Science Questions

Are air cavities in the body a problem when diving deep?

Sun, 10th Apr 2011

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Question

Eelko asked:

Hi Naked Scientists,

 

I love your podcasts and listen to them regularly in my car to and from work. It's inspiring, intriguing and a wonderful way to spend some spare time that otherwise would've gone to waste!

 

In regard to your listener's questions section, I do have a question that you may be able to answer.

 

You probably heard about deep-sea diving with suits in which the divers breath fluids. The movie "The Abyss" portrays it wonderfully. The diver is put into a diving suit which is filled with an oxygen-rich fluid that he can breath. After some disorientation, the diver starts to breath the fluid and can dive to depths of up to hunderds or thousands of meters. (Don't you love sci-fi?)

 

Still, one thing puzzles me. There's more air in a body than just in your lungs. What about all the air in the Eustachian tubes in your ears? Won't your eardrums rip when the pressure changes that much and there's still air in those tubes? And what about the gasses in your bowls or stomache? Will they dissolve or will you also need some sort of an enema when you dive to those depths? Is it vital to burp so that all the gasses in your stomache are gone? And are there any other air bubbles inside a body that usually are harmless but could seriously injure someone at those depths?

 

Kind regards,

 

Eelko de Vos, the Netherlands

Answer

Chris -   It is a very good film and it does seem very futuristic, but it is actually partly reality.  These chemicals, these liquids do exist.  They're called perfluorocarbons.  They include fluorohexane for example, so a string of 6 to 8 carbon atoms with lots of flourines hanging off the side and they're very good at dissolving oxygen.  So, one way of doing this would be to instil these fluids into the respiratory tract and you saturate them with the oxygen, and then you move the fluid in and out, in the same way that you would when you were breathing.  

Why this is helpful is that when a person descends underwater, the pressure they feel from the surrounding water goes up and up, the deeper they go.  So, you have to therefore put the gas into the lungs to keep the lungs inflated, under progressively higher and higher pressures.  One consequence of this is that it drives other gases like nitrogen and things into the tissues at extremely high pressures which means that then when you decompress, those gases come out of solution in the tissues and form bubbles which can cause the bends, they can cause damage to the brain, and cause damage to bones and muscles and so on.  So if you use a fluid in the lung, because fluids are incompressible then you wouldn’t have the same problem because the fluid would withstand the pressure being applied by the outside water much better.

The issue with these fluids though is that they're not very good at removing CO2.  They're very good at putting oxygen in.  They're not good at getting carbon dioxide out and to compensate for the fact that they don't move CO2 very well, you'd have to move a lot of the fluid a lot of the time, and that's one of the major hold ups with doing this.  In terms of the liquid getting into other body cavities and body parts, this isn’t such a problem actually.  The eustachian tubes that you mentioned, they run between the back of the throat and the ear, so they would just fill up with the fluid anyway.  The other body cavities, well, they wouldn’t actually be exposed to the fluid directly because it will be in the respiratory tree.  So, there wouldn’t be a problem there and if there were any leakages of the fluid into other places, you would just pass it, I would think.  It certainly wouldn’t become part of the systemic circulation, so it should be okay.  

I make it sound like it’s all easy and a problem that's been solved.  It is being used in a limited way, but it’s certainly not mainstream yet by any stretch of the imagination.

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Eelko asked the Naked Scientists: Hi Naked Scientists, I love your podcasts and listen to them regularly in my car to and from work. It's inspiring, intriguing and a wonderful way to spend some spare time that otherwise would've gone to waste! In regard to your listener's questions section, I do have a question that you may be able to answer. You probably heard about deep-sea diving with suits in which the divers breath fluids. The movie "The Abyss" portrays it wonderfully. The diver is put into a diving suit which is filled with an oxygen-rich fluid that he can breath. After some disorientation, the diver starts to breath the fluid and can dive to depths of up to hunderds or thousands of meters. (Don't you love sci-fi?) Still, one thing puzzles me. There's more air in a body than just in your lungs. What about all the air in the Eustachian tubes in your ears? Won't your eardrums rip when the pressure changes that much and there's still air in those tubes? And what about the gasses in your bowels or stomache? Will they dissolve or will you also need some sort of an enema when you dive to those depths? Is it vital to burp so that all the gasses in your stomache are gone? And are there any other air bubbles inside a body that usually are harmless but could seriously injure someone at those depths? Kind regards, Eelko de Vos, the Netherlands What do you think? Eelko , Mon, 4th Apr 2011

You ask some good questions. first of all, there is actually a passage between your nose and ear.

"The Eustachian tube is a tube that originates in the back of the nose, runs a slightly uphill course, and ends in the middle ear space. The middle ear space is the hollowed out portion of the skull bone that contains the hearing apparatus and is covered on one side by the eardrum. In adults, the Eustachian tube is approximately 35 mm long (1.3 inches) and approximately 3 mm in diameter (less than 1/10 inch). Cartilage provides the supporting structure for the first two-thirds of the Eustachian tube, with the last third (the part closest to the middle ear space) being made of bone.

The tissue that lines the Eustachian tube is similar to that inside the nasal cavity and may respond the same way (swelling) when presented with similar stimuli. The Eustachian tube was named in honor of the 16th century Italian anatomiast Eustachius. Sources credit Almaceon of Sparta as the first to describe the structure in approximately 400 BC.

The primary function of the Eustachian tube is to ventilate the middle ear space, ensuring that its pressure remains at near normal ambient air pressure. The secondary function of the Eustachian tube is to drain any accumulated secretions, infection, or debris from the middle ear space. Several small muscles located in the back of the throat and palate control the opening and closing of the tube. Swallowing and yawning cause contractions of these muscles and help to regulate Eustachian tube function."

So there you have the explanation of that. When it comes to free gases in the tissues, especially oxygen, it's called the Oxygen window. 

And finally, here you can read about some, really remarkable, free diving guys/gals and their techniques. It's cool reading, as for why they don't get problems I believe to have to do with the limited time they dive. Free diving tips. By the way, we have them in the Nordic countries too? Very weird as we have a rather changing climate, but, there you are. Here's the records. Free diving records. But read this after you read about the tips, then you will know the differences.
==

Rereading you, yeah, but the pressure equals out between the trapped gas expanding in your lungs (ascenting), and the pressure outside your body (water in this case), even though it takes some slight time and you will need to yawn swallow or some other way equalize that pressure in your ears. And that's also why it's rather stupid to dive having a cold, at least like those people.  :) A free diver can get the 'bends' too, but he will have to do a lot of dives in a short period to get it. At 33 feet the volume of your breath is double a normal breath, using scuba wear.

"Your body always has nitrogen from the air you breathe dissolved in it, and the amount of nitrogen that is dissolved depends on the pressure on your body. That pressure comes from the weight of the atmosphere pressing on you when you're on the surface. As you descend in the water the weight of the water increases the pressure, and your body can then absorb more nitrogen (or any other gas you breathe) in proportion to the increased pressure. Double the pressure, and your body can absorb twice as much nitrogen. Of course your body can only absorb the nitrogen that is inhaled. When the pressure is reduced on ascent the extra gas will be lost. If the reduction in pressure is small enough or slow enough the gas will remain in solution and be carried to the lungs to be exhaled. If the reduction is too much or too fast the gas will come out of solution and form bubbles. All forms of decompression sickness, including the bends, are caused by those bubbles."

some divers use earplugs with a small hole in them allowing for equalizing the pressure and not getting the plugs wandering in by the pressure. "Another lower tech option is favoured by probably the UKs best ever competitive spearo; he puts a big dollop of vaseline in each ear before diving. This also keeps the water out whilst allowing pressure to equalise. I have never tried this method, but it seems to work for Pete (he is deaf as a post though." yor_on, Mon, 4th Apr 2011

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