CNS Oxygen Toxicity - Richard Vann PhD

I posted a summary on Nitrogen and Oxygen Narcosis a couple days ago. The summary states that Oxygen is 0,26 as toxic as Nitrogen and that the major concern regarding O2 and depth is actually Oxygen Toxicity. Here is a short video from the DAN Video Guy on YouTube that covers just that. It is also an excerpt from DAN's 2008 Technical Diving Conference.


From Rec to Tec: Equipment

I spent the weekend teaching some courses recreational diving courses, mainly rescue divers. One of my students told me: "Wow! That is a cool BCD you've got". Actually that was not a BCD but a simple harness with a single cylinder wing and adapter and a cheap backplate... Ok, I know my personal gear is not special or cool but I found very interesting the fact that people actually find tech diving equipment "cool". Basically this is what I've got:

The traditional tec BC is a metal backplate, an air cell — also called a wing — and a harness made from 2-inch webbing. This configuration is still preferred by many techies, but adjustable shoulders with quick-release buckles and integrated weight systems are now common on modern tec rigs. There are even soft backpack designs built to carry the load while providing more comfort.

In the process to start a technical diving community here we've had the need to contact new equipment dealers. Mainly Dive Rite and Hollis Gear for Open Circuit. I have imported some and will continue to bring more. If you are interested in buying a BCD that is good for tec and rec or just if you find tech diving equipment cool I suggest you take a look at these options. Al can be sold in Ecuador and the rest of the world trough us as an authorized dealer. I suggest you take a look at these few options.

Dive Rite Nomad EXP

While this rig is tailor-fit for side-mount configurations and rebreathers, it works just fine with a set of doubles or a single cylinder. Our test unit came with a 60-pound-lift single bladder and the semirigid backpack extends downward to include a butt plate that offers attachment points for side-mount cylinders and a crotch strap. $699

Designed as the ultimate sport diving BC, the ATS leaves nothing to be desired. Uniquely fitted with technical innovations that allow for just about any accessory to be incorporated, this BC can be customized for any recreational / tech cross-over diver’s needs. Providing complete comfort with its contoured harness, integrated weight system and streamlined bladder, the ATS makes every dive effortless. $640.55


A better understanding of narcosis

The following text is an abstract from the chapter "Nitrogen narcosis, oxygen narcosis and the high pressure nervous syndrome" in the Conference Technical diving: Proceedings of the Divers Alert Network. January 18-19 2008. All the material writen below comes from that document and is under the speaker's authorship. My intention with this abstract is to summarize the some of the information contained in such paper and to allow a better comprenhension of narcosis. Source is:

Have fun!
Jorge A. Mahauad

Reading your way through a better understanding of narcosis.


The depth-dependent effect of nitrogen narcosis on psychometric performance was well illustrated by Shilling and Willgrube (1937). They noted the greatest severity immediately on reaching depth and that rapid compression potentiated the narcosis. Acclimatized subjects showed some improvement.

Case and Haldane found that at 250 fsw manual skills showed little deterioration. At 300 fsw, however, the narcosis was severe with marked impairment of practical ability and judgment. Manual dexterity was affected to a much less degree than mental ability. Orders were recognized but ignored; there was a sense of impending loss of consciousness, euphoria and dizziness, manic or depressive states, catalepsy and a disorganization of the sense of time.

There is no question that there is an individual susceptibility to the effects of nitrogen narcosis. This may be due to individual accommodation or “learning to cope” with a reduction in anxiety and recognition by the individual of his own signs and symptoms. Thus highly trained and experienced deep divers may be able to function much more effectively at depths which would incapacitate less experienced divers.

Rate of Compression or Descent

It is widely held that rapid compression potentiates nitrogen narcosis. The effect is believed due to an increase in alveolar and cerebral carbon dioxide. Carbon dioxide increase is reputed to increase susceptibility to nitrogen narcosis, oxygen toxicity and decompression sickness. 

In regard to carbon dioxide, Case and Haldane noted this as early as 1941 and reported that the combined effects of nitrogen and carbon dioxide in studies at 300 fsw with inspired CO2 percentages were much more severe than either gas alone.

Another somewhat hidden effect of CO2 is the enhancement of the effects of nitrogen narcosis by exercise or work during diving as shown again by the work of Adolfson. This indicated significant increases in decrements of psychometric tests in working divers compared to resting divers at 100, 200 and 300 fsw.

Oxygen Narcosis

Since technical diving involves use of nitrox and other mixed gases, there is considerable interest, if not controversy, on whether oxygen is a narcotic. Oxygen is different from the inert gases as it is metabolized in the body. Nevertheless, oxygen narcosis has indeed been reported in humans and animals.

In a human study oxygen was found to be only 0.26 as potent as nitrogen. The lower effect is no doubt due to its being metabolized and much lower levels actually occurring in the brain compared to the lungs.

