From the study, emphasis mine:
> we were unable to replicate this effect in a submariner population
Please don't over-generalize paper results.
> we were unable to replicate this effect in a submariner population
Please don't over-generalize paper results.
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.
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 general population is much more out of shape.
Not enough to notice even for horribly out of shape people, and definitely not enough to cause the kind of effects reported.
It's not exactly a good random sampling, they filter candidates very aggressively.
>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.
People are telling you that this study may not be reflective of the general population, and you are only demonstrating their point.
It seems like you are really invested in a particular outcome for this research. Maybe you should take a step back and try to let go of your biases.
Dying on the hill of one particular study is the definition of cherrypicking.
The original suggestion, way up thread, was not to overgeneralize studies. This is a huge problem in our society.
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.
Here's another study that shows no impact on military aged people who aren't submariners https://www.ncbi.nlm.nih.gov/pubmed/31240239.
And here's a study that showed no impact from an introduction of pure C02 (these weren't submariners either) https://onlinelibrary.wiley.com/doi/full/10.1111/ina.12284?c...
And here's another one that shows no cognitive impact at 5,000ppm https://www.sciencedirect.com/science/article/abs/pii/S03601...
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.
Those are prospective astronauts. I would expect them to be even more tolerant of CO2 and claustrophobia than submariners.
> And here's a study that showed no impact from an introduction of pure C02 (these weren't submariners either) https://onlinelibrary.wiley.com/doi/full/10.1111/ina.12284?c....
> And here's another one that shows no cognitive impact at 5,000ppm https://www.sciencedirect.com/science/article/abs/pii/S03601....
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.
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.
Is a submarine’s ratio of O2 to CO2 maintained at a normal fresh air ratio at its higher absolute CO2 level?
etc.