Dive Training Blogs
New Ideas on Narcosis
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.
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.
Blogs
Four opportunities to go pro in 2024 with Dive Friends Bonaire
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.
Blogs
Scubility: Achieving Success through Adaptability
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.
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.
“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.
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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