CO2 on a medium more complex than the very basic one. That's obviously not the kind of depth where AH1 will go. Whatever. Then we get this: "High altitudes provide a real life example of a population that breathes a higher Co2 to O2 ratio", in the same post. When corrected on this, AH1 amended himself by saying that it was a "mis-type", and what he meant was that people living at high altitude have a higher "internal" CO2 to O2 ratio. I had to introduce the concepts of PaCO2 and PaO2, which are very familiar to those of us who really work with this and really save the lives of people in respiratory failure. He showed no evidence of that supposed imbalance. Instead he cites this article: http://jap.physiology.org/content/16/3/431 The article says nothing at all about PaCO2 to PaO2 ratio but only reinforces the well known higher ability of high altitude residents to transport and use oxygen: "The higher O2 consumption per kilogram of FFM, C, or S in the high-altitude resident seems to be one of the many mechanisms developed by the body in its process of adaptation to the low O2 tension." I will add that, from a purely physiological point of view, CO2 elimination should be easier at high altitude. The body processes are unchanged and the PaCO2 resulting from metabolism remains about the same, but the absolute pressure of CO2 in the ambient air is much lower at high altitude, thereby facilitating CO2 elimination in the lungs. The published litterature suggests that high altitude dwellers are in fact in a steady state normal acid-base balance adapted to the lower pressure of CO2, exactly as one should expect from regulatory mechanisms: http://www.ncbi.nlm.nih.gov/pmc/articles/P(1)MC3068777/ I note that this paper represents a change from the previous dominant idea, which was one of chronic alkalosis. I showed a study looking at Sherpas that found a slightly higher PaCO2 than other people. AH! AH1 jumped on it with the belief that it proved his point but he missed that part: "(1) respiratory alkalosis was a common finding both in Caucasians and Sherpas." He also seemed to have missed this part: "Apparently a more efficient adaptation to hypoxia allows Sherpas to limit alkalosis through a lower ventilatory drive and to maintain SaO2 at the same PaO2 by decreasing the [2,3-DPG]/[Hb] ratio." Sherpas limit alkalosis by a more efficient response to hypoxia but still experience it. I'll note that Sherpas seem to be unique in this ability; that points to a genetic difference that has not surfaced in other people living at high altitude like those in the Andes. The point is: there is no PaCO2 to PaO2 imbalance in high altitude dwellers. Alkalosis is the initial response and an incidental cause of the reaction to hypoxia. Balance is restored with aclimation. Alkalosis is seen in higher altitude excursions even in highly adapted dwellers. The alkalosis is brought by responses to hypoxia, not hypercapnia. AH1 tries to wiggle out of his gross error on altitude sickness by trying to imply that the sickness is due to alkalosis as an overreaction to hypercapnia and that is what would happen to people exposed to suddenly increased high levels of CO2 at normal pressure. Total nonsense. If one was suddenly exposed to high levels of CO2 at normal pressure, ventilation would increase in order to restore normal PaCO2, then would stabilize as that goal would be reached and alkalosis would not develop. In altitude sickness, hyperventilation persists despite alkalosis because of hypoxemia, leading to further alkalosis. The vascular changes associated with low Co2 and low O2 are currently believed to be the most likley causes of vessel permeability leading to pulmonary edema and cerebral edema. AH1 made an argument about people's death rates at high altitude. I took the bait and looked at life expectancy, which of course did not support his argument. Then he went on to remind us of the distinction in terms and listed all sorts of factors that are more likely to affect mortality rates than life expectancy. Right. Makes sense. It is difficult to devise a good metric for population health. Despite controversy, according to numerous demographics textbooks and the E.U. demographics department, one of the best, if not the best, indicators of population health is the expected number of years without disability or disease: healthy life expectancy. Its detractors have yet to come up with a better one. Let's see how that pans out. This paper has plenty of details, methods, etc, and nifty graphics on healthy life expectancy: http://www.who.int/healthinfo/paper38.pdf No evidence of special benefit to high altitude locales. Easier to look at: healthy life expectancy ranking http://www.photius.com/rankings/healthy_life_table2.html Conclusion: AH1 makes all sorts of claims for which he has no evidence, cites papers as evidence of assertions of his that the papers in fact do not support, misunderstands his own cites and that of others, selects quotes in his and others' citations, makes sweeping statements not supported by any evidence existing out there, adjusts his language when he's caught spewing nonsense. Impressive. This time I'm really done. I'd advise all to resist temptation better than me and NFTT.
320. Philippe Chantreau at 15:03 PM on 21 September, 2012
     And mods, feel free to snip whatever content above you find inflammatory, as the substance will be unchanged.
321. Philippe Chantreau at 18:39 PM on 21 September, 2012
     Last detail: "incidental cause" above should be "incidental consequence."
322. gws at 18:59 PM on 21 September, 2012
     one more thing AH1 (@313) is off by a factor of ten regarding harmful CO2 levels: "In summary, OSHA, NIOSH, and ACGIH occupational exposure standards are 0.5% CO2 (5,000 ppm) averaged over a 40 hour week, 0.3% (3,000 ppm) average for a short-term (15 minute) exposure [...], and 4% (40,000 ppm) as the maximum instantaneous limit considered immediately dangerous to life and health. All three of these exposure limit conditions must be satisfied, always and together." available here
323. Dikran Marsupial at 19:17 PM on 21 September, 2012
     AHuntington1 wrote: "Dikran Marsupial, but adaptation to high altitudes does provide a perfect illustration of higher internal Co2 to O2 ratios." You are missing the point. How do you know that the effect is due to the difference in CO2 to O2 ratio rather than to other changes in body chemistry due to lower atmospheric pressure and lower oxygen availability. How do you know that the same effect will also be seen at sea level pressure with the concentration of O2 to which we are evolutionarily adapted? Now I suspect that if this were the case, then competent scientists would have performed the experiment to find out (e.g. monitor glucose metabolism in a sealed environment in lab conditions where all other factors can be controlled). The fact that you can't supply a single study where this has been done suggests to me that the scientists who work on this don't suspect that mechanism has a significant effect. So please answer this question directly and unambiguously: Is there anyone other than yourself that is promoting this hypothesis, yes or no?
324. Philippe Chantreau at 03:29 AM on 22 September, 2012
     Dikran, there is no PaCo2 to PaO2 imbalance. It's rather the opposite. The article by Dr Zubieta-Calleja I cited above has the complete discussion. BTW, the address was damaged, this is the real link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3068777/?tool=pmcentrez The tutorial on altitude sickness I cited earlier is also very clear. Hypercapnia is not involved. Hypoxia is the primary cause of hyperventilation that persists to and beyond alkalosis. AH1 has no clue what he's talking about, he really should be ignored.
325. anon1234 at 04:49 AM on 22 September, 2012
     Philippe Chantreau, you said, "Walker and Winslow showed as early as 1932 the ability of E.Coli to grow in the absence of CO2 on a medium more complex than the very basic one. That's obviously not the kind of depth where AH1 will go. Whatever." Whatever, indeed. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2065164/pdf/brjexppathol00219-0137.pdf Please cite the article (and medium for that matter) you are referring to. you said, "I had to introduce the concepts of PaCO2 and PaO2 [...]" When I have introduced biological concepts on this thread, I have had to repeatedly describe them in great detail (when wikipedia is available). I didn't want to make extra work for myself by introducing PaCO2. Internal CO2 to O2 ratios are a simple way to describe PaCO2 to PaO2. I am very glad that you wield knowledge of biology, and are willing to criticize my information- thank you, btw. you said, "from a purely physiological point of view, CO2 elimination should be easier at high altitude." Of course it is, this is why adapted organisms have a reduced rate of respiration, thus having higher PaCo2 (and be slightly more acidic) than someone actively adapting. sou said, "If one was suddenly exposed to high levels of CO2 at normal pressure, ventilation would increase in order to restore normal PaCO2, then would stabilize as that goal would be reached and alkalosis would not develop." You are absolutely right. I concede this point, although atmospheric CO2 increasing as a result of burning (of fossil fuels or trees and grass) would cause a reduction in concentration of O2, all else being equal. Reduced atmospheric O2 pressure is a large potential effect of widespread human fires. you said, "I note that this paper represents a change from the previous dominant idea, which was one of chronic alkalosis." Thanks for fixing the link! It is an interesting paper which does change the previous (or current depending on who you ask)dominant theory as to acid/base imbalances at altitude. I am skeptical, though, because the mechanism for lower atmospheric O2 pressure causing alkalosis in Sherpas makes sense. you said, "AH1 made an argument about people's death rates at high altitude. I took the bait and looked at life expectancy," Well you took bait that I didn't provide. I did say mortality rates (as did the wikipedia, and study I posted). you said, "The vascular changes associated with low Co2 and low O2 are currently believed to be the most likley causes of vessel permeability leading to pulmonary edema and cerebral edema" This is an interesting theory, but mortality rates from cardiovascular disease are significantly lower in people adapted to low pressure (whats a bigger problem, edema or heart disease?). this study http://circ.ahajournals.org/content/120/6/495.full (which I have already posted), shows significantly decreased mortality rates for people with cardiovascular diseases who are exposed and adapted to the low pressure of high altitudes (reduced respiratory rate, increased PaCO2 in relation to a steady PaO2 or higher internal CO2/O2 ratio). you said, "Sherpas limit alkalosis by a more efficient response to hypoxia but still experience it." Of course they do; to quote myself, in post #308 "the more extreme elevation a person is at (everest like), the more alkaline they would be in general (because of a respiratory response to reduced internal O2 levels)" you said, "Dikran, there is no PaCo2 to PaO2 imbalance. " Adaptation to lower pressure increases PaCO2- PaO2 is relatively stable at all altitudes. I am glad that you seem to accept (or at least not reject) the evidence I have presented regarding CO2's antioxidant activity. and again, thank you for addressing the points that I did make, I sincerely appreciate it. gws, thank you for pointing that out (perhaps this is what doug was on about), that totally should have read ~ 0.4% (or ~ 4000 ppm). Remember that 4000 ppm is a tenfold increase in current atmospheric levels. Dikran Marsupial, you said, "You are missing the point. How do you know that the effect is due to the difference in CO2 to O2 ratio rather than to other changes in body chemistry due to lower atmospheric pressure and lower oxygen availability. " Thanks for clearly making the point; The effects of adaptation to high altitudes (increased metabolic rate etc.) are consistent with what one would expect from increased exposure to CO2 (because of its antioxidant activity, and its role in protecting and properly distributing the body's O2 supply) which is one result of adaptation.

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