M value

[The Iceni]

Alban once bubbled...
. . . one thing that has puzzled me though is how the whales blood gets supersaturated from a breath hold dive ?

Also would the whale slow down it's heart rate reducing prefusion to the tissues ?

Hi Alban,

1) The lungs are compressed to ambient pressure (resulting in mass transfer of blood into the pulmonary capilliary bed from the peripheral circulation) causing an increase in the partial pressure of all the gasses within them. Of course this moves into solution in the blood and tissues.

Although this does increase nitrogen loading, there is only one "lungful" of air from which this nitrogen can come. It is not continuously being topped up by gas at ambient pressure from a regulator. So, as I see it, a whale will will not continue to ongas at depth and they simply surface when they run out of oxygen (when the pp CO2 exceeds a set threshold). Because nitrogen loading is not great the risk of DCI is minimal.

Therefore a freediver will not get bent easily, if at all.

2) All diving mammals, including humans, exhibit the Herring Bruer (spelling?) reflex, which slows the heart rate on immersion.

I think that about covers it. ut:

 

[Dr Deco]

Dear Alban:

Supersaturated

It is interesting that you also noted that. It is one of the “physiological” errors in the model. No, the blood will not become saturated on one lungful and neither will the tissues.

As I have said in the reply on “Models” in another thread, the models are only as good as the biophysical basis. Mathematical elegance (= “cool”) is often confused with correctness. I have seen the basic form of e = mc2 derived with high school algebra. It is not complicated, but the result was very important.

Dr Deco :doctor:

 

[Alban]

Thanks Doc's

Fascinating stuff Dr T you are quite correct I must admit I did consider if this was possible then decided against it without researching it further. A Blue Whale has a 2,000 ltr lung capacity it dives to 200 mts I make that reduced to 100 lts
Consider the Sperm Whale it can dive to 2,000 mts !!

http://rbcm1.rbcm.gov.bc.ca/programs/whales/t-activity-5.html

I must be taking in something Dr D tells me.

Thanking you for your time Alban

 

[The Iceni]

Now a question for you, Alban.

Do fish, lobsters and crabs get DCI when they are brought to the surface?

 

[jeffsterinsf]

Dr Paul Thomas once bubbled...
Now a question for you, Alban.

Do fish, lobsters and crabs get DCI when they are brought to the surface?

No, usually they get boiled or broiled...

 

[Alban]

Hi Dr T.

Interesting question I am not sure if a crab counts as a dive buddy but lets look at this from a decompression angle , your crab would need to on gass a partial pressure of + 0.79 so unless you intend to buddy breathe with him I am not sure where he will get this from ? I assume the ocean will absorb gas as Henry's law from the atmosphere above at 1 ata . I can see that it moves and this may vary in concentration, the surface and where the waves break being higher in O2 than the depths.
Now the key question is will the partial pressure of a disolved gas increase with hydrostatic pressure ? ( free phase gas in microbubbles may be different ) I would say No you can bring your crab straight to the surface. But if you tapped him to a rocket you would probably end up with bubble and squeek.:boom:

Alban

 

[Dr Deco]

Dear Alban:

Indeed any sea creature brought up from the depths would not be over saturated with gas. The partial pressure of a dissolved gas does not vary with depth. Gas bubbles from breaking waves do not descend much below 100 fsw.

It is curious that crabs have been used in diving experiments to test for bubble formation. The APPENDIX (from the Decompression Physiology class) shows that crabs whose movement is restricted do not form gas bubbles. Those that can move form quite a few.

In the section http://www.doctordeco.com/archives/000016.html, one can find the article “Decompression Gas Phase Formation in Simulated Microgravity” (the last paper of the group). In it, various experiments, including the one on crabs, are described.
Dr Deco :doctor: