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Inert gas narcosis refers to the mental and physical discomfort both objective and subjective, which results from inhaling gas mixtures containing particular types of inert gases (argon, helium, krypton, xenon and atmospheric nitrogen) under considerable pressure. It refers to the reversible shift in consciousness that results into states similar to those experienced from nitrous oxide inhalation or alcohol intoxication. Inert gas narcosis can occur during shallow dives; however, it becomes widespread at depths beyond 30 meters, which is approximately 100 feet. However, the depth of the dive varies according to the type of inert gas mixture used. Inert gas narcosis is mainly witnessed by commercial divers during deep sea diving. The gases are responsible for narcosis in deep diving include hydrogen, Helium and Nitrogen. Nitrogen is responsible for nitrogen narcosis, while Hydrogen and helium are responsible for hydrogen narcosis and helium narcosis respectively. Typically commercial divers work in pairs, one in the water surface tending at the equipment and the other under water.
Nitrogen narcosis was actually described as the "rapture of the deep" by Jacques Cousteau. Its exact physiological mechanisms are not well understood but research suggest that it occurs when nitrogen dissolves into the nerve membranes and into the blood stream causing subtle interruption in nerve transmissions. Research suggest that the signs and symptoms of narcosis may commence while an individual is breathing air during dives of up to 20 meters, but most of the symptoms are not noticeable. The effects of narcosis are very evident at 30 to 40 meters above sea level. At depths of over 91 meters, the effects are very adverse and may include stupefaction, impaired muscular activity and possible loss of consciousness, hallucinations or even death. Between the depths of 30m and 91 m, the consequences vary from one diver to the other and even between individual divers on different days. The signs of narcosis, especially nitrogen narcosis, are very similar to the effects of alcohol or anaesthetic gas. At great depths, inert gas narcosis can have very disastrous effects or may even lead to death. When deep diving, it is recommended that the divers descend at a very steady pace to prevent any sudden changes and unbalanced solution of the particular breathing gases in the blood.
Sedating drugs such as marijuana and alcohol should be avoided within 24 hours before diving because they have the potential of increasing the risk of nitrogen, helium or hydrogen narcosis. The effects of narcosis vary depending of the depth of the dive and the gases use for breathing. Nitrogen narcosis widely commences at 30 metres and the most evident signs and symptoms include light-headedness, euphoria, dizziness, mental stimulation associated with great confidence, lip trembling, peripheral numbness, hallucinations, disorientation, loss of balance, wooziness, fixation of ideas, impairment of complex reasoning, lowered reaction time, vertigo and psychomotor and intellectual decrements. Hydrogen narcosis commences at diving depths of up to 300 metres and is characterised by confusion, hallucination, disorientation, amnesia, hallucinations, agitation, mood disturbances, delirium and paranoid thoughts. Research suggest that the effects of helium narcosis start at approximately 400 metres and are often very different from the symptoms of nitrogen narcosis, both in their nature and their behaviour with time and are referred to as High Pressure Nervous Syndrome. Some of the notable symptoms of helium narcosis include course tremors especially of the hands which may improve after one or two hours, feelings of weakness, clumsiness, nausea and dizziness, prostration, Tremors, cognitive impairments, hyper-reflexia
Summary: Effects of inert gas narcosis
Effects are not pronounced
Perceptible decrement that is major and noticeable
Severe effects which are very dangerous
Symptoms resemble the effects of psychedelic drugs and considerable unconsciousness
Cause of Inert Gas Narcosis
Indeed, the exact causes of inert gas narcosis or effect are not clear. Nevertheless, the causes are closely related to the apparent increase in the solubility of particular gases in the body tissues and membranes at increased pressures. Research suggests that the narcotic potential of a particular gas is widely related to its solubility in lipids, which are the fatty materials that form the core components of the cells, particularly the nerve cells. Narcosis takes place at the junctions of the synapses. The inert gases, especially nitrogen under pressure, inhibit the normal electrical transfer between the different nerve cells thus resulting into the expansion of the synaptic membrane. Subsequently, the electrical impulses or information that is transferred from one nerve cell to the other occurs at a slower rate and this interferes with certain sections of the brain that are responsible for functions such as coordination and alertness.
Nitrogen is undoubtedly the main component of air and it widely used in deep sea diving as compared to Helium and Hydrogen. It leads to Nitrogen narcosis in deep-sea divers, therefore is use is restricted to shallow water diving. When the total gas pressure increases with the dive depth, there is a subsequent increase in nitrogen's partial pressure and more nitrogen is dissolved into the body tissue and blood. The increase in nitrogen concentration in the blood leads to the impairment in the nerve impulses. Nitrogen narcosis is very evident when the divers go beyond 30 metres or 100 feet below sea level but can occur at shallower depths. It actually affects all divers but some don't notice it effects.
Signs and Symptoms of Nitrogen Narcosis
Mental stimulation associated with great confidence
Loss of balance
Fixation of ideas
Impairment of complex reasoning
Lowered reaction time
Psychomotor and intellectual decrements
Preventing Nitrogen Narcosis
Nitrogen narcosis can be prevented in various ways. Essentially, nitrogen narcosis can be prevented by using diving gases that exclude or limit nitrogen such as "trimix" in commercial deep diving. Helium can be used to substitute nitrogen and dilute oxygen in commercial diving. Helium is odourless, tasteless, colourless and chemically inert. Nevertheless, helium is very expensive than nitrogen and has the potential of daring excessive body heat from the divers. Even though helium may also have certain effects (helium narcosis) under pressure, the effects are less severe as compared nitrogen narcosis.
Additionally, nitrogen narcosis can also be prevented by diving at lower depths and this can be achieved by following the outlined diving regulations practices, which include low work effort, proper maintenance of diving equipment, maintenance of visual cues, proper buoyancy and focused thinking. Narcosis gets worse with the increase in diving depth and a diver who maintains shallow diving can avert the adverse effects of narcosis. In most instances, special training should be recommended for air diving of up to 30 metres below sea level. The training should encompass the discussions and education on narcosis and its effects, treatment and prevention.
Research suggests that most divers can ascertain the depths that are likely to trigger narcosis on a given day. Moreover, the subtle symptoms of narcosis are usually very predictable and expected. Some divers may have trouble with their eyesight; others may have feelings of claustrophobia while other may have feelings of euphoria. Informed specialists training and coaching has the potential of enabling the divers to recognise personal commencement of the signs and symptoms and these may be used to signals for ascending to shallow depths before the symptoms become adverse.
Moreover, the divers should always ascertain their mental states before they embark of deep diving, this can be done using the "thumbs test". The "thumbs test" occurs when two or more divers show their fingers to each other to determine consciousness. One diver shoes the other two or more fingers and the other is compelled to respond by showing one less or more depending on their initial agreement. When any of the divers fails to provide the expected response, narcosis should be suspected. Some drugs are very sedative and they have similar effects to narcosis, therefore, their consumption must be avoided within 24 hours before diving. A drug like alcohol leads to dehydration, which increases the risk for decompression sickness, hangover, and a relatively compromised physical capacity and these factors can increase the likelihood of narcosis. A drug like marijuana has a very long half-life and this makes its abstinence time to be longer than that for alcohol.
Helium is an inert gas that is less narcotic than nitrogen at an equivalent pressure levels therefore, it is more suitable for deeper commercial dives than nitrogen. Helium is also used in commercial diving, it is not easily absorbed into the bloodstream as compared to oxygen or nitrogen, and divers who use it are able to go deeper for relatively longer periods. Essentially, helium is much lighter than nitrogen hence it bleeds out of the body at a faster rate decreasing the decompression time. Of the three gases, Helium gas has the lowest narcotic potency. Helium is mixed with oxygen to create heliox and the amount of heliox used in diving varies according to the depth that a particular diver is expected to go. When diving, it is always recommended that commercial divers increase the helium percentages as they dive deeper into the waters and decrease the percentage of helium when the depth of the dive is relatively shorter.
Ideally, it is not safe to breathe heliox at shorter depths because the divers may not have adequate oxygen to perform their normal physiological functions. Further, helium has a very high thermal conductivity, which makes the divers that use its mixtures to lose so much heat during deep diving. Heliox transfers heat approximately seven times more than air or Nitrox, therefore, the commercial divers that use the heliox mixtures rapidly become very cold by loss of body heat through the process of respiration. Therefore, the thermal protection garments for heliox mixtures should employ active heating to avert heat loss. This can be done by using s flow of hot water through a shroud over the pinning through which the driver's breathing air flows.
The narcotic effects of helium occur at 400 m below sea level. The symptoms that occur are slightly different form the known narcotic symptoms and are widely referred to as High Pressure Nervous Syndrome (NPNS). NPNS is a very serious problem in deep commercial diving especially where depths of over 130 metres are involved. The initial sign of NPNS is usually uncontrollable tremor coupled with muscle twitching and complexity in controlling movements. In the event that the diver continues descent, other signs such as confusion, disorientation, drowsiness, and unconsciousness may follow. Additionally, respiration may also be hampered by the neurologically induced muscle activity. The characteristic tremor majorly affects the arms and hands and resembles the shivering that is occasioned by cold weather, which is also produced by helium. The major disadvantage of helium in deep sea diving is that it is very expensive and this limits its use in deep sea diving.
Signs and Symptoms of Helium Narcosis
The most evident signs of helium narcosis include:
Course tremors especially of the hands which may improve after one or two hours
Feelings of weakness
Nausea and dizziness
The symptoms of helium narcosis are often very different from the symptoms of nitrogen narcosis, both in their nature and their behaviour with time. In effect, it is perceived that the symptoms of helium narcosis are occasioned by a multiplicity of factors. Nevertheless, it is also very likely that the narcotic effects of helium are responsible for some of the symptoms (Bennett et al., 2003).
