Mr T's Wild Freedive

[IncreaseMyT]

No. You make the claim, you provide the evidence. That's how it works, and if you really were working in science you'd know that.

I did provide the evidence. All in one post, neatly.

 

[The Chairman]

Affinity is a term often used in endocrinology,

We are not discussing endocrinology. Charles law doesn't care for "affinity". Partial Pressure is the term used by pulmonologists to describe the phenomena we're discussing. It's too bad you can't be "bothered" to use the proper vernacular. So it's not that we can't learn, but that you can't teach, or have nothing to teach.

 

[IncreaseMyT]

We are not discussing endocrinology. Charles law doesn't care for "affinity". Partial Pressure is the term used by pulmonologists to describe the phenomena we're discussing. It's too bad you can't be "bothered" to use the proper vernacular. So it's not that we can't learn, but that you can't teach, or have nothing to teach.

Sigh

This report examines the evidence for the presence of oxygen stores in the lungs, blood and systemic musculature of diving mammals, the modifications in the respiratory functions of blood that may be important in utilizing the lung and blood oxygen stores, and the potential importance of the oxygen stores and the respiratory functions of blood in supporting short-duration, aerobic dives. Increasing oxygen stores by increasing lung volume does not occur in diving mammals. The long-duration diving whales have small lung volumes which results in lung collapse during dives and the seals dive following partial expiration which produces the same effect. The short-duration diving dolphins, porpoises and rodents have lung volumes comparable to terrestrial mammals, dive following inspiration and appear to use the lungs as an oxygen store. Adaptations in the oxygen affinity of the blood parallel the modifications in lung volume. Where the lungs do not represent a potential oxygen store the oxygen affinity is low, maximizing the unloading of oxygen while maintaining a high tissue oxygen tension. Where the lungs do represent an oxygen store, the affinity is high, maximizing the uptake of oxygen from the alveolar space. Increases in the concentration of respiratory pigment in the blood and in muscle are important adaptations in diving mammals. The blood oxygen stores in diving mammals vary from near normal to over three times normal for terrestrial mammals while the muscle oxygen stores vary from near normal to nearly ten times normal. The degree to which the blood and muscle oxygen stores are increased can be equated to the duration of the dive and demands for oxygen; longer duration divers and those with higher metabolic demands have greater oxygen stores than divers that remain submersed for shorter periods or have lower rates of oxygen utilization.

https://www.researchgate.net/publication/16825751_Respiratory_adaptations_in_diving_mammals

Like I said, when free diving the affinity for 02 offsets the fact that it has compressed.

 

[IncreaseMyT]

Abstract
The ability of diving mammals to forage at depth on a breath hold of air is dependent on gas exchange, both in the lung and in peripheral tissues. Anatomical and physiological adaptations in the respiratory system, cardiovascular system, blood and peripheral tissues contribute to the remarkable breath‐hold capacities of these animals. The end results of these adaptations include efficient ventilation, enhanced oxygen storage, regulated transport and delivery of respiratory gases, extreme hypoxemic/ischemic tolerance, and pressure tolerance. © 2011 American Physiological Society. Compr Physiol 1:447‐465, 2011.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/cphy.c091003

 

[almostDIR]

Yep the PARTIAL PRESSURE is the correct term to use here. "affinity" just confuses you and leads to misunderstandings

 

[IncreaseMyT]

Finally, a team led by Jay Storz, a molecular biologist at the University of Nebraska in Lincoln, studied the haemoglobin of deer mice (Peromyscus maniculatus)3. Deer mice that live at different altitudes have different versions of haemoglobin, and the high-altitude version has a higher affinity for oxygen than the haemoglobin of deer mice that live at low altitudes. Storz found that 12 mutations, grouped in three clusters, were responsible for the two variations.

https://www.nature.com/news/making-the-most-of-muscle-oxygen-1.13202

 

[IncreaseMyT]

Myoglobin (Mb) is an oxygen binding protein found in vertebrate skeletal muscle, where it facilitates intracellular transport and storage of oxygen. This protein has evolved to suit unique physiological needs in the muscle of diving vertebrates that express Mb at much greater concentrations than their terrestrial counterparts. In this study, we characterized Mb oxygen affinity (P50) from 25 species of aquatic and terrestrial birds and mammals. Among diving species, we tested for correlations between Mb P50 and routine dive duration. Across all species examined, Mb P50 ranged from 2.40 to 4.85 mmHg. The mean P50 of Mb from terrestrial ungulates was 3.72±0.15 mmHg (range 3.70–3.74 mmHg). The P50 of cetaceans was similar to terrestrial ungulates ranging from 3.54 to 3.82 mmHg, with the exception of the melon-headed whale, which had a significantly higher P50 of 4.85 mmHg. Among pinnipeds, the P50 ranged from 3.23 to 3.81 mmHg and showed a trend for higher oxygen affinity in species with longer dive durations. Among diving birds, the P50 ranged from 2.40 to 3.36 mmHg and also showed a trend of higher affinities in species with longer dive durations. In pinnipeds and birds, low Mb P50 was associated with species whose muscles are metabolically active under hypoxic conditions associated with aerobic dives. Given the broad range of potential globin oxygen affinities, Mb P50 from diverse vertebrate species appears constrained within a relatively narrow range. High Mb oxygen affinity within this range may be adaptive for some vertebrates that make prolonged dives.

Myoglobin oxygen affinity in aquatic and terrestrial birds and mammals

 

[The Chairman]

As a caveat, there are many incredible physicians on ScubaBoard who fully understand diving physiology, pulmonology use the right terminology and don't attempt to brow beat into believing they are "right". The biggest problem with a free diver breathing off of a regulator at depth would be the potential to experience a barotrauma to their lungs, perchance to die.

Staying down longer would also expose them to the possibility of DCS, and adding this to the frequent compression and decompression that is part and parcel of free diving can expose them to the phenomenon of "bubble pumping" which can cause an gas embolism with stroke like effects.

As many times as I have been in the water with free divers, both as a safety and as a friend, I've never had a serious free diver request air from me. What's the point of free diving if you have to cheat?

 

[IncreaseMyT]

Yep the PARTIAL PRESSURE is the correct term to use here. "affinity" just confuses you and leads to misunderstandings

 

[IncreaseMyT]

The biggest problem with a free diver breathing off of a regulator at depth would be the potential to experience a barotrauma to their lungs, perchance to die.

Not really, as @TBone has discussed in depth on this board before, unless you purposely hold your breath your body will most likely reflexly exhale the gas it needs to exhale.

Blacking out does occur 10% of the time in professional free divers, I can only imagine what number is on recreational divers. Not to mention, if you release you're 02 before you ascend. Gotta at least double your risk.