Diving medicine

2020 ◽  
pp. 1664-1671
Author(s):  
David M. Denison ◽  
Mark A. Glover
Keyword(s):  
Central Nervous System ◽  
Partial Pressure ◽  
Ambient Pressure ◽  
Rapid Change ◽  
Inert Gases ◽  
Gas Mixture ◽  
Generalized Seizures ◽  
Partial Pressures ◽  
Diving Medicine ◽  
The Central Nervous System

Diving remains the principal means of exploring and exploiting shallower underwater zones. Immersion and rapid change in pressure with depth cause most problems unique to diving. Gas density, partial pressures, and solubility vary proportionately with ambient pressure. At elevated partial pressure, nitrogen becomes narcotic, as can other inert gases, and contaminants barely detectable at the surface can become toxic. Hyperoxia irritates the lungs and the central nervous system, sometimes causing generalized seizures. A safe gas mixture at depth can become hypoxic as the partial pressure of oxygen decreases during the return to surface. Ventilation is compromised at depth and failure of CO2 elimination increasingly limits activity. Some divers are not distressed by elevated CO2, but this does not protect them from its toxic effects.

Diving medicine

2010 ◽  
pp. 1416-1422
Author(s):  
D.M. Denison ◽  
M.A. Glover
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Partial Pressure ◽  
Ambient Pressure ◽  
Inert Gases ◽  
Gas Mixture ◽  
Generalized Seizures ◽  
Partial Pressures ◽  
Diving Medicine ◽  
The Central Nervous System

Diving remains the principal means of exploring and exploiting shallower underwater zones. Immersion and rapid increase in pressure with depth cause most problems unique to diving. Gas density, partial pressures, and solubility vary proportionately with ambient pressure. At elevated partial pressure, nitrogen becomes narcotic, as can other inert gases, and contaminants barely detectable at the surface can become toxic as their partial pressures rise with depth. Hyperoxia irritates the lungs and the central nervous system, and sometimes causing generalized seizures. A safe gas mixture at depth can become hypoxic as the partial pressure of oxygen decreases during the return to surface....

scholarly journals Neuronal sensitivity to hyperoxia, hypercapnia, and inert gases at hyperbaric pressures

2003 ◽  
Vol 95 (3) ◽  
pp. 883-909 ◽  
Author(s):  
Jay B. Dean ◽  
Daniel K. Mulkey ◽  
Alfredo J. Garcia ◽  
Robert W. Putnam ◽  
Richard A. Henderson
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Ambient Pressure ◽  
Inert Gases ◽  
Neuronal Function ◽  
Cellular Mechanisms ◽  
Electrophysiological Studies ◽  
The Central Nervous System ◽  
Electrophysiological Methods

As ambient pressure increases, hydrostatic compression of the central nervous system, combined with increasing levels of inspired Po2, Pco2, and N2partial pressure, has deleterious effects on neuronal function, resulting in O2toxicity, CO2toxicity, N2narcosis, and high-pressure nervous syndrome. The cellular mechanisms responsible for each disorder have been difficult to study by using classic in vitro electrophysiological methods, due to the physical barrier imposed by the sealed pressure chamber and mechanical disturbances during tissue compression. Improved chamber designs and methods have made such experiments feasible in mammalian neurons, especially at ambient pressures <5 atmospheres absolute (ATA). Here we summarize these methods, the physiologically relevant test pressures, potential research applications, and results of previous research, focusing on the significance of electrophysiological studies at <5 ATA. Intracellular recordings and tissue Po2measurements in slices of rat brain demonstrate how to differentiate the neuronal effects of increased gas pressures from pressure per se. Examples also highlight the use of hyperoxia (≤3 ATA O2) as a model for studying the cellular mechanisms of oxidative stress in the mammalian central nervous system.

SOME EFFECTS OF DHSOPROPYL FLUOROPHOSPHATE (DFP) AND FLUOROACETATE ON THE CENTRAL NERVOUS SYSTEM

1949 ◽  
Vol 27e (2) ◽  
pp. 146-157 ◽  
Author(s):  
Andrew Kelen ◽  
Donald McEachern
Keyword(s):  
Central Nervous System ◽  
Intravenous Injection ◽  
Plasma Cholinesterase ◽  
The Other ◽  
Diisopropyl Fluorophosphate ◽  
Intravenous Injections ◽  
Hind Limbs ◽  
Generalized Seizures ◽  
The Central Nervous System ◽  
Systemic Symptoms

