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New Ideas on Narcosis

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In the first in a new series adapted from his latest book, Scuba Physiological – Think you know all about Scuba Medicine? Think Again! best-selling Author and Diving Professional Simon Pridmore delves into the subject of Nitrogen Narcosis… 

The chapters in Scuba Physiological were originally written by scientists in the field of decompression research as part of a three-year project called PHYPODE (Physiology of Decompression). My (self-appointed) task was to rewrite their sometimes-complex research in a form accessible to all divers.

The researchers raised some eye-opening thoughts on nitrogen narcosis, showing that it is something that most divers THINK they understand but few actually do.

What is Nitrogen Narcosis?

Nitrogen narcosis is a condition affecting the physical and mental state of people who breathe air or mixtures containing nitrogen (or other inert gases) at pressures greater than 3 to 4ATA. Conventional scuba diving theory holds that narcosis occurs when molecules of a narcotic gas expand the volume of a hydrophobic membrane – an idea referred to as the “lipid theory”. However, recent studies have discredited this concept and revealed that, in fact, nitrogen narcosis occurs via the production, release and uptake of some brain neurotransmitters.

Everyone is affected by narcosis to some extent when they dive deep. Responsiveness can differ from person to person, but it is commonly accepted that the effects begin around 30m (100ft), although some people may experience effects of narcosis from 21m (70ft). The signs and symptoms cover a wide range of severity, from mild performance impairment to hallucinations and general anaesthesia. The deeper you go, and the longer you stay, the more severe the symptoms become.

Nitrogen narcosis is a more serious concern than many divers believe. In order to operate effectively underwater, a diver has to master a considerable number of different skills that rely on manual dexterity, motor coordination and both short-term and long-term memory. These skills are essential to staying safe in situations where precise actions and accurate judgement are required. And these skills are the ones adversely affected by nitrogen narcosis.

‘Beware of distorted perception…’ Photo: William Bynum

What Causes Nitrogen Narcosis?

As the underwater environment in which divers operate is markedly different from the surface environment, it seems logical that environmental factors should influence performance and, over the years, the diving community has cited a number of these as contributing to the onset and severity of narcosis, albeit without much scientific evidence. For example, increased partial pressures of CO2 from hard work or heavy swimming are believed to enlarge cerebral vessels leading to a higher nitrogen presence in the brain. Other supposed environmental risk factors include alcohol use, being hungover, fatigue, anxiety or apprehension, the effects of motion sickness medication, rate of descent, task loading and time pressure stress.

From a scientific point of view, the evidence for most of this is not strong. Claims about whether something exacerbates or reduces narcosis have often been based on fuzzy criteria and this has led to divers being given some dubious advice. The science shows that all you can really be sure of is that ethanol exacerbates the signs and symptoms of narcosis and amphetamines alleviate them.

There are two ways to try and quantify the effects of nitrogen narcosis. The first is a behavioural approach, measuring task performance such as mental arithmetic, memory, reaction time and manual dexterity. Although these behavioural studies have confirmed progressive deterioration as the surrounding pressure increases, many of the tests are unreliable because motivation, experience and learning can influence the results.

The second approach relies on observing changes in objective, measurable neurological parameters, using electro-encephalographic (EEG) recordings and the like. Several recent such studies have been conducted. These were the first to measure the effects of nitrogen narcosis during an entire dive AND for a period of time after the diver surfaces. Based on lipid theory, diver-training programs have always advised divers that, in the event of nitrogen narcosis, all they have to do to make the effects go away is ascend to a shallower depth. One of the most remarkable findings from these studies was that, not only is this not the case, but that the actual cerebral impairment caused by nitrogen narcosis persists for at least 30 minutes after SURFACING. So don’t dive and drive: not immediately anyway.

The studies also provided significant evidence that, when objectively measured, nitrogen narcosis may be influenced simply by pressure and the gas being breathed. It seems that the environmental factors referred to above have little or no impact.

Adaptation or Tolerance?

The diving community generally believes that divers can adapt to the signs and symptoms of nitrogen narcosis. This belief is based on experiments that reported an initial deterioration in task performance followed by significant improvement. However, on the contrary, scientific tests have generally been unable to confirm any habituation and researchers have concluded that sport divers do not develop tolerance to nitrogen narcosis.

Instead, it is more likely to be the case that divers who perform the same tasks over and over again will gradually find them easier to do and this may lead them to feel that they have developed narcosis tolerance. They think that they are really adapting to narcosis but, in fact, they are just learning to cope with it. A good analogy is habitual drunks who learn to cope with their impaired reflexes, cognitive functions and motor skills. The problem is, of course, that even though they may be able to deal with things better, they are still just as drunk.

Take-home Messages

  • Nitrogen narcosis can impair a diver’s ability to function effectively or even survive.
  • Nitrogen narcosis alters the higher functions of the nervous system.
  • Cerebral impairment from nitrogen narcosis persists for at least 30 minutes after surfacing.
  • Divers cannot develop tolerance to nitrogen narcosis but they can learn to cope with it.
  • You may feel less “narked” when you ascend from depth but, objectively; you are still just as “narked”.

More background on this research and further new ideas on narcosis can be found in Simon’s book Scuba Physiological – Think You Know All About Scuba Medicine? Think Again! available as an e-book from Amazon stores worldwide. Find our more about Simon and his books at www.simonpridmore.com.

