Mr T's Wild Freedive

[tridacna]

Will someone please move this whimsical nonsense to the pub? It deserves better treatment that only the Pub can provide.

 

[IncreaseMyT]

Will someone please move this whimsical nonsense to the pub? It deserves better treatment that only the Pub can provide.

How about just not read the thread then?

I think you are quite right on this. A deep free diver may shoot up after one single inhale unless he holds up to something. If he is holding the scuba diver, I guess it is also a danger for that generous guy, who might be pulled up at a too fast speed.
As a newb I never experienced that and so I launched this post. It is just for discussion. Different opinions bring us together to enjoy thinking.
Thanks for your comments and enjoy diving with your son

 

[IncreaseMyT]

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?

Nope, I am saying that 02 attenuates those changes which proves the inverse that shallow water blackouts are in fact commonly due to lack of 02, hypoxia

Hypoxia, in medicine, condition of the body in which the tissues are starved of oxygen. In its extreme form, where oxygen is entirely absent, the condition is called anoxia.

There are four types of hypoxia: (1) the hypoxemic type, in which the oxygen pressurein the blood going to the tissues is too low to saturate the hemoglobin; (2) the anemic type, in which the amount of functional hemoglobin is too small, and hence the capacity of the blood to carry oxygen is too low; (3) the stagnant type, in which the blood is or may be normal but the flow of blood to the tissues is reduced or unevenly distributed; and (4) the histotoxic type, in which the tissue cells are poisoned and are therefore unable to make proper use of oxygen. Diseases of the blood, the heart and circulation, and the lungs may all produce some form of hypoxia.

The hypoxemic type of hypoxia is due to one of two mechanisms: (1) a decrease in the amount of breathable oxygen—often encountered in pilots, mountain climbers, and people living at high altitudes—due to reduced barometric pressure (see altitude sickness) or (2) cardiopulmonary failure in which the lungs are unable to efficiently transfer oxygen from the alveoli to the blood.

In the case of anemic hypoxia, either the total amount of hemoglobin is too small to supply the body’s oxygen needs, as in anemia or after severe bleeding, or hemoglobin that is present is rendered nonfunctional. Examples of the latter case are carbon monoxide poisoning and acquired methemoglobinemia, in both of which the hemoglobin is so altered by toxic agents that it becomes unavailable for oxygen transport, and thus of no respiratory value.



In histotoxic hypoxia the cells of the body are unable to use the oxygen, although the amount in the blood may be normal and under normal tension. Although characteristically produced by cyanide, any agent that decreases cellular respirationmay cause it. Some of these agents are narcotics, alcohol, formaldehyde, acetone, and certain anesthetic agents.

hypoxia | Definition, Types, & Physiological Effects

So again, like I said, either not enough 02, or not enough pressure.

 

[saxman242]

Nope, I am saying that 02 attenuates those changes which proves the inverse that shallow water blackouts are in fact commonly due to lack of 02, hypoxia



hypoxia | Definition, Types, & Physiological Effects

So again, like I said, either not enough 02, or not enough pressure.

No, evidence of one thing does not prove the inverse is true(not that shallow water blackouts are the inverse of the Mueller maneuver anyway), however, I'm not saying shallow water blackouts is a result of co2 buildup or that it isn't the result of O2 shortages. I'm saying that the mechanism that drives the behavior to replenish O2 is a result of co2 buildup and pointing out that in the case of shallow water blackouts, an intentional behavior to suppress the drive to replenish O2 is often in play. Taking a breath off a tank would negate that behavior, changing the relationship between the point of when someone suffers a shallow water blackouts due to low O2 levels and the perception of need to breath due to co2 levels.

I'm discussing the behavior regarding co2 that effects the mechanism regarding O2.

 

[IncreaseMyT]

No, evidence of one thing does not prove the inverse is true, however, I'm not saying shallow water blackouts is a result of co2 buildup. I'm saying that the mechanism that drives the behavior to replenish O2 is a result of co2 buildup and pointing out that in the case of shallow water blackouts, an intentional behavior to suppress the drive to replenish O2 is often in play. Taking a breath off a tank would negate that behavior, changing the relationship between the point of when someone suffers a shallow water blackouts due to low O2 levels and the perception of need to breath due to co2 levels.

