marine diving mammals

[cliffgollus]

Hi all,

I enjoyed Eric's current article on why marine diving mammals can go so long, so deep. I do not know if there is a mechanism to have him field questions so will put this in the forum. Question; is there any record of seals suffering SWB? If not, any thoughts why? The small lung volume was cited as needed to prevent nitrogen narcosis and getting bent, but doesn't blood (and tissue) also carry dissolved nitrogen? And why doesn't the oxygen become toxic at such extreme depth?

Thx, Cliff

 

[Stephan Whelan]

Hi!

You can contact Erik directly by clicking on the "email" link on the article under his photo. This will allow you to email him directly. In the meantime i'll contact him and see if he can get you a response that I can post here.

Cheer!

 

[efattah]

I might be able to answer some of the questions.

Seals SWB: There have been some cases of seals blacking out when they cannot find a breathing hole under the ice. This is not really shallow water blackout, but just blackout. The shallow water has nothing to do with it. The seals die when this happens.

High amounts of dissolved nitrogen occur when the ppN2 in the lungs is huge, and then the blood flows past the lungs/aveoli, and absorbs the N2. If the lungs are collapsed, there is no gas exchange from lungs to blood, so high pressures of N2 are never exposed to the blood, and thus the blood does not absorb N2 and cannot carry the N2 to the tissues either.

O2 toxicity works the same as the N2. Collapsed lungs prevent gas exchange from the lungs to the blood, preventing huge amounts of O2 to dissolve in the blood.

In short, collapsed lungs prevent all types of toxicities and narcosis, and collapsed lungs also prevent DCS and all gas-pressure related anomalies.


Eric Fattah
BC, Canada

 

[Stephan Whelan]

Here is the first part of Erik's answer:

There have been no recorded cases of SWB in seals or in any other freediving
mammal. This is primarily due to the fact that these depths, deep though
they may be, are actually very conservative since the mammal must budget for
potential problems either on the way down or on the way up: these problems
would usually involve escaping from predators (very costly in oxygen
consumption!) or searching for a hole in the ice.

 

[cliffgollus]

Thanks for both answers, especially the idea of a "conservative" dive to give room for evading predators, etc - my kind of conservative!

One other thing Eric mentioned was the theoretical limit to how deep someone can go, and then gave the example of Pippin blasting past it. I read somewhere a theory that on very deep dives, Pippin's lungs avoided being "squeezed" by filling with plasma. There was no data presented to support this, and such a thing sounds very much like pneumonia. Any thoughts on how divers exceed the theoretical limits?

Thx, Cliff