They were exposed to C02 levels 10x higher than what you'd be exposed to even in a poorly ventilated conference room. It's likely that this mitigates any biological differences.
Nothing is certain, but that study combined with the fact that submariners have been operating for months at at time with C02 levels up to 5,000ppm and no one has ever noticed a problem says that studies showing a severe impact at 1,500ppm are probably wrong.
Well, what was the 02 concentration? Did they just change the CO2 and N2 relative concentrations while keeping the O2 normal?
Not that I have detailed knowledge the implications of N2 vs CO2 on O2 uptake.
I could be wrong, but I would think the CO2 increase comes at an O2 loss. While there is about 20% of O2 in the atmosphere, and <1% CO2, but it only takes .2% of O2 --> CO2 to drop the relative concentration of oxygen by 1 percent, which should be noticeable, especially the more out of shape you are.
Naval seamen are also in a lot better shape, so they aren't on the borderline of O2 uptake (like a lot of the most vulnerable COVID-19 people).
The effects people are worried about are at 1k to 2k ppm. Even assuming CO2 is displacing O2 only, the drop in O2 levels is less than the change in about 100ft of elevation. Since oxygen only accounts for about 1/5 of the displaced gasses, you're talking about a difference in about 20 ft of elevation.
Not enough to notice even for horribly out of shape people, and definitely not enough to cause the kind of effects reported.
Have you been to Denver? Changing altitude has a greater than 1% change in O2 available. You feel it initially but quickly adapt and don’t tell them they are cognitively impaired. :)
It's not a good random sample, but they were exposed to C02 levels 10x higher than what you'd be exposed to even in a poorly ventilated conference room.
Possibly "tolerance" to high levels of CO2, and/or a baseline level of cognitive performance that's already impacted by chronic exposure to high levels of CO2?
Studies that raised the alarm on C02 levels showed a severe impact on cognitive function at 1,500ppm. Submariners routinely live and work in levels at 5,000ppm.
>baseline level of cognitive performance that's already impacted by chronic exposure to high levels of CO2
If that explanation is true submariners would barley be capable of operating their boats.
>Possibly "tolerance" to high levels of CO2,
And if that explanation is true new submariners would be barely functional.
The most likely explanation is that the study that showed severe impairment at relatively low levels is wrong.
I think the poster has a good point. It's not just the one submariner study he's referencing that's relevant, it's the decades of experience navies of various nations have operating submarine fleets - the armed forces are not shy about collecting physiological data in the service of operational readiness. If the headline article is correct, we should be very concerned that a significant fraction of the world's nuclear weapons are immediately operated by officers experiencing extraordinary CO2 exposure. Every submariner is green at some point (and there are female submariners as well) - how is acclimation handled?
I agree it's worth investigating. I just found it peculiar how unreceptive they were to the suggestion that the population was unrepresentative, yet how aware they were that the population was, in fact, unrepresentative.
The original suggestion, way up thread, was not to overgeneralize studies. This is a huge problem in our society.
I'm not unreceptive . It's entirely possible that fit militarily aged men under a certain height aren't as impacted by high C02 levels.
However I find it unlikely that they are completely immune to the effect at a dose 10x higher than what the people in the original Harvard study were exposed to.
As to whether long term exposure has a mitigating effect. That's possible, but if the effect is as great as the Harvard study shows, then the navy almost certainly would have noticed the impact on new submariners in the last 80 years.
Btw the original Harvard study was mostly college students, so it's hardly representative either.
All the studies I've seen that do show an impact, aren't using just C02, they are more broadly studying poor ventilation--C02 is just one factor. Every study that isolates C02 level shows nothing. The most likely explanation is that if there is an impact on cognition from poor building ventilation, it's not the C02 doing it.
I researched this topic pretty thoroughly a while back. I was worried enough by the hype that I bought a C02 monitor, but after I researched it, I'm not concerned.
These studies back up your claims. Thanks for sharing them. They were both done by the same people. Do you know if anyone else has tried to reproduce their results?
I would like to know the specific substances in exhalation that negatively affect humans. CO2 not being one of them would be good news.
>Those are prospective astronauts. I would expect them to be even more tolerant of CO2 and claustrophobia than submariners.
They weren't prospective astronauts, they were "astronaut like individuals". Men and women in their 30s and 40s with bachelor degrees and technical skills who can pass a modified flight physical (that from the description in the paper doesn't include any kind of C02 exposure).
Unlike submariners they aren't regularly exposed to 5,000ppm of C02, the height limit is much higher, and almost half of the participants were women.
They might be in better shape than the people in the Harvard experiment, because they screened out many medical conditions. But they are also lot older on average, and the exclusion criteria weren't particularly selective (140/90 bp for example).
Assuming good health has a protective effect you'd still expect so see some effect at 5x (5,000ppm) the level that showed an impact on the Harvard students.
The unrepresentativeness is irrelevant. It's quite conceivable that young fit men can take 20% more CO2 than the typical person before showing symptoms. 1000% is not, because it would have been noticed before and publicised as incredible. People have been on submarines for decades. You're telling me that, not only is there a hitherto unknown biological mechanism that renders young fit men practically immune to a toxic gas that debilitates the typical person at 0.1 times the dose and 0.01 times the exposure period, which is in itself a fantastic claim, but you're also telling me that this has not been noticed by any submariner in any country in decades! That nobody brought a fat politician aboard and noticed them keel over! That no old rich guy (perhaps... a famed movie director?) wanted to see the depths of the ocean! If you have priors on anything, it should be that this study is almost certainly wrong at a fundamental level. Quibbling about sample representativeness is a rounding error, which is why many people in this thread are well aware but completely uninterested in it.
> we were unable to replicate this effect in a submariner population
Please don't over-generalize paper results.