No significant differences were found between nitrox and air. This in spite of many claims by divers breathing nitrox that they feel less narcosis – a possible placebo effect.

So in conclusion, in regard to oxygen narcosis, yes, oxygen can exert a narcotic effect, but it is less than predicted by its lipid solubility, almost certainly because oxygen is metabolized and tissue PO2 does not equilibrate with the PO2 in the lungs at the oxygen pressures that can be safely used in diving. Thus, in practical terms, oxygen narcosis is much less of a problem for technical diving than would arise from the use of nitrogen at significant depths. To overcome the potential for nitrogen narcosis, deep divers do use oxygen-helium mixtures as an alternative. However, this then introduces the problem of the high pressure nervous syndrome

Mechanisms of Nitrogen Narcosis

Briefly, it is considered to be similar to general anesthesia by gaseous anesthetics. This is based on the Meyer-Overton hypothesis “All gaseous or volatile substances induce narcosis if they penetrate the cell lipids in a definite molar concentration”.

In this regard there is still a strong relationship between solubility in lipids (fat) and narcotic potency. This was later confirmed in mice, newts and isolated nerves. This led Keith Miller at Harvard to propose the “Critical Volume Theory,” i.e., “Anesthetics expand a critical hydrophobic molecular site and pressure contracts this.” 

In simple terms, a “critical hydrophobic molecular site” represents structures in cell membranes that are important for conduction of the nerve impulses upon which normal function of our nervous system depends.
If these structures are physically distorted by absorption of large numbers of gas molecules, then conduction of nerve impulses can be impeded, manifesting as the cognitive impairment we call narcosis. This distortion can be reversed, i.e. the membrane structures can be returned to their original size or configuration by the application of high pressures; hence the fascinating phenomenon of “pressure reversal.”

Interestingly, this theory also implies that the application of pressure in the absence of membrane expansion by a narcotic gas would compress those same important membrane structures below their normal size or configuration, once again producing an interruption of normal function that is usually called HPNS.

Perhaps all that can be said is that at 100 fsw the narcosis is minimal, but becomes progressively worse with increasing depth and by 200 fsw can be a real issue as regards safety. In practice, virtually all of the technical diving training agencies encourage the use of helium mixtures for dives beyond 150 feet for making narcosis manageable.

ISO Standard for Rebreathers is shaping... have your say!

A new standard for rebreather manufacturing is being revised at this time. the prEN14143:2010 will shape rebreathers in the years to come. I suggest you take a look at it if you dive rebreathers or if you are considering it.

Gian A. Ameri and Rebreather Saftey DAN Europe are in a process to gather comments and information regarding the comments and reviwes of the standard. A letter signed by them follows:


Dear fellow diver,

As you may be aware, the rebreather dive industry has proposed a new rebreather safety standard “prEN14143:2010” and this will affect all current and future generations of rebreather divers.
The standard has been part of public consultation in Europe and anyone can submit comments and proposals to contribute to the creation of this new standard.
The deadline for submission of comments and proposals is 31 May 2010.
If you have not already done so, please consider contributing to the creation of this new standard and submit your comments and proposals to your national representative (called “Member Body”) of which you can find details including email address here 
You will need to use the attached blank template to submit your comments and proposals. Any question you may have or assistance you may require for your submission, please feel free to email me. You can find further details on the DAN webpage by clicking this link.

I enclose the comments and proposals I have submitted to date. All the documents I reference in the comments and proposals can be downloaded here: (login with username: rebreather and the password: safety1st ).
Please contribute and ask your friends to contribute to the creation of this new standard for all the divers and friends we have lost to date and the future generations of rebreather divers to come.

Dive safe!

Best regards,

Gian A. Ameri
Email gian@gian.ameri.name



Galapagos Listings...

The Galapagos Islands have been listed in number of diving blogs this week as a "must see / top destination" for SCUBA Diving. dailyscubadiving.com lists it as number 7 in their list and thedivingblog.com has also listed the islands in their "top five places to dive before I die" post. As I reported earlier this year SCUBA Diving Magazine ranked the Galapagos as their number one place in the world for big encounters.   

Some might say that this is not new(s). The Islands have been in the Top 10 lists for many years now. On the other hand, new operation permits are being issued at this time in the Galapagos Marine Reserve. The main focus of these permits (both commercially and economically) is actually SCUBA Diving.

There has been A LOT of speculation, information and misinformation on this matter but one thing is for certain: Soon more boats (both liveaboards and day trips) will be available in the islands.

I received a comment from Mike yesterday in this blog. Apparently, my new friend is promoting a site owned by Surtrek, one of the many tour operators that sell trips to the islands. I published his comment anyway even though I clearly understand that what he intends is to publicize his site and not to share anything valuable in mine. Why? Because getting this is kind of inputs is just inevitable. On the other hand, I would like to suggest some techniques for making the right decision if you are going to dive in the Galapagos Islands.

