Mr T's Wild Freedive

[Storker]

Not to mention, if you release you're 02 before you ascend

Sorry, what does this mean? I'll readily admit that English is my second language, but I like to believe that I'm better at writing and reading science in English than in my primary language. And this just doesn't make sense to me.

 

[IncreaseMyT]

It means to breath out doc.

 

[saxman242]

It is the exact same it is no different. There are 2 things that can cause a shallower water blackout, not to be confused with a deep water blackout:

#1 Not enough 02
#2 Not enough pressure to get the 02 to the brain

I really have to go, I told myself I would not spend all day educating but here I am. I leave you with this, you should really read it:

https://www.degruyter.com/downloadpdf/j/tnsci.2013.4.issue-3/s13380-013-0130-5/s13380-013-0130-5.pdf

I also recommend looking into the citations.

With shallow water blackouts often being a result of a reduced co2 response because of hyperventilating purging co2 build up, wouldnt a freediver taking a breath from a tank be much more driven by a co2 response to get up and get air and far less likely to push themselves to the point of swb?

 

[IncreaseMyT]

Reduced C02 response? No you are confused again, they are talking about breathing up too much before dive.

You can just not have enough oxygen. Which is why it is not a good idea to go down to 70 feet take a breath off a reg, let out some air, dive for a while then ascend. Because your 02 stores will be depleted and this is pronounced by and extreme reduction in pressure on ascent.

 

[saxman242]

Reduced C02 response? No you are confused again, they are talking about breathing up too much before dive.

You can just not have enough oxygen.

Shallow water blackouts occurs due to not enough oxygen. This is often predicated by someone who has intentionally hyperventilated prior to the dive to purge built up co2 in the lungs beyond the normal tidal volume as it's the concentration of this co2 that drives the body to feel like you're out of air. Essentially, the freediver runs out of air before they feel like they're out of air, so their actions (intentionally staying under too long) are a result of tricking their bodys response.

The hypothetical that I'm posing is that by breathing off a tank at the end of a long breath hold dive, they are not hyperventilating again and not purging all that built up co2 reserves beyond the normal tidal volume. As such, the need to breath due to co2 build up when come about with much higher amount of unmetabolized oxygen remaining in the lungs, reducing the chance of a swb.

We are way deep in the weeds of the hypothetical now, but if we are going to be discussing behaviors and cause/effect, it is an interesting thought exercise.

 

[IncreaseMyT]

"Elite breath-hold divers are unique athletes challenged with compression induced by hydrostatic pressure and extreme hypoxia/hypercapnia during maximal field dives. The current world records for men are 214 meters for depth (Herbert Nitsch, No-Limits Apnea discipline), 11:35 minutes for duration (Stephane Mifsud, Static Apnea discipline), and 281 meters for distance (Goran Čolak, Dynamic Apnea with Fins discipline). The major physiological adaptations that allow breath-hold divers to achieve such depths and duration are called the “diving response” that is comprised of peripheral vasoconstriction and increased blood pressure, bradycardia, decreased cardiac output, increased cerebral and myocardial blood flow, splenic contraction, and preserved O2 delivery to the brain and heart. This complex of physiological adaptations is not unique to humans, but can be found in all diving mammals. Despite these profound physiological adaptations, divers may frequently show hypoxic loss of consciousness. The breath-hold starts with an easy-going phase in which respiratory muscles are inactive, whereas during the second so-called “struggle” phase, involuntary breathing movements start. These contractions increase cerebral blood flow by facilitating left stroke volume, cardiac output, and arterial pressure. The analysis of the compensatory mechanisms involved in maximal breath-holds can improve brain survival during conditions involving profound brain hypoperfusion and deoxygenation."

 

[IncreaseMyT]

"
Abstract
To investigate the mechanisms responsible for fluctuations in arterial pressure and sympathetic nerve activity that occur during obstructive sleep apnea, we studied neurocirculatory responses to Mueller maneuvers and breath holds in conscious humans. During 20-s Mueller maneuvers at -40 mmHg, mean arterial pressure fell initially (-11 +/- 3 mmHg) and then rose above baseline (+8 +/- 3 mmHg) on release of the inspiratory strain. Sympathetic outflow to skeletal muscle was almost completely suppressed during the initial moments of the maneuver and rose to more than three times the baseline level at the termination of the maneuver. Simple 20-s breath holds were accompanied by time-dependent increases in both arterial pressure (+11 +/- 3 mmHg) and sympathetic nerve activity (> 3 times baseline). The administration of supplemental O2 greatly attenuated the increases in arterial pressure and sympathetic nerve activity during Mueller maneuvers and breath holds. We conclude that carotid chemoreflex stimulation is the primary mechanism responsible for apnea-induced sympathetic activation during wakefulness and that it may contribute importantly to the sympathetic activation that accompanies sleep-disordered breathing."

Neurocirculatory consequences of negative intrathoracic pressure vs. asphyxia during voluntary apnea. - PubMed - NCBI

 

[saxman242]

Are you trying to suggest that changes in arterial pressure are the cause the body's drive to breath instead of reacting to co2 levels or are you key word searching journals for breath holding and posting whatever you find?

 

[johndiver999]

So affinity as used here, is associated with the chemical attraction between oxygen and muscle myoglobin? Is there a change in affinity with respect to hemoglobin? If so the two processes would seem to be working at odds with each other.

Although it is dangerous for a free diver to use air at depth, it is hard for me to comprehend how the purging of co2 and intake of additional oxygen will not result in the potential to extend the dive duration. What if the freedive takes
Two hits, will his dive not be extended? What if he takes 5 hits from a reg? Does mr t still claim that the duration of the dive will not be extended?

 

[IncreaseMyT]

So affinity as used here, is associated with the chemical attraction between oxygen and muscle myoglobin? Is there a change in affinity with respect to hemoglobin? If so the two processes would seem to be working at odds with each other.

Although it is dangerous for a free diver to use air at depth, it is hard for me to comprehend how the purging of co2 and intake of additional oxygen will not result in the potential to extend the dive duration. What if the freedive takes
Two hits, will his dive not be extended? What if he takes 5 hits from a reg? Does mr t still claim that the duration of the dive will not be extended?

Well we already went over that, that person has become a scuba diver at that point, you are no longer free diving. This was already covered. Now all you have to worry about is the buoyancy issue and making sure you stop holding your breath, if you keep breathing off the reg.