Directories | Web | Images | Groups | News | Shopping | Local

Enter your search keyword(s):

 



(formerly Encyclopedic directory)
Freediving
Home / Top / Sports / Water Sports / Freediving See also:
Related articles

Edit | Discuss Article

Apnea

Apnea (British spelling - apnoea) is the absence of external breathing. During apnea there is no movement of the muscles of respiration and the volume of the lungs initially remains unchanged. Depending on the patency of the airways there may or may not be a flow of gas between the lungs and the environment; gas exchange within the lungs and cellular respiration is not affected. Apnea can be voluntarily achieved (i.e., "holding one's breath"), drug-induced (e.g., opiate toxicity), mechanically induced (e.g., strangulation), or it can occur as a consequence of neurological disease or trauma.

Under normal conditions, humans cannot store much oxygen in the body. Apnea of more than approximately one minute's duration therefore leads to severe lack of oxygen in the blood circulation. Permanent brain damage can occur after as little as three minutes and death will inevitably ensue after a few more minutes unless ventilation is restored. However, under special circumstances such as hypothermia, hyperbaric oxygenation, apneic oxygenation (see below), or extracorporeal membrane oxygenation, much longer periods of apnea may be tolerated without severe consequences.

Untrained humans cannot sustain voluntary apnea for more than one or two minutes. The reason for this is that the rate of breathing and the volume of each breath are tightly regulated to maintain constant values of CO2 tension and pH of the blood. In apnea, CO2 is not removed through the lungs and accumulates in the blood. The consequent rise in CO2 tension and drop in pH result in stimulation of the respiratory centre in the brain which eventually cannot be overcome voluntarily. However, tolerance of apnea can be trained. The ancient technique of free-diving requires breath-holding and trained free-divers can indeed hold their breath for up to seven minutes. An apneist, in this context, is someone who can hold his breath for a long time.

Many people have discovered, on their own, that voluntary hyperventilation before beginning voluntary apnea allows them to hold their breath for a longer time. Some of these people incorrectly attribute this effect to increased oxygen in the blood, not realizing that it is actually due to a decrease in CO2 in the blood and lungs. Blood leaving the lungs is normally fully saturated with oxygen, so hyperventilation of normal air cannot increase the amount of oxygen available. Lowering the CO2 concentration increases the time before the respiratory center becomes stimulated, as described above.

This error has led some people to use hyperventilation as a means to increase their diving time, not realizing that there is a danger that their body may exhaust its oxygen while underwater, before they feel any urge to breathe, and that they can suddenly lose consciousness as a result. If a person loses consciousness underwater, especially in fresh water, there is a considerable danger that they will die by drowning.

Table of contents
1 Apneic oxygenation
2 References
3 See also
4 External links

Apneic oxygenation

Because the exchange of gases between the blood and airspace of the lungs is independent of the movement of gas to and from the lungs, a sufficient amount of oxygen can be delivered to the circulation even if a person is apneic. This phenomenon (apneic oxygenation) is explained in the following.

With the onset of apnea, an underpressure develops in the airspace of the lungs, because more oxygen is absorbed than CO2 is released. With the airways closed or obstructed, this will lead to a gradual collapse of the lungs. However, if the airways are patent (open), any gas supplied to the upper airways will follow the pressure gradient and flow into the lungs to replace the oxygen consumed. If pure oxygen is supplied, this process will serve to replenish the oxygen stores in the lungs. The uptake of oxygen into the blood will then remain at the usual level and the normal functioning of the organs will not be affected.

However, no CO2 is removed during apnea. The partial pressure of CO2 in the airspace of the lungs will quickly equilibrate with that of the blood. As the blood is loaded with CO2 from the metabolism, more and more CO2 will accumulate and eventually displace oxygen and other gases from the airspace. CO2 will also accumulate in the tissues of the body, resulting in respiratory acidosis.

Under ideal conditions (i.e., if pure oxygen is breathed before onset of apnea to remove all nitrogen from the lungs, and pure oxygen is insufflated), apneic oxygenation could theoretically be sufficient to provide enough oxygen for survival of more than one hour's duration in a healthy adult. However, accumulation of carbon dioxide (described above) would remain the limiting factor.

Apneic oxygenation is more than a physiologic curiosity. It can be employed to provide a sufficient amount of oxygen in thoracic surgery when apnea cannot be avoided, and during manipulations of the airways such as bronchoscopy, intubation, and surgery of the upper airways. However, because of the limitations described above, apneic oxygenation is inferior to extracorporal circulation using a heart-lung machine and is therefore used only in emergencies and for short procedures.

References

  • J.F.Nunn; Applied Respiratory Physiology; Butterworth-Heinemann Ltd; ISBN 0-7506-1336-X (4th edition, 1993)

See also

External links



Source | Copyright
Webmasters: Add your website here:

Readers: Edit | Discuss Listings

Oceanic Dreams
Wolfgang Leander, photographer, has captured images using a single breath of air. [requires Flash]
http://www.oceanicdreams.com

Scott Campbell Photography on Breathold
Freediving photography from California, USA.
http://www.on1breath.com

Miami Freediving Club
Information on Miami's Freediving Club as well as local spearfishing tournaments.
http://miamifreediving.com/

Rhode Island Freediving Club
Find information on events, results, contacts, photos, and links.
http://www.rifreediving.com/

Underwater Society of America
The USOA was formed in 1959 by the existing skin-diving (freediving) councils. Events, sports, news, documents.
http://www.underwater-society.org/

DiveWest
Kurt Bickel personal website, humour, tips, stories and pictures.
http://www.2xtreme.net/~kbickel/2index.html

Glenn Venghaus, Netherlands freediver
Freediving information for the active and beginning apneist by Glenn Venghaus an international competitive freediver and static apnea national record older.
http://cgi.tachyon-consulting.nl/freediving/index.php

Umberto Pelizzari, The Official Site
Record holder Umberto Pelizzari shares his personnal viewpoint on freediving as well as biographical informations such as records and pictures.
http://www.umbertopelizzari.com/

Breath-Hold Diving Bibliography
Breath-Hold Diving Bibliography compiled By Larry "Harris" Taylor, Ph.D.
http://home.earthlink.net/~divegeeked/biblios/breath.htm

Mehgan Heaney-Grier
The Official Website
http://www.freediver.com/

Hvidovre Freediving Club (Copenhagen, Denmark)
Club information (contact, mission, location)
http://hfk.dk/english/

Freedive Vancouver
Vancouver freediving club dedicated to recreational and competitive freediving.
http://www.holdyourbreath.ca/

Freediving Team Ã…land
Freedivers training at Idrottsgården.
http://freediving-aland.propercomfy.co.uk/

Israel Freediving
General information on freediving courses, training, safety and spearfishing.
http://www.freediving.co.il

British Freediving Association
The BFA was set up in 1999 to promote freediving in the UK, and to encourage the safe practice of the sport. It is the UK representative of the International Association for the Development of Apnea (AIDA).
http://www.britishfreediving.org

Mandy-Rae Cruickshank
Champion freediver. Records she holds, upcoming events, photo gallery, and training regimen.
http://www.mandy-rae.com/

CMAS - Confederation Mondiale des Activities Subaquatiques
The World Underwater Federation. One of the oldest dive organisations in the world, and one that serves to coordinate standards among water sports and activities; including sub-diving, freediving and spearfishing.
http://www.cmas2000.org/

BlueWater Freedivers Publishing
Books, videos and pictorials on freediving and spearfishing.
http://www.freedive.net

Official discussion group of AIDA UK.
A general discussion forum for British freedivers.
http://groups.yahoo.com/group/AIDAUK/

Freediver
Official magazine to the Association International for the Development of Apnea. With equipment, buddy finder, course information and latest news.
http://www.freediver.co.uk/

Freediving
Information on freediving records and events, and a large listing of freediving sites.
http://www.geocities.com/~freediver/

Redefine Your Limits
Official website for Tanya Streeter, a world champion freediver.
http://www.redefineyourlimits.com/

METU Freediving Group
Established in 1992, the Middle East Technical University (METU) Freediving Group aims to promote apnea in Turkish waters. Find announcements, information on training, contacts and photos.
http://www.metu.edu.tr/home/wwwaida

Freediving Web Ring
Link list for freediving and spearfishing sites.
http://www.geocities.com/Pipeline/Reef/9148/web.html

Freediving Regulations and Education Entity (FREE)
Freediving courses from beginner to instructor, available in USA, Australia, Turkey and Italy.
http://www.divingfree.com/

Performance Freediving
Offers courses and clinics in Miami, Florida. Find history, news, and contacts.
http://www.performancefreediving.com/

Japan Apnea Society
Information and activities of this Japanese branch of A.I.D.A. In English and Japanese.
http://www3u.kagoya.net/%7Ejas-apnea/

The British Underwater Sports Association
BUSA was formed in 1998 to co-ordinate breath-holding sub-aqua sports in the UK. Contacts listing.
http://www.busa1.freeserve.co.uk/

Freediving South Africa
Freediving Rules and regulations for static apnea, dynamic, and constant weight freediving. Pictures and results of FSA league events. Also includes records, history, and related links.
http://www.freediving.co.za

Apnea Magazine
Italian e-zine devoted to freediving, spearfishing and underwater target shooting. Discover diver profiles, articles and discussion forums.
http://www.apneamagazine.com/eng

AIDA Sweden
Discover information on the sport, records, profiles of individual divers and photos.
http://www.freedive.nu/

Canadian Association of Freediving and Apnea
Information and activities of CAFA the first non-profit freediving association in Canada. In English and French.
http://www.freedivecanada.com/

The Freedivers Resource
Features news, images, training tips, FAQ, contacts, and forum.
http://freedivers.com/

Freediving.at
Features course information, events calendar, and news. [English and German]
http://www.freediving.at/

Martin Stepanek - World Freediving Champion
Homepage of a world champion in breath-hold diving.
http://www.martinstepanek.com

Deeper Blue
Interactive content for Scuba Diving, Freediving and Travel.
http://www.deeperblue.net

Apnea Planet
Features news, photos, articles and links to related sites.
http://www.apneaplanet.com/

No Tanks!
Freediving and snorkeling by Len (Leonard) White. Underwater photographs and information.
http://www.stormpages.com/notanks/index.html

Florida Skin Diving Association
Find information on tournaments, events, links, and contacts for the organization.
http://www.fsda-wcc.com

Jacques Mayol
Renowned freediver and author of "Homo Delphinus", about man's spiritual connection to the sea. It was an immediate success in Italy, France, Russia and Japan, where it has become a best seller and is considered to be the Bible for all breath-hold divers. The movie "The Big Blue" was inspired by him.
http://www.thejacquesmayol.com

World Wide Freedivingspots Spots
Database offering information on locations. Find news and contacts.
http://www.freedivingspots.net/

The Zen of Freediving
Article describes aspects of the activity and includes photos.
http://www.sfdj.com/sand/freedive.html

International Association of Free Divers
IAFD was set up in 1997 to promote the sport of Free Diving and to support and assist the Free Diving community.
http://www.iafdusa.com/

Sebakfins
Sebakfins website, performance fin manufacturer
http://www.sebakfins.com

AIDA - International Association for the Development of Freediving
AIDA is a worldwide freediving Federation manages and overviews freediving records. It also sets education and safety standards.
http://www.aida-international.org/

FreediveList
Features a bulletin board, FAQ about freediving, pictures and stories of the week, and general list information.
http://www.freediver.net/

Rene Potvin's Freediving Page
Freediving tips and resources.
http://freediving.netfirms.com

Patrick Musimu
Patrick Musimu, a Belgian competitor offers information on his records and freediving clinics.
http://www.patrickmusimu.com

Picasso America
Picasso american distributor's site including online shopping, news and information on events such as the Picasso Open.
http://www.picassoamerica.com

Jacques Mayol
Biographical information on Jacque Mayol as well as notes on his philosophy from an Okinawa tourism bureau.
http://www.summit-okinawa.gr.jp/tokusyu/jm1.htm

Hawaii Skin Diver Magazine
Sterling Hanapaa's stylish freediving and spearfishing magazine.
http://www.hawaiiskindiver.net/



Help build the largest human-edited directory on the web.
 Submit a Site - Open Directory Project (modified) - Become an Editor

Modified contents copyright 2008. All rights reserved.