The Hacker News discussion revolves around a record for holding one's breath underwater, particularly after breathing pure oxygen. Several key themes emerge:
Spleen Capacity and Physiology
A significant portion of the discussion focuses on the role and size of the spleen, particularly in relation to freediving and breath-holding. The Bajau people, known for their free-diving abilities, are mentioned as having enlarged spleens which act as a reservoir for oxygenated blood.
- The initial comment directly links the record to the spleen: "His spleen must be enormous[1]."
- Users also highlight the physical risks associated with an enlarged spleen: "And he should avoid high impact sports and never get into a motorcycle accident. Spleens are big bags of blood, and trauma to them, especially when enlarged or inflamed, can be fatal. It's one of the easiest accidental ways to bleed out."
- A more speculative point is raised about potential genetic predispositions: "I wonder if their babies also have enlarged spleens."
- Another user brings up a curious biological possibility: "And injury to it can cause spleen cells to colonize other parts of the abdomen. You could end up with extra spleens!"
The Impact of Pure Oxygen
There's a detailed exploration of why breathing pure oxygen significantly extends breath-holding time, as well as the implications and potential dangers of oxygen toxicity at different pressures.
- The crucial difference in breath-holding duration is noted: "That's 29min 4sec after breathing pure oxygen." and "The record for regular air is 11min 35sec."
- Users discuss the mechanism by which pure oxygen aids breath-holding: "Note this is oxygen assisted - the diver breathed pure oxygen and (from the article) can increase available oxygen from 450mL to 3L in doing so."
- The concept of oxygen toxicity and its relation to pressure is a major point of conversation: "I somehow thought that pure oxygen was poisonous[1], and it needed to be a nitrogen mix. I mean, I guess this stunt demonstrates that I'm clearly mistaken, or that the nuance is in the pressures involed?"
- One user explains: "It's dangerous in an enclosed environment, see Apollo 1 for more details." and another clarifies: "Pure oxygen puts oxidative stress on your cells. Your body can handle that just fine at 1 atm, but at elevated partial pressures the increased concentration will (quickly) overwhelm your cellular mechanics."
- The critical factor of partial pressure is emphasized: "Yes. It’s under pressure that oxygen toxicity becomes an issue. It’s why you’ve gotta pay attention to your depth when diving with enriched air." and "Yes, partial pressure is what matters. Normal air at 1 bar (1 atmosphere) contains about 0.2 bar of O2. Pure oxygen at sea level is 1 bar of O2."
- A detailed explanation from a user touches upon tolerance limits: "The article you linked has a graph showing that 0.5 bar of O2 can be tolerated pretty much indefinitely, and it takes hours for significant toxicity to show up at 1 bar. Higher partial pressures cause much faster symptoms." and "This means you could breath 80/20 nitrox at 2.5 bar, or 37 psi, or 25 meters depth, "indefinitely" in the sense of hours or days."
- The difference between short-term use at 1 atm and long-term or high-pressure use is highlighted: "At 1 atm you need to be breathing pure o2 for ~24 hrs before its meaningful... The dose isn't even cumulative. Just being on room air for 20-30 minutes resets the clock." and "PS: Chronic use of 100% oxygen at atmospheric pressure causes other types of toxicity."
The Dangers of Breath-Holding and Training
Several comments address the inherent risks associated with breath-holding techniques, particularly concerning shallow-water blackout and the body's warning systems.
- A direct warning about a common, dangerous practice is given: "Many kids will grasp the obvious trick of hyperventilating to improve their time, but that can lead to abrupt unconsciousness and drowning."
- The reliance on CO2 as a warning sign is explained: "The funny thing is the co2 isn't doing much in the short term except make you feel completely terrible, because that's how most mammals evolved not dying in caves and underground tunnels. You can't feel low o2 (well, you can with training like aviators get) so you feel excess co2 instead."
- The lack of explicit safety details in the article is a concern for one user: "Coming back to the article, I'm disappointed that the details were sparse - how do they check whether the contestant is conscious? How does the contestant know what his limits are before passing out?"
- The perceived underestimation of danger is noted: "I'm surprised they don't make any mention of how dangerous this sport can be. Particularly if you are taking steps to avoid CO2 build-up, which is the thing that that triggers the suffocation reflex."
User Experiences and Training Regimens
The discussion includes personal anecdotes and observations about learning to hold one's breath, with varying levels of success and personal strategies.
- Some users recall childhood attempts: "When I was a kid in the 70s, I think the record was somewhere in the neighborhood of 3–5 minutes... and we used to think that was such a short time that we could do it and then trying in the backyard bucket pools... found that cracking a minute was enough of a challenge."
- Another user describes a similar experience of improvement: "At first, yeah a minute was tough. But then it rapidly increased. Unfortunately I don't remember where we topped out, but I think ~3 minutes."
- Specific training techniques are mentioned, including the Wim Hof method: "I increased my lung capacity using Wim Hof breathing technique and can now hold my breath for 3 minutes."
- There's a comment about the perceived ease of achieving basic breath-holding times: "Most people on this forum could hit 3 minutes with normal air in an afternoon of training."
- A user inquires about other potential enhancements: "I wonder if the diver used any assistance to improve their oxygen capacity? Adding extra red blood cells into our body? Increasing the oxygen capacity of existing cells? Is there anything we can eat/drink that would soak up excess carbon dioxide?"
Broader Context and Cultural References
The discussion touches upon the cultural perception of freediving, its portrayal in media, and its historical context.
- The role of movies in popularizing freediving is acknowledged: "Free diving wouldn't be mainstream conscientiousness if it wasn't for possibly one of the greatest movies of all time"
- A comparison is made to a famous performer's feat: "It’s a classic at this point but David Blaine held the record for a while and gave a fantastic TED talk on his process"
- The mammalian diving reflex is identified as a contributing factor: "Another factor is that it's easier to do it underwater than on land. The mammalian diving reflex is what helps."
- A lighthearted, albeit geographical, observation is made about the participants: "You really have to be from the Balkans to do something like this :)"
- The distinction between voluntary effort and other forms of breath-holding is highlighted: "“the longest breath held voluntarily under water using oxygen” Voluntarily is an important point here."