This is Your Brain… on Scuba Diving Our brain. A collection of cells. Basic chemicals. Basic molecular structure. The brain is made up of simple neurons which combined make up neural networks. These extremely complex networks make us who we are. The complexity of the brain and its raw power are awe inspiring. Just think about the fact that right now, this very moment, a bunch of cells and chemicals are arranged in just the perfect order so that you can read this. Yes, tiny microscopic neurons, with only 3 structural features that make them up, are somehow reading this. Those simple nerve cells are our only way of perceiving the physical world around us. Sometimes our perception is not what we think it is. A unique phenomenon that can occur in our brain are hallucinations. We do not know in some cases how or why they are caused but we do know that they have occurred throughout all of human history from accounts in art, music, and literature. Many tales have been told about hallucinations especially from sailors at sea.
The lack of stimuli in the open ocean and psychological torment of being confined on ships for long periods of time have often prompted these hallucinations at sea from everything to fake islands to sea monsters. Many of these tales have been documented or portrayed in literature throughout history.. One of these stories is a poem titled The Rime of the Ancient Mariner Written by Samuel Taylor Coleridge. The poem is set outside a wedding where an old man who identifies himself as a old sailor tells a guest on his way to th nearby wedding of a voyage he has had and the ordeal he went through. The voyage takes place in the southern seas, as can be inferred from his description of snow, ice and also the albatross, as they populate the most southern quarter of the hemisphere. After killing the albatross he realizes something is amiss as the fortune of the crew turns. Following this timeline conditions on the boat deteriorate rapidly and the mariner begins to discuss the supernatural aspects of the voyage. He tells of seeing a ghost ship, the spiritual beings of death and life-in-death, crew members inexplicably dying and resurrecting around him, and a multitude of supernatural and biblical encounters. Not only is the surface of the ocean dangerous but the subsurface of the ocean is a even more extreme environment. Humans are not able to naturally survive in these harsh conditions, not only due to the lack of respiratory gas but also other factors such as pressure and temperature.
The only method for humans to visit this mysterious part of the world with no physical protective infrastructure such as a semi-submersible or submersible vessel is through scuba diving. Scuba diving itself creates many neurological risks such as increased psychological stress, hazardous chemical reactions, physical neurological trauma. The range of symptoms that can arise from numerous conditions in diving accidents is astonishing both physically and psychologically. The evolution of diving over the years has made diving safer but more accessible to the general public, leading to more divers and hence more dive accidents. Scuba stands for self contained breathing apparatus. Before the 1940s, diving was closed circuit and tethered meaning that usually air was supplied by a hose connected to an air source on the surface. This requirement of surface supported and its associated cost prohibited the recreational use of diving which created a market only available to the military or commercial operations. The These primitive diving gear usually consisted of a helmet that enclosed the divers entire head, commonly seen in media for divers in the late 19th and early 20th century (Figure 1).
The air that was delivered to the system was normal atmospheric air that was forced at low pressures from the surface to the diver. The need of surface support severely limited the divers maneuverability due to the surface hose. The surface hose also posed an extreme safety risk due to the fact that if the cord was block or severed, the diver has no redundant life support and depending on the depth of the dive, faced certain death. Even when Scuba Diving was invented, it was dangerous and experimental. It was not considered a recreational activity until the 70s, nearly 30 years after it’s invention. Diving technology has advanced rapidly due to the volume of recreational divers increasing over the years. Everything from diving masks to underwater navigation have advanced tremendously. Today, scuba diving gear (Figure 2) is highly redundant and technologically advanced, all self contained and relatively easy and simple to operate as well as inexpensive compared to earlier diving gear. Like diving, sailing was a daunting and unknowing task until recently where it’s become a pleasure hobby almost anyone can do where in earlier centuries only highly skilled sailors could take the journeys out of the high seas. Navigation relied solely on magnetic headings and astronomy. Ships were made out of wooden planks and ships limited by their sails. In The Rime of the Ancient Mariner, we see how vulnerable older ships were. “The fair breeze blew, the sails dropt down. ‘Twas as sad as could be” (Coleridge 103-104). Even in early sailing like diving, there was a fatal lack of redundancy. Once the wind dies down, the sails fail to provide energy for the ship to move and the sailors have no ability to propel a large ship. This problem persisted until the early 19th century with the invention of the steam engine in which ships could provide their own propulsion Significantly more research is needed in the both the effects of scuba diving on the physical human anatomy and especially of the human brain. In terms of medical history, scuba diving is a relatively new event, due to the current process and the amount of time medical research takes, most of the research conducted has been by governments who have the ability to invest capital into research projects. Now that recreational has taken off with over 6 million certified divers not including the possible hundreds of thousands non certified divers, researchers are just beginning to uncover the risks scuba diving poses.
