Your Brain on Diving E-Book

Klaus M. Stiefel

• Herausgeber: Felicitas Hübner Verlag
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch
• Veröffentlichungsjahr: 2022

Seitenzahl: 66

Beschreibung

Biologist and technical diver Dr. Klaus M. Stiefel explains some exciting new insights into the workings of the human brain for the interested layperson. Topics include novel results on the mechanism causing the dreaded which can distort a diver's senses and the brain-mechanisms of controlling breathing and breath hold during freediving (apnea diving). The book also discusses new scientific results about the genetic adaptation of Southeast Asia's "sea gypsies" (the Bajao tribe) to extended breath hold diving.

Leseprobe

Imprint

Author: Klaus M. Stiefel

Title: Your Brain on Diving

Subtitle: New insights into the function of the human brain underwater

All rights reserved. Even the publication or reproduction of excerpts of any kind, apart from review citations, requires the permission of the publisher. This applies in particular to electronic or other reproduction, translation, distribution and making available to the public.

© 2022 by Felicitas Hübner Verlag GmbH (huebner-books), Apensen, Germany

Excerpts from the original German language edition “Gehirn extrem”, © 2019 by Felicitas Hübner Verlag GmbH (huebner-books), Apensen, Germany

Photos © by Klaus M. Stiefel

Cartoons “Synapsis” © by Anna Farell

Translation © by Klaus M. Stiefel

ISBN 978-3-941911-80-2

www.huebner-books.de

Table of Contents

Imprint

Diving and Brains: A Brief Intro

Inert Gas Narcosis

What Nitrogen Does to Brain Cells

Nitrogen-Altered Brain Waves

Whale Brains

Apnea

Breathing and the Brain

Oxygen Use

Fear and Loathing Underwater

The Hindbrain Again

Badjao Superpower

Human Free Diving Evolution

About the Author

Literature

Diving and Brains: A Brief Intro

I love to be underwater, to the point that I took up diving as a teenager and now spend time underwater almost every week, sometimes teaching scuba courses, and often filming and photographing the subaquatic world. I also have a burning desire to understand what goes on in our brains, so much that I took up neurobiology as the subject of my graduate studies in 1998 at the Max Planck Institute for Brain Research. The passions for diving and for neurobiology seemed disjoint at first, even to myself, but in recent years I have seen a number of fascinating overlaps.

We humans are, of course, land mammals, and sticking our head underwater and exposing ourselves to increasing water pressure will have effects on our bodies, some of which we were equipped to deal with by Mother Evolution; others catch our bodies off guard. As so often, the most intense and curious effects show up in our bodies’ most complex organ, the brain. Anybody who has scuba dived to more than about 30 meters will attest to the mind-spinning effects of inert gas narcosis.

When Felicitas Hübner and I planned a popular science book on extreme brain states, it was clear to me that I wanted to make the effects of diving on human brains one of the topics of the book. “Gehirn extrem” was released in 2019, with excellent illustrations by Anna Farell, twoof whichareincluded in this eBook as well. With German-speaking friends in the diving community, the book was well received, and many non-German-speaking diving friends nudged me to release an English-language version, or especially of the diving-related chapters, and this is the eBook in front of you. I have translated the two chapters on inert gas narcosis and breath hold and added a new chapter on the connection between fear and breathing.

Just like the German original “Gehirn extrem,” this is not a user manual on how to avoid inert gas narcosis when diving or how to hold your breath longer. But I think it’s the enlightened thing to try to understand what is going on in our heads if our states of mind differ from their normal states. Translating my own writings was a chance to re-read them. I’m usually a harsh critic of myself, but I am somewhat pleased: The mix between first-person “trip report” and objective neurobiological knowledge goes down easily. On top of that I present knowledge that should be well known to any trained diver, spiced up with cutting-edge and sometimes speculative neurobiological knowledge. Enjoy!

Dr. Klaus M. Stiefel

Dumaguete City, Philippines, February 2022

Divers at a depth of 50 meters on a reef in the Philippines.

Inert Gas Narcosis

It’s one of those paradisiacal early summer days unique to the Philippines: The air over the waters of the Pacific Ocean doesn’t move a bit, and the surface of the ocean is so still and flat that I can observe the corals around Malapascua Island from the island’s coast. I love this diving location in the north of the Cebu province of the Philippines.

Already at eight in the morning, the tropical sun is bathing the island in bright sunlight. The sunlight refracted on the cusps of the tiny waves paints a labyrinth of dancing lines onto the sand below. A school of damselfish races around the corals in the hip-deep water. Even closer to shore, in merely knee-deep water, an empty coconut shell drifts on the water surface above the seagrass.

But my plan today is not to explore the shallow waters of the Visayan Sea. I aim to dive deep!

Our scuba tanks – and I should definitely use a plural here – are filled, ready, marked with stickers, and lined up along a bamboo wall next to the dive shop. Our tanks don’t contain air like they do when going on regular, “recreational” scuba dives. My dive buddies Matt and David also don’t look as if they were preparing for a recreational dive: The pair is leaning against the bar of the dive shop, engulfed in an animated discussion of the long tables of dive depths and times written down in the notes written on waterproof paper laid out in front of them. The guys look relaxed but serious. After years of diving together, we have become friends; Matt was the one who taught me the advanced diving skills we will use today. The athletic Englishman with the hip beard has already put on his wetsuit and has strapped two dive computers and a compass to his forearms.

David briefly looks up from the discussion he is having with Matt and asks the captain of our dive boat, who is crossing the dive shop’s yard with two scuba tanks in his hands, if he has already brought the spare tanks on board. Even after many years abroad, David hasn’t lost his mild Irish accent. The captain assures David that all spare tanks are already on board and steadily walks onwards to the beach where our dive boat is moored. I rush to the dive shop’s equipment room and strap on my own two dive computers and double check that I have indeed entered the correct breathing gases for this dive.

We need this amount of preparation because our dive today will be a technical dive, a dive significantly deeper than a conventional scuba dive and with significantly more time spent at depth. This is the reason why we need all of these different (non-air) breathing gases: one for the deep part of the dive and two for our slow way up. The shallower we are when breathing a certain gas, the more oxygen it contains. We chose our gases in this way to make sure that the excess dissolved nitrogen will leave our bodies as smoothly as possible.

Why is this nitrogen a problem? Even though the atmosphere of Planet Earth contains 79% nitrogen, it barely plays a role in our physiology at the surface since it’s a rather chemically unreactive gas. This changes when we expose our bodies to increased pressure: When we reach 55 meters below the surface, which is the maximum planned diving depth for today, the ambient pressure will be 6.5 bar, or about 6½ times the pressure we are exposed to at the surface. Under these conditions, a vastly increased amount of nitrogen will dissolve in our bodily tissues. The longer and the deeper we dive, the more nitrogen we accumulate. This becomes a problem once we ascend: The nitrogen “bubbles out” just like the carbonation in a can of warming soft drink, and the bubbles can cause damage to our bodies. And something else happens: Nitrogen at depth does strange things to our nervous systems.