Attempts were made to produce convulsions in cats by intracarotid and intracisternal injections of diisopropyl fluorophosphate (DFP). No convulsions were obtained in either instance. Systemic symptoms appeared, however, and plasma cholinesterase was sharply reduced. Intracarotid DFP produced prolonged ipsilateral myosis and salivation. E.E.G. changes on the side of the injection were found in one of two trials. Intracisternal DFP caused prolongation (threefold) of the pentothal anesthesia. The animals, upon awakening, showed a temporary loss of sensation in the forelimbs and cornea with weakness of the hind limbs and a waddling gait. Intracisternal fluoroacetate produced curious generalized seizures. These were classified as scissors spasms, scratching seizures, and myoclonic jerks. They appeared after about three-quarters of an hour, in contrast to the latent period of two to three hours after intravenous injection. Seizures persisted for hours unless stopped with nembutal. Cerebrospinal fluid (CSF) was tested for acetylcholine (ACh), the minimum amount detectable during our experiments being 0.4 to 3.0 μgm. %. After intravenous injections of 1.5 mgm. per kgm. of DFP preceding convulsions produced by thujone, small amounts of ACh appeared in three out of four experiments. Intravenous injection of 5.0 mgm. per kgm. of DFP resulted in 3.0 μgm. % of ACh in the CSF. No ACh was found after the other procedures described.

Cortical CO2 and O2 at high pressures of argon, nitrogen, helium, and oxygen

1965 ◽  
Vol 20 (6) ◽  
pp. 1249-1252 ◽  
Author(s):  
Peter B. Bennett
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
High Pressures ◽  
Inert Gases ◽  
Inert Gas ◽  
Low Oxygen ◽  
Nitrogen Narcosis ◽  
Partial Pressures ◽  
Argon Mixture

In 37 chloralosed cats (45–50 mg/kg) exposed to increased pressures of argon, nitrogen, or helium between 8.67 and 10.8 atm abs in the presence of either 0.2 or 2.34 atm abs oxygen or oxygen alone, the cortical carbon dioxide was measured with a modified Severinghaus electrode and the cortical oxygen polarographically. In mixtures with an oxygen partial pressure of 2.34 atm abs, the cortical oxygen increased above controls. The greater the density of the mixture then, the less was the increase. The cortical carbon dioxide also increased, but conversely, the greater the density of the mixture the greater the increase in carbon dioxide. In mixtures of low oxygen partial pressures, the cortical oxygen was below control values whereas the carbon dioxide showed little change except for a slight increase with the heavier argon mixture. Inert gas narcosis, as indicated by depression of auditory induced cortical spikes, did not correlate with the changes in cortical carbon dioxide but with the inert gas itself. Increasing the oxygen partial pressure and the density of the mixture respired caused retention of brain carbon dioxide, which synergistically potentiated the narcosis. nitrogen narcosis; inert gases; depth intoxication; tissue carbon dioxide; tissue oxygen; brain Submitted on August 10, 1964

scholarly journals Partial Pressures in Thermodynamics of Classical Fluid Mixtures

2012 ◽  
Vol 5 (1) ◽  
pp. 29-36 ◽  
Author(s):  
Vít Samohýl ◽  
Ivan Samohýl ◽  
Petr Voňka
Keyword(s):  
Carbon Dioxide ◽  
Partial Pressure ◽  
Liquid Mixture ◽  
Ideal Gas ◽  
Lithium Hydroxide ◽  
Gas Mixture ◽  
Real Gas ◽  
Fluid Mixtures ◽  
Classical Fluid ◽  
Partial Pressures

Partial Pressures in Thermodynamics of Classical Fluid Mixtures In the rational thermodynamics of most usual nonequilibrium "classical" fluid mixtures it has been proposed the "thermodynamic" partial pressure which generalize traditional definitions and merge together in an ideal gas mixture. In this paper, these thermodynamic partial pressures are calculated for a (real) gas mixture of methane-ethane-carbon dioxide and a liquid mixture of lithium hydroxide in water. The results are compared with those obtained using the classical formulations of partial pressures calculated in these mixtures as well.

Effects of Hyperoxia on Lung Utrastructure

1970 ◽  
Vol 28 ◽  
pp. 26-27
Author(s):  
Gladys Harrison
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Light Microscopy ◽  
Oxygen Effects ◽  
Age Dependent ◽  
The Central Nervous System ◽  
The Subject ◽  
Space Age ◽  
Alveolar Septa ◽  
Extensive Damage

With the advent of the space age and the need to determine the requirements for a space cabin atmosphere, oxygen effects came into increased importance, even though these effects have been the subject of continuous research for many years. In fact, Priestly initiated oxygen research when in 1775 he published his results of isolating oxygen and described the effects of breathing it on himself and two mice, the only creatures to have had the “privilege” of breathing this “pure air”.Early studies had demonstrated the central nervous system effects at pressures above one atmosphere. Light microscopy revealed extensive damage to the lungs at one atmosphere. These changes which included perