Are air-containg cavities a problem when diving deep?

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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?
« Last Edit: 04/04/2011 18:30:04 by _system »


Offline yor_on

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Are air-containg cavities a problem when diving deep?
« Reply #1 on: 04/04/2011 21:04:40 »
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."
« Last Edit: 04/04/2011 21:40:16 by yor_on »
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