In conclusion, I’ll talk about two things I’ve never even done: scuba (darn) and the bends (thank god). These underwater phenomena summarize very well the concepts I’ve outlined. As a note, this page would be set to some of my favorite music, but amazonkers.com and towersucks.com don’t have sound samples for “Underwater Love” and “The Bends.” Shucks.
Back in the days when everything was still so simple, people devised novel ways of exploring the ocean floor. Take the little guy below, for example. The hood over his head connects him to surface air, and he can breathe fine, right? Wrong.
We would reason that a deep diver is subjected to increased “atmospheric” water pressure, a great force pressing in on his chest. Remember, water is heavier than air and exerts much more pressure? To give an idea, atmospheric pressure increases by 760 mm Hg every 30 feet below sea level in sea water. At 2 feet, the atmospheric pressure will have increased 25 mm Hg to 785 mm Hg. It is generally accepted that below 2 feet, a diver breathing through a tube (a snorkel) will have extreme difficulty overcoming the weight of the water above him. Providing the air tube does not collapse, it provides atmospheric air at a lower pressure than the pressure pressing in on the thorax. At resting (where an equilibrium should occur), the lungs would have to expand to great proportions to equalize outside pressure. The little guy would try to take a breath and the great pressure would prevent his lungs from expanding to this size. If he was lucky at all, he might experience “rapture of the deep” for a few moments, but more likely he would suffocate sooner.
The image at right shows that for every 33 feet you descend under sea water, atmospheric pressure increases by 1 atmosphere (760 mm Hg). This is a serious gradient, and detrimental to life. Finally, after enough people popped underwater, someone invented scuba (self-contained underwater breathing apparatus). Compressed air in a tank equalizes with the water pressure so the lungs can expand against the crushing force of deeeeep water. Scuba allows people to explore depths for longer periods of time, but it also presents serious potential problems, namely decompression sickness (also called Caisson’s disease and “the bends”) and air embolism (Marieb 746).
What is, or are “the bends?”
Imagine you are scuba diving. The tank on your back is small but weighs a ton, probably because enough gas to fill a phone booth is compressed inside it, at about 3000 psi. As you descend, the pressure and amount of gas entering your lungs is harmlessly increased. Keeping the law of partial pressures in mind, you know that the partial pressures of all atmospheric gases entering your lungs are increased across the board. Henry’s law explains why more gas will be forced into solution in the body tissues.
Nitrogen levels are of concern. Nitrogen dwindles in lipid-rich tissues like the central nervous system (brain/spinal cord), bone marrow, fat, and dissolved in blood, and at prolonged concentrated levels causes “rapture of the deep,” a sort of drunken stupor. You’ve been under 100 feet for an hour already, and have just realized that you’ve been staring at the same coral for several minutes. You are suffering nitrogen narcosis. Panicking, you begin a hasty ascent. Oh no. You’ve forgotten to go slow, to gradually decompress your tank. The partial pressure of nitrogen drops swiftly, and a sharp gradient forms between nitrogen in the bloodstream (lowered) and nitrogen dissolved in fatty tissue (high). Nitrogen “boils” out of the tissues, creating emboli (bubbles) in bones, joints, and muscle. The pain seems to shadow the itching, coughing, skin rash, and seizures. At the surface, you scream, you bob in the water for a few moments, and quickly you drop into shock.
One big rule of scuba diving is to “keep breathing.” As chemistry whizzes, we know why: Boyle’s law. At one depth, the pressure in the lungs will be appropriate for the ambient pressure. If one holds the breath and ascends, the pressure in the lungs will still be high, but the ambient pressure will drop. The lungs will expand, and alveoli may pop. If an alveoli ruptures in such a way that an open bridge is formed between outside air and the bloodstream, when a breath is taken at surface, air emboli bubble into circulation. Seizures, localized motor and sensory deficits, heart attack, and unconsciousness are likely results (Marieb 746). It follows naturally that many people drown when unconscious in water…
These horrors do not usually occur when people are properly trained to scuba dive. Most divers are aware of the gas laws that influence their underwater adventure. In obedience of these laws, they are able to maintain a healthy, balanced physiological state even at deep depths.
Hopefully, these concepts come together with some meaning for you. I wouldn’t have wasted so much time making a website if it wasn’t interesting for me. I couldn’t begin to include all the fascinating tidbits I stumbled upon, and believe me there are more. For a start, check out my links page to see where I got some of my ideas. Yogic breathing, didjeridu circular breathing, more physiology, scuba links, and even some meaningful and beautiful quotes on breathing are accessible to you. Thanks for bwheazing through my site.
Last updated 5/21/03, before that, 3/13/01
- BREATHING TIPS.
Maybe you’re not doing it right.
- JOHN HOPINKS INTERACTIVE RESPIRATORY PHYSIOLOGY.
Why didn’t I just copy their website?
- ALLYN & BACON’S RESPIRATORY SYSTEM.
Because I copied this website instead!
- INSPIRING QUOTATIONS ON BREATHING/RESPIRATION.
It doesn’t get much better than this…
- ART OF BREATHING.
Testimonials from those who attest “it works!”
- DIDJERIDU TUTORIAL ON CIRCULAR BREATHING.
Now is there really such a thing?
- CIRCULAR BREATHING: A METHOD BY DR. ROBERT S. SPRING, DMA.
Okay, maybe it is possible.
- ACID BASE AND BLOOD GAS ANALYSIS .
A journal? Lecture notes? A recent archeological find?
- AN EXPLANATION OF PRESSURE AND THE LAWS OF BOYLE, CHARLES, DALTON, AND HENRY.
Complete overview with missing images and self-tests,
by Lawrence Martin, M.D.
- WATER AND THE PHYSICAL LAWS THAT GOVERN ALL DIVERS.
More from Lawrence Martin, M.D.
HEIN, Morris, Leo R. BEST, Scott PATTISON, and Susan ARENA. INTRODUCTION TO GENERAL, ORGANIC, and BIOCHEMISTRY. Pacific Grove: BROOKS/COLE: 1997
KAPIT, Wynn, Robert I. MACEY, and Esmail MEISAMI. The PHYSIOLOGY COLORING BOOK. Menlo Park: ADDISON WESLEY: 1987
KIMBER, Diana Clifford, Caroline E. STACKPOLE, et al. TEXTBOOK OF ANATOMY & PHYSIOLOGY. New York: MACMILLAN: 1948
MARIEB, Elaine N. HUMAN ANATOMY & PHYSIOLOGY. Redwood City: BENJAMIN/CUMMINGS: 1992
MARIEB, Elaine N. HUMAN ANATOMY & PHYSIOLOGY LABORATORY MANUAL. Menlo Park: ADDISON WESLEY: 1999
VISHNUDEVANANADA, Swami. The COMPLETE ILLUSTRATED BOOK OF YOGA. New York: BELL PUBLISHING: 1960