Researchers in a article called Brain Damage in Divers, published in the British Medical Journal, found in normal recreational divers signs of brain lesions but were hesitant to declare them as such to be conservative in the study being conducted. They state that “None the less, this report will cause concern among both professional and recreational divers. Further cross sectional studies will add little more to our knowledge” (Wilmshurst 1761). The fact that researches themselves admit to the lack of knowledge they have on the correlation between abnormalities in the brain to normal recreational diving is quite disturbing. According to the Insurance Institute for Highway Safety (IIHS) “fatal motor vehicle crashes in the United States in 2017… resulted in 11.4 deaths per 100,000 people” (Insurance Institute for Highway Safety). Compared to scuba diving, in a report titled Annual Fatality Rates and Associated Risk Factors for Recreational Scuba Diving for the Divers Alert Network (DAN) “The annual fatality rate (AFR) of 16.4 per 100,000 insured Divers” (Denoble 73). When scaling the statistic divers have approximately 44% more risk than drivers to experience a fatal accident. There are many accounts of sailors having psychotic breakdowns while serving aboard ships. These accounts documented before modern psychology, were usually attributed to a multitude of mythological causes such as a curses, ghost ships, mermaids, sea monsters and more tales. Many of these phenomenon experienced by early sailors have easy explanation in modern psychology and neurology. Anyone of these accounts can be easily attributed to hallucinations.
In Jeanie Watson’s analysis of the Rime of the Ancient Mariner on the poem and it’s relation to fantasy, she references the encounter with the two polar voices the mariner hears after regaining consciousness, and states that “The mariner is afraid that that sight may be a dream, but he never questions the Reality of the world of the voyage.” (Watson 166). This alludes to the fact that during the course of the entire poem that he never actually considers the fact that the reality he is experiencing may not even exist. Hallucinations are extremely powerful, in a sense they are a reality to the one experiencing the hallucinations. In scuba diving hallucinations can be extremely hazardous because of the fact that they can disoriented and even psychological break down the diver when there is no differences between reality and the hallucination. Lack of stimuli in the ocean and being confined to a ship creates a breeding ground for psychological episodes. Claustrophobic divers may experience episodes due to the realization of air is only inside the air system and there is no air surrounding them, that air is all that’s keeping the diver there. In regards to psychiatric disorders, Attention Deficit Disorder (ADD), is especially concern for divers. Diving requires an intense amount of concentration monitoring, depth, remaining air, planning, navigation, and being cautious of the environment around the diver. Another factor that has to be considered is medication. In CNS Considerations in Scuba Diving by Dr. Hugh Greer he states that “No testing has ever been done to determine interactions between high partial pressures of nitrogen and the medications used to treat attention deficit disorder. Two drugs currently in use are Ritalin(r) (methphenidate) and Dexedrine(r) (dextroamphetamine). Both are heavy-duty stimulants that leave most adults ‘wired.’ (Greer) The unknown reactions of medication with the diving environment should be taken serious as these medications directly affect the nervous system which already is under the effects from normal diving. Failure to constantly monitor these psychiatric and psychological factors can lead to more serious injuries or death. Divers have to be in top mental shape in order to dive safely. Nitrogen Narcosis is a specific type of inert gas narcosis. Inert gas narcosis is caused by breathing certain gases under pressure. Gas narcosis creates a unique psychomotor impairment which has similarities with alcohol intoxication, cannabis and other benzodiazepine drugs. This can produce a euphoric dream like state. These euphoric episodes can be quite deadly due to the fact that it can distract the diver from essential tasks and awareness. Most recreational scuba tanks are filled with compressed with normal atmospheric air which are comprised of about 21% Oxygen and 79% Nitrogen. A standard 80 cubic foot scuba tank is usually under 3000 pounds per of inch of pressure. In perspective, the pressure at sea level is a mere 14.7 pounds per inch. This means inside scuba tanks the air pressure is over 200 times normal atmospheric pressure. More research is needed to better understand the biochemistry behind gas narcosis. Researchers currently believe that the cause of narcosis has to do with the gas interaction with neurotransmitters. One hypothesis infers that the gas dissolves into the fatty lipids in neurotransmitters causing direct interference with chemical signals which can range from the gas blocking neurotransmitters as well as also altering the chemicals being transmitted. Although narcosis is difficult to prevent, there are few precautions divers can take. One such precaution includes limiting the maximum depth of the dive to 130 feet, which “is an appropriate limit for single-cylinder no-stop diving with air” this is because of the “short no-stop time you have [during the dive] plus the relatively quick consumption of your gas supply,” says Karl Shreeves, PADI’s technical development executive. “[130 feet] is also the depth by which almost all divers begin to find gas narcosis noticeable.”(Zunz). Another precaution to diving in shallower depths is the reduced severity of narcosis. It is ultimately up to the diver to know his or her limits. Many people would be surprised when they learn of the dangers that our respiratory lifeline, oxygen can pose. Oxygen toxicity is mainly a concern for divers more than any other demographic. Breathing oxygen at high partial pressures, higher than normal atmospheric pressure are at risk for oxygen toxicity.
Symptoms relating to the Central Nervous System are particularly noticeable and are usually the first symptoms of oxygen toxicity. They include tinnitus (ringing of the ears) tunnel vision, behavioral changes such as irritability, stress, anxiety, and euphoria, inner ear coordination such as vertigo,and tonic-clonic seizures. “In recreational the most likely cause of oxygen toxicity is diving with oxygen enriched air (i.e., Nitrox). Nitrox is a breathing mixture that contains more than 21 percent oxygen (usually 32 to 36 percent), and allows extended bottom time” (Newton) Nitrox also allows oxygen toxicity to be more prominent at shallower depths. The best way to prevent oxygen toxicity is to know the early onset signs and symptoms. If divers are using Nitrox extreme caution should be used and recurrent training should be pursued. Barotrauma is any type of trauma caused by pressure. Because most diving accidents occur due to pressure difference, barotrauma is common in diving accidents as a primary condition or a subset condition. Barotrauma can occur in the ear, due failure to equalize pressure through “equalizing” (Figure 3) or blockage of the ear canal which prevents pressure equalization. Due to the reliance of the the inner ear, particularly the vestibular system, which gives us the sense of orientation and balance, any damage or interference caused by pressure is sent to the brain via the Vestibulocochlear nerve which can create a false sense of orientation, confusion, and vertigo.
Barotrauma can also occur in the pulmonary system where the lungs or alveoli are damaged by pressure which then reduces the flow of oxygen in the body, this creates a hypoxic state where mental judgement can be impaired and consciousness can be affected. The mariner in The Rime of the Ancient Mariner experiences this state, he recalls to the wedding guest It flung the blood into my head And I fell down in a swound How long in that same fit I lay, I have not to declare But ere my living life returned I heard my soul discerned Two voices in the air (Colderidge 391-396) The mariner says he entered a swound, which in modern terminology is fainting or lossing conscious. He has no recollection of the time that has passed and seems lost and as he regains consciousness and begins to hear voices in his head. Common fatal symptoms according to Catastrophic Injuries in Sports and Recreation : Causes and Prevention, “Severe complications of barotrauma can include pneumothorax and the development of arterial gas emboli. Pulmonary barotrauma (barotrauma to the lungs causing pulmonary embolism)” (Heinicke 196) Arterial gas emboli are a serious concern for the nervous system. Gas bubbles can travel through the arteries and into the brain (Figure 4) where they can cause blockage of the arteries restricting blood flow to the brain. This can produce similar neurologic symptoms as other conditions such as hypoxia, making a hard on site diagnosis.
Medical professional have to use imaging techniques such as Magnetic resonance imaging or X-ray to diagnose internal barotrauma and embolisms Proper medical treatment must be sought immediate to increase the chances of survival Hypoxia as a general definition is the lack of oxygen delivering to tissue. Hypoxia in the brain is a serious condition that has to be treated immediately to prevent brain damage or death. Symptoms vary but according to Neurology in Clinical Practice: Principles of Diagnosis and Management, the cause of hypoxia may originate from a number of events, such as “smoke or carbon monoxide inhalation, high altitude exposure, strangulation, anesthetic accidents, or poisoning.” In more severe cases of anoxia and hypoxia, symptoms my cause “stuporous or comatose”, in other words, the patient will be in a state of unconsciousness ranging anywhere from hours to days, weeks, or even months. Other documented symptoms include “seizures, myoclonic jerks (muscle spasms or twitches), and neck stiffness” (Newton). In scuba diving, hypoxia is extremely dangerous because the symptoms that have the ability to occur underwater can lead to immediate death, commonly by drowning. The certifying diving agencies require a diving physical which usually rules out many pre conditioned and susceptibility to hypoxia. However diving hypoxia can occur to any diver in cases where there are equipment malfunctions such or total exhaustion of air supply in a rapid manner. The most common and deadly condition that can be caused from scuba diving is Decompression Illness, commonly known as Decompression Sickness or “The Bends”. In the brain, nitrogen bubbles quickly expand due to the reduction of pressure, these nitrogen bubbles collect in the arteries and veins supplying the brain. This causes rupture and introduction of blood and fluid into the cranial cavities causing disruption to the brains homeostasis.
Decompression illness is also extremely deadly because in some cases symptoms can occur hours or days after the dive. Symptoms of Decompression Illness are physically extremely painful, such as “ limb pain, itching, and skin markings; nonspecific constitutional symptoms include headache, fatigue, malaise, nausea, vomiting and anorexia, enlarged and tender lymph nodes, vertigo and deafness, and cardiovascular or pulmonary compromise”(Prockop 531) Gas bubbles that end up in either the brain or spinal cord create unique neurologic problems “including weakness, loss of sensation, ataxia, vertigo, disturbance of consciousness, disturbance of vision and mentation” (Massey 550). On top of the severity of the symptoms, “Unless recompression is achieved promptly, the signs, including paralysis, are often permanent.” (Prockop 531). Decompression Illness late onset creates problems in the treatment because of the fact that recompression requires a hyperbaric chamber and there are around 300 chambers in the US but a few handful specializing in dive related treatment as a majority of chambers are used for primarily other treatments. Hyperbaric chambers replicate the pressure at depth and once the patient is at depth they are slowly depressurized to atmospheric pressure in order to slowly release the gas bubbles in the body. With millions of new divers each year, diving accidents will continue to be a issue for the dive and medical community. Neurology and oceanography are some of the most interesting and complex research being conducted currently. Scuba diving allows us to explore a entire new and alien world. As with all exploration, there are great unknowns and risks. Scuba diving in itself can be extremely deadly if techniques are improperly performed. The literal pressure you are under both physically and mentally is dangerous. Better and more training classroom time and dives should be implemented across all of the diving certifying agencies to prevent inexperienced and experienced divers from sustaining neurological damage. Our brain is everything we are, we need to know more about it’s comp lexities, which any data can help across the medical field from physical brain injuries to mental illness. In today’s society we need to know more about the brain in order to combat the exponential growth of neurological disorders.