Simon Pridmore is the author of scuba diving books, travel books and, as you might expect, scuba diving travel books. Originally from the UK, Simon has lived in Asia for over 30 years. As well as his books and guides, Simon writes regular columns for a number of magazines. He and his wife Sofie currently live in Bali, Indonesia but spend a lot of time exploring other places trying (but failing so far) to find a cure for their itchy feet. Simon's latest book - Scuba Exceptional – Become the Best Diver You Can Be - the follow-up to his best-selling Scuba Confidential, is available now in paperback and e-book versions from Amazon stores worldwide. Find out more about Simon and his books on www.simonpridmore.com

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Four opportunities to go pro in 2024 with Dive Friends Bonaire

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Dive Friends teaches the Instructor Development Course (IDC) several times a year to students who are eager to share their passion for diving with the world.

Dive Friends is known for the personal approach throughout the course. Their in-house course director will lead the students through every essential step, mentoring them to achieve their fullest potential as a dive instructor.

Applications for the following IDC start dates are now open:

  • 12 April
  • 5 July,
  • 20 September
  • 29 November

Partnership with Casita Palma

If the student opts for the IDC-Deluxe or IDC-Supreme package, their accommodation will be arranged for them at Casita Palma. This small and quiet resort is within walking distance from Dive Friends Bonaire’s main dive shop location and has everything you need to relax after an intense day of IDC training. Breakfast is included, so the student will always be fuelled and ready for their day.

Contact Dive Friends Bonaire’s Course Director Eddy for more information: coursedirector@divefriendsbonaire.com.

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Scubility: Achieving Success through Adaptability

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Introduction to Scubility

Being a scuba diving professional, I am always fascinated by the beauty of the underwater world, filled with colorful coral and a variety of marine species. Every dive site around the world has something unique to offer, attracting the diving community to immerse themselves time and time again. The feeling of being underwater is a unique experience, akin to being in space, where you can escape Earth’s gravity to enjoy the freedom of movement. However, water sports are often believed to be accessible only to those with good physical strength, leaving others to only dream of being there.

The Genesis of Scubility

Scubility was developed as a way to help people with disabilities experience the magic of scuba diving or snorkeling. A few years back we became involved in the SDI Scubility program as a way to use our diving experience and knowledge to bring disabled people beneath the ocean. To empower them with a feeling where they can forget their disability and limitations. The image of a Wheelchair Hero from the movie ‘AVATAR’, who could walk and run only in dreams, was the first seed of the idea for a local Scubility program.

scubility

Launching the Scubility Course

Since 2014, my friend has dedicated himself to helping disabled people. Knowing that I am an SDI/TDI Instructor Trainer, he called upon me to help bring them into the world of scuba diving. Captivated by this idea, I decided to offer a special diving course adapted for disabled people: the SDI Scubility Course. The sole purpose was to bring happiness and a feeling of belonging back to our precious disabled students, by giving them an immersive experience under the sea. Perhaps, the mother ocean has a way of treating us all equally, to rebuild confidence and give hope of being alive.

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Adapting Diving for All Abilities

Initially, most Scubility divers in our programs were wheelchair users. The main challenge was to design a unique technique suitable for each Scubility diver, based on their limitations. To do so, we set up a protocol keeping in mind all the scenarios that could arise during diving, starting from boarding the boat, to diving, and the communication signals during the dive. Training was also provided to volunteer participants, mostly instructors and assistant divers.

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The Scubility Program in Action

In the last four events, we have enrolled many Scubility divers in the program. We also have a team of trained instructors and assistants; without them, this wouldn’t be possible. The main objective was to make safe and comfortable diving experiences for Scubility students. In fact, in the last Scubility program, which concluded in March 2023, we included a blind diver along with six other Scubility divers. We also had 8 instructors and more than 10 assistant participants to make this possible.

scubility

The main challenge for blind divers is to set up a communication signal. So, I designed a unique ‘touch signal’ for blind students where they just need to touch an arm to convey a message. For example, when an instructor touches your arm twice, it means he is asking, “Are you okay?”. In case of any emergency during the dive, the blind diver just needs to squeeze the arm of the instructor to get his attention to solve the problem. For each Scubility diver, there were at least two personnel, an instructor, and an assistant, assigned.

Impact and Emotions of Scubility

The most satisfying experience of this program was to see Scubility divers happy, with emotional, teary eyes. I could imagine that probably for the first time, or perhaps the only time, some of them could walk, stand, and move again underwater without a wheelchair, feeling alive again. Seeing a courageous Scubility diver overcoming all challenges and obstacles to make it possible definitely inspires me to organize more events like this.

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“Scuba Diving for All” Event

The biggest local Scubility program, named “Scuba Diving for All,” was organized in Khao Lak, Phang-nga Province, south of Thailand, from October 30 to November 5, 2018. We invited international Scubility participant divers for this event. Leading up to this program, we put in lots of effort, preparing hotels and resorts in a friendly design, making sure of choosing good dive sites, and above all, to bring a smile to our precious Scubility students.

scubility

I hope that this endeavor will serve as an inspiration for people worldwide to achieve what may seem impossible, while also raising awareness about the importance of charity and kindness in our society. I look forward to welcoming you soon to our joyful underwater realm.

As an SDI TDI & Scubility IT, Dan Phutthakhun Prungkananon, owner of All Star Diving Academy located in Thailand, has a deep-rooted passion for ensuring safety and fun in the water. Keep up with Dan and the All Star Diving Academy via Instagram  or Facebook and by checking out their Dive Center Facebook.

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