Morgan
International Hazard
Posts: 1694
Registered: 28-12-2010
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On the Importance of Breathing Fresh Air
Dead air space tidbits and an illustrative 15 minute mask test at the end.
The Death Mask
https://www.youtube.com/watch?v=hilPPJEwq6I&feature=yout...
Full-face snorkel masks raise safety concerns
https://www.youtube.com/watch?v=wrHMtLsF2js
The topic brought to mind how the giraffe might get around the problem of dead air space with a 2.3 meter trachea length.
Dead space and tidal volume of the giraffe compared with some other mammals
https://www.sciencedirect.com/science/article/pii/0034568778...
[Edited on 6-1-2020 by Morgan]
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Fery
International Hazard
Posts: 1018
Registered: 27-8-2019
Location: Czechoslovakia
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Full-face snorkel masks - yes it increases dead volume dramatically.
When you exhale air from your lungs, some small volume always stays in airways which is low on O2 and high on CO2 (dead volume). Then when you start
inhaling, this vitiated air enters lungs first and only then fresh air follows. So the air in lungs is always a mixture of fresh air and vitiated air
(the ratio depends on the dead volume and the volume of inhaled air). If you increase dead volume by adding full-face mask then the dead volume
increases significantly. This must be compensated by deepened breathing which is of course exhaustive. For elderly people who do not have so big
reserves for compensation it could be fatal.
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