**1. Introduction**

Inert gases are shown to have an effect in the body without entering metabolic and chemical activities [1]. The inert gas, which is nitrogen, encountered with problems in sports equipped divers. For this reason, what is known as inert gas narcosis in diving medicine can be called direct nitrogen narcosis in this chapter [2].

Nitrogen narcosis, depth poisoning, depth drunkenness, nitrogen narcosis is also known by other names [1]. The nitrogen that the two nitrogen molecules bind with three bonds between

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

them constitutes 79% of the air we breathe [3]. The increase of the nitrogen pressure negatively affects the central nervous system (CNS). It is usually seen at depths of more than 30 m [4]. Nitrogen narcosis is characterized by decreased intellectual function and decreased neuromuscular transmission performance, a tendency to laugh, decreased attention and decisionmaking, emotional state, and impaired behavior. Nitrogen narcosis does not cause permanent damage to the body, but mental and motor deterioration can lead to serious problems in the underwater [2]. These effects increase as the partial pressure of nitrogen increases, but it is not related to the time remaining at the same depth [5]. These changes have been seen for centuries as they are known when diving with compressed air due to nitrogen pressure. Other inert gases with similar effects have been described (neon, argon, krypton, xenon, and hydrogen) [1].

enthusiasm (euphoria) developed at the 30-m compressed air dive; accompany slowing of the mental capacity and deterioration of the nerve-muscle communication. Attention was paid to the fact that this effect was further enhanced by the depth of the dive. At diving, drowsiness occurs at 90 m and loss of consciousness occurs at 90–140 m. Behnke and Yarbrough reported that this effect could be reduced by replacing nitrogen to helium in the dive inhalation gas [1]. According to the Deep Dive Committee Report in 1933, this was also related to the accumulation of carbon dioxide during the dive. In 1941, Case and Haldane showed that, when carbon dioxide was mixed in the diving air, the mental symptoms became more intense. However, In some studies clearly denied the carbon dioxide theory. They showed evidence of narcotic symptoms despite normal levels of carbon dioxide in the alveolar air. In subsequent years of studies has been found that direct anesthesia is responsible for the nitrogen between the air

Toxic Effects of Hyperbaric Conditions http://dx.doi.org/10.5772/intechopen.78392 111

It is thought that the mechanism of nitrogen narcosis is the same as general anesthesia with volatile gases. All inert gases that produce anesthetic effects behave in the same way. These gases are composed of simple molecules with no structural properties and do not show

Many researchers have attempted to understand the physical behavior of these gases and have found a close relationship with the oil dissolution feature. According to the Meyer-Overton hypothesis, there is a parallel between the dissolution of anesthetics in oil and potency of the narcotic effect. It stated that when the gases pass through cell oils at a certain molar concentration, they will show an effect of narcosis. In this case, the inert gas molecule affects the cell membrane function in the brain. However, there are some discrepancies in terms of the physical properties of the inert gases and their narcotics abilities (**Table 1**). For example, argon is two times more narcotic than nitrogen. However, their fat/water solubility ratios are similar. However, despite all these incompatibilities, narcotic behavior is parallel to physical

According to Henry's Law, as soon as the partial pressure of nitrogen increases, it begins to dissolve more in the body and in the plasma. Nitrogen cannot be used by the body like oxygen. When we breathe compressed air during diving, many molecules enter our bodies and quickly dissolve in our bodies due to the height of the environmental pressure. When we dive 15 m sea water, the nitrogen partial pressure will double up. With the increase in depth, the narcosis signs will begin to appear. As is known, anesthetic symptoms occur when diving

The dissolution hypothesis in oil has been tried to be understood by the concept of critical volume. Here, in order to develop the effect of narcosis, the inert gas must affect on the fat part of cell membrane to swell. In human studies, it has been confirmed that gas has a positive

is 15 m or more, and we briefly explain it with the Martini Act (**Figure 1**) [4].

correlation with oil solubility by developing slightly to moderate narcosis.

and dive with helium/oxygen [2].

chemical changes in the body [3].

characteristics in general [5].

**3. Etiology**

In diving with compressed air, nitrogen narcosis is the most important factor limiting depth. When it is necessary to work deeper than 40–50 m, it is necessary to get help from gas with less narcotic effect such as helium. Nitrogen narcosis is responsible for most of the dive accidents and dive-related deaths.

The cause of acute toxicity of hyperbaric oxygen therapy is related to oxygen partial pressure [6]. Although oxygen is a necessary gas to survive, oxygen can show toxic effects at high partial pressures and long-term exposures. Oxygen poisoning can be seen in long-term oxygen therapy in intensive care, in closed or semi-closed circuit diving, in saturation dives, on decompressions on the surface, in recompression and hyperbaric oxygen therapy [7].

Oxygen intoxication is caused by reactions between free oxygen radicals and cell components [8]. Gamma amino butyric acid (GABA) has frequently been studied in studies conducted in this regard [9]. Excess oxygen causes the generation of uncontrolled stimuli in the central nervous system by reducing GABA outflows [8]. It is thought that seizures developing in 3 ATA and above hyperbaric oxygen therapy are related to this [10].