There is A LOT on information on currents, conditions, the dive profiles, liveaboard vs day trip all over the internet so I will not get into that. All the aspects stated before are very important in making an informed decision for your personal safety. Please inform yourself properly.

There is also a great deal of information regarding tours and trips. My main suggestion here is: Do not believe in everything you read. I think that the best way to make an informed decision in this matter is to go over the forums (scubaboard.com has a lot of information) and find real diver reviews. Many tour operators have their own dedicated marketing people posting and creating threads about their own. I understand this technique is called “sock puppets” and it is prohibited in many forums but it happens anyway.

Real divers are the best way to get trust worthy information. How do you separate the good from the bugged? Just take some time to investigate the profile of the user posting. Another handy suggestion would be to find out who the owner of the yacht or boat really is.

As part of the managing staff of a tour company with more than 40 years in the market I know that many internet sites and tour sellers don’t own the boats that they actually sell; therefore they will sell anything as long as it is profitable. In addition, some of the boats are not operating anymore and others have been blueprints for many years. Here in the Galapagos the reputation of the actual owner of the dive operation will tell you many things. Find that out.

The Galapagos Islands are strictly regulated. Even with these regulations some people find the way to get around the norm in order to make a product or service more appealing. Please find out the regulations and restrictions for the type of trip you are planning and follow those. There are risks involved when you purchase a “great deal” from someone who is avoiding the law; moreover, it does no good at all to the Islands. Be a responsible traveler, use only authorized vessels and recognized tour operators that are reputable.

Probably a few of my fellow Galapagans (or wanna be’s) will find my post a bit disturbing. It can be, depends on who they are and how they handle these things; others, hopefully most of them, will applaud. On the other hand, I feel that my responsibility towards conservation, responsible travel and regulation enforcement is greater than the sympathy I could gain or lose by making a post like this.

Get informed, get ready and have a great trip. If you are interested in Advanced Diving please do not hesitate to contact me. 

Jorge A. Mahauad 


The Revolution of Science Through SCUBA

The Revolution of Science Through SCUBA, a symposium “to celebrate the scientific contributions and value of scuba as research methodology,” is webcasting live since yesterday. The agenda is really impressive – it’s pretty much a who’s who in SCUBA-related underwater research.

One of the highlight in the conference is Jon Witman, who dives on rock walls in the Galapagos to understand how large-scale oceanography affects the food web.

You can watch the live stream at the Smithsonian Institution's site. At the moment we are "on break". The conference will continue at 1 ET.

Immersed Senses

This device has caused some buzz in the underwater community. Some say immersed Senses is the future of underwater diving and exploration. Improving the limitations of current scuba diving system, designer Adam Wendel has come up with a futuristic device named the “Immersed Senses” that changes the way the diver sees, hears, and breathes underwater, allowing them to become a part of their surrounding environment. 

Immersed Senses operates by a battery that utilizes a centrifuge mechanism to pull oxygen from seawater that begins the electrolysis reaction. Saltwater is extracted into the bottom reservoir that reacts with hydrogen gas. The saltwater is then charged by a positive and negative anode/cathode that generates breathable oxygen. Two internal devices help to circulate the oxygen to the diver’s mouth and nose.

Featuring a LED flashlight to let the diver to observe the dark depths of the ocean, the mask also includes a large OLED glass display to offer a panoramic view of the surroundings. The OLED enclosed helmet also allows the extracted oxygen to flow freely throughout the helmet, as if you are breathing on land without any breathing apparatus.

Read more at: The Design Blog


IDC Mayo 2010

He estado haciendo una pequeña edición de lo que fue el IDC con Exploramar Diving. Pienso hacer algunas partes, no sé cuántas todavía, si embargo aquí están las presentaciones de los instructores que participamos en el proceso de formación y de los candidatos.

Espero poder poner algo más pronto. Hay que encontrar un poco de tiempo para editar...

Jorge A. Mahauad


Brigitte Lenoir dies in Dahab

40 year old Swiss technical diver Brigitte Lenoir died in Dahab (Red Sea) on Friday. Brigitte was training aiming at breaking the female's world record for deep diving this August.

Brigitte died at -147 meters, on ascending from -200 meters. According to Jean-Luc Morier, a friend, the accident happened due to technical problems (a valve that injects pure oxygen through the rebreather) which lead to hyperoxic conditions in the breathing loop. Soon oxygen seizures occurred and lead to convulsions and death by drowning. 

The body was not been retrieved. She was accompanied by Pascal Barnabé, the world record holder of deep diving. He couldn't do anything to rescue her. Maximum security measures were taken for the dive's preparation. Preparation took place for 8 to 9 months. When the accident took place, Pascal Barnabé in addition to 10 other divers were spread on the descent line between -70 meters and the surface. Nearly 100 tanks were spread on the rope to a depth of -160 meters.