Prevention of Helium Narcosis
As aforementioned, nitrogen narcosis commences at diving depths that are beyond 400 metres above below sea level. The symptoms that occur during helium narcosis are slightly different form the known narcotic symptoms and are widely referred to as High Pressure Nervous Syndrome (NPNS). Indeed, by slowing the descent rate by approximately 8 fsw/hr or even less the HPNS symptoms can be minimised greatly. Research suggests that there is often some recovery at depth, therefore, by allowing prolonged compression instances, the divers can have adequate time to adapt to the HPNS symptoms. The appearance of some of the clinical signs and symptoms during decompression can widely be avoided when the rates of ascent are controlled as stipulated by the various diving guidelines and tables such as the ones used by the Royal Navy or the U.S. Navy (Bennett et al., 2003). Moreover, most commercial divers also use helium-nitrogen-oxygen (Tri-mix) mixtures. The small percentage of nitrogen is used to reduce HPNS. The addition of nitrogen in the Tri-mix also enhances speech comprehension and may slightly reduce the heat loss that is associated with the use of helium in deep sea diving.
Hydrogen is also used in commercial deep sea diving because of its lower molecular weight, which makes it easier to breath at lower depths than helium. However, hydrogen has several narcotic effects that are even worse than Nitrogen and so it cannot be used as the primary inert gas in deep sea diving. Hydrogen narcosis refers to the psychotropic state occasioned by breathing hydrogen at very high pressures. The narcotic effects of nitrogen emerge at 1.6 MPa~2MPa (1), that is, Hydrogen narcosis commences or starts at 300 m or 1000 feet below sea level. Some of the widespread symptoms of hydrogen narcosis include:
Signs and symptoms of Hydrogen Narcosis
Indeed, these symptoms are similar to the ones experienced after the consumption of hallucinogenic drugs.
Prevention of Hydrogen Narcosis
Nitrogen narcosis commences or is noticed at depths of 300 metres below sea level and above. It is best prevented through early recognition and return to manageable water depths. Just like in nitrogen narcosis, some drugs such as alcohol and marijuana should be avoided within 24 hours of diving. Additionally, Hydrogen narcosis can also be prevented by diving at lower depths and this can be achieved by following the outlined diving regulations practices, which include low work effort, proper maintenance of diving equipment, maintenance of visual cues, proper buoyancy and focused thinking. Narcosis gets worse with the increase in diving depth and a diver who maintains shallow diving can avert the adverse effects of narcosis. In most instances, special training should be recommended for air diving of up to 300 metres below sea level.
General Prevention and Treatment of Narcosis
As aforementioned, narcosis is widely caused by deep sea diving. Therefore, narcosis is best prevented by avoiding compressed air diving to depths that are known to cause narcosis. Ideally, the recommended depth limits are 30-40 meters below sea level and this is dependent on the diver's tolerance to narcosis, experience and the task to be undertaken. Safe and secure diving that goes beyond 30 meters requires an in-depth awareness of the risks associated with narcosis and its potential effects of overall human functions and judgments. Some professional divers have been able to perform specific tasks at depths of up to 60 meters with impeccable skill. Dives greater than 50 meters should be considered as excessive and risky for commercial divers.
Ideally, a diver affected or incapacitated by narcosis should be protected from inappropriate behaviours or any form of physical injury, and brought to shallow depths with a controlled rise, with special emphasis on the decompression necessities and requirements. Therefore, the divers recover from this condition by ascending to shallow depths where the narcotic effects of the gases are reduced.
The signs and symptoms of narcosis usually clear very fast as the gas pressure is diminished. Further, the symptoms that are still visible or inherent on surfacing such as near drowning, salt-water aspiration and decompression sickness are necessitated by complications resulting from experiencing narcosis at depth, that is, they are not necessarily the symptoms of narcosis (Bennett et al., 2003).
General Management of Inert Gas Narcosis
Management of inert gas narcosis can be very difficult, however, frequent deep diving into the range of nitrogen narcosis can lead to some adaptation but this can last into days or weeks. A considerable number of deep divers learn to cope with the effects of narcosis by minimizing and simplifying their tasks during deep diving. This can be done by ensuring that the they plan and concentrate on their core activities while at depth. When the diver go beyond 30 metres oxygen-nitrogen or oxygen-helium mixtures are recommended.
There is no doubt that cautious and detailed planning is very essential for all deep diving. All divers should be very aware of the effects of inert gas narcosis on nay dive that is below 25 metres in unfavourable circumstances (strong current, poor visibility, cold water) as is may not be similar to clear water diving. Divers should avoid deep sea diving whenever their visible references are unclear. Further, they should be very careful to check the uncontrolled descent and limit the dive. The depth, air pressure and bottom time should be monitored frequently and the recommended or pre-planned limits should not be exceeded. When diving in pairs, any unusual behaviour on a colleague's part such as confusion, over-emphatic signals, should be taken seriously and if they are evident, the dive should be aborted.
In conclusion, Inert gas narcosis is a condition that affects the mental and physical states of individuals breathing air or mixtures containing some of the inert gases such as helium, nitrogen or hydrogen at pressures that are greater than four atmospheres.
Research suggests that the narcosis is widely occasioned by the retention of the gases in the human blood or tissue. Some of the gases that are used in diving that are responsible for narcosis include Helium, Nitrogen and Hydrogen. Helium is responsible for narcosis at depths of 400 metres and above, nitrogen at depths of 30 metres and above and hydrogen at depths of 300 metres and above.