I'm discussing the behavior regarding co2 that effects the mechanism regarding O2.

Then you tell me why judges watch professional free diving competitions and look for signs of hypoxia, when a shallow water black out is the biggest worry. They actually pull them if they find any signs of hypoxia.

There is no doubt, that you can dive longer on a full breath, so swimming around on a half a breath, after you exhaled to adjust your buoyancy is not a good idea. I don't understand why you think it would not increase your chance of hypoxia? Thats what a blackout is, loss of motor control, you might even have seizures.

So now you have no idea how long you can stay down. You don't just free dive to 70 feet on a whim lol. You know exactly how long you stay down, you are watching your watch, hopefully.

So you're telling me, that taking a half breath off a reg, at 70 feet, will not increase your chance of a shallow water blackout? This is your argument?

Remember 10 % of professionals get pulled from competition, professionals.

 

[Celt]

No, it is not. It can all be explained using high school and freshman college level science.


Ok, here's another case where you've got it bass-ackwards. No matter if the person in question is freediving or on scuba, nitrogen is physically dissolved in the blood while oxygen is predominantly captured by the diver's red blood cells for transport to the tissues. In the tissues, nitrogen is absorbed and stays there while oxygen is metabolized into CO2. The CO2 is transported back to the lung alveoli, where it's transferred to the gas in the alveoli. The nitrogen stays in the tissues until the diver starts to ascend, at which time it transfers from the tissues into the blood and is transported back to the lung where it transfers to the gas in the alveoli.

Now, for a scuba diver the O2 won't have time to deplete dramatically and the CO2 won't have time to accumulate dramatically because we breathe continuously. So the expired air contains some 17% O2 and some 4% CO2, and WRT lung gas composition we're pretty much the same as at the surface. A freediver doesn't ventilate their lungs, so they experience a more serious depletion of O2 and a more serious accumulation of CO2. Given the relatively short duration of a freedive and the rather slow diffusion of nitrogen from the alveoli to the blood, the amount of nitrogen transferred from the lungs to the blood (and other bodily fluids, cue General Jack D. Ripper) is rather minute, from a total volume perspective. Unless we're talking about repeated freedives (Taravana syndrome), where the amount of nitrogen dissolved in the tissues becomes significant from a DCS POV, but far from necessarily from a lung gas composition POV. And it's the combination of low FO2 in the lungs and decreasing P leading to a too low pPO2 which is responsible for shallow water blackout for freedivers.

Your apparent complete confusion over gas compression, gas transport and the basic physics and physiology of diving doesn't strengthen your case.

Thank you for that. for a while there Mr.T was starting to get into my head.

 

[saxman242]

No, I'm not arguing that hypoxia isn't a problem.

I'm saying that there isn't anything inherrent in being a freediver breathing off a tank that increases your risks of a shallow water blackout compared to a diver doing the same. (This is not be taken as saying that there aren't risks in a freediver doing this, but the biggest risk would appear to be embolism in an uneducated freediver) I'm further postulating that in the case of a freediver that hyperventilates prior to making a dive then breathing off a tank briefly could change the relationship between levels of O2 and the drive to breathe.

 

[IncreaseMyT]

No, I'm not arguing that hypoxia isn't a problem.

I'm saying that there isn't anything inherrent in being a freediver breathing off a tank that increases your risks of a shallow water blackout compared to a diver doing the same. I'm further postulating that in the case of a freediver that hyperventilates prior to making a dive then breathing off a tank briefly could change the relationship between levels of O2 and the drive to breathe.

Its not the tank, its the fact now you only have a half a breath. Sigh. When do you go up?

 

[saxman242]

Its not the tank, its the fact now you only have a half a breath. Sigh.

Shall we have a conversation about a half breath from a tank at deeper than 30 feet having more air (and all its constituent gases) in it than a full breath at the surface?

 

[IncreaseMyT]

Shall we have a conversation about a half breath from a tank at deeper than 30 feet having more oxygen in it than a full breath at the surface?

You will have no idea when to go up lol. When free diving you are passed the urge to breathe, the mammalian reflex.

Hopefully someone can answer when to go up cause it is really important. Wait too long, you could suffer hypoxia.

Are you saying treat a half breath at depth the same as a full at the top? I will let you try it first