On April 12th, Brigitte did a -154 meters dive in Lake Geneva and established a new record for deep diving in this lake located close to Saint Gingolph . She aimed at doing 230 meters in Egypt in August.

A religious ceremony will take place this Wednesday at the Catholic church of Monthey. 


The new underwater channel is here!

World-renowned oceanographer Sylvia Earle is collaborating with UWC on various projects. Called "Her Deepness" by the New York Times, "Living Legend" by the Library of Congress, and the first "Hero for the Planet by Time Magazine". Here is here invitation to join the Underwater Channel


Tec Rec Ecuador going mobile with Mobify

I have set up a mobile friendly view of my blog using mobify.com this is a free (or paid) service to make sites just that: mobile friendly. 

From now on when you access this blog using a mobile device you will have a mobile friendly view. If you feel like it, you can also bookmark this link in your mobile device.
Enjoy it, I will :)
Jorge A. Mahauad

IDC Life!!

I have been a bit away from blogging this week. 
Why? IDC life.

For those of you who are PADI Instructors, you know what I mean!

I am currently working in association with PADI CD Michel Guerrero and PADI IDCS Janko Mesec from Exploramar Diving in an Instructor Development Course. At this time, his dive center is the only 5 star IDC in the region. We have been working with our 5 candidates (Andrés, Daniel, Eduardo, José and Paulo) for a while now.

We spent the week of April 26 in the IDC prep module and EFR Instructor Course. The IDC program started on May 3. We have been working hard for a few days now; we are half way through the IDC and things are looking good. The students are performing very well underwater; we had only 4 and 5’s today in the skill evaluation on the pool. Confined water presentations are going very good and they have their first prescriptive teaching presentation tomorrow. On May 12 we will travel to the coast to finish the Open Water section of the IDC and the IE will be held on May 15 and 16.

Here are a few pictures from today’s confined water session. The photos were taken by Paulo, one of our candidates who currently work for Scuba Iguana in the Galapagos. I will post more about this latter this month. I am working on a video for the course but that will take some time to edit.

From left to right: Andrés, José, Paulo, Daniel and Eduardo. IDC participants.
Candidates having fun underwater after the session.

PADI Course Director Michel Guerrero and Daniel Sornoza (Candidate)

PADI IDC Staff Janko Mesec evaluating a 5 point descent performed by José García (Candidate)

Diving is becoming a family activity very quick. Eduardo, one of the candidates is my brother; I am happy to have him here.

Eduardo being evaluated on a fin pivot

I think we will be teaching some other close relatives of mine soon. My cousin Fabián completed his PADI Divemaster a couple years ago. Other cousin of mine, Charles, is half way through his DM course and my brother Javier and my other cousin Felipe are newly certified Rescue Divers.

We will make a very good team of multilevel instructors and divemasters very soon. So many IDC’s to come!
Jorge A. Mahauad
PADI Master Instructor


Sea Shepherd Galapagos Presents Shark Awareness Pack

With a full page article in the local newspaper el Colono, Sea Shepherd Galapagos has started a project to raise awareness among the inhabitants of the Galapagos regarding the protection of sharks.

Worldwide sharks are being exterminated at an alarming rate and it’s time to use whatever means available to halt the senseless massacre. Next to law enforcement, education can give a well-needed contribution on this conservation issue.

In the coming six months, Sea Shepherd Galapagos will be posting advertisements in the local newspaper. They will also have messages broadcasted daily on the local radio station containing many interesting facts about sharks. At the same time, they will inform about the devastating impact shark finning has on shark populations, and just how cruel this practice is.

The information is primarily aimed to inform the children of Galapagos but through them there is the opportunity to reach their families as well. Ideally, the ads will be collected and discussed at the children’s homes with friends and family.

Some of the ads invite the readers to participate, and for this there is now an information board outside the Sea Shepherd Galapagos office where children can post their drawings and answers to the questions asked.

At the end of the six months all the information will be combined in a teacher’s guidebook, which will be offered to the schools for educational purposes in the years to come.

This project was made possible thanks to the generous support of LUSH.


Technical Diving Courses and Equipment

Last Monday I received my first shipping of technical diving equipment. I have been a bit busy working on some ideas and teaching in a prep course for an IDC. On the few free moments I’ve had, I have been configuring and rigging the new technical diving equipment.

Yesterday, after a meeting to discuss new entrepreneurships in technical and recreational diving in Ecuador and the Galapagos Islands, I had the chance to make a few pictures of the rigs and to record a few tips on how to configure stages.

If you are interested in learning technical diving you can obtain further information here. I will be posting more on this soon…

Jorge A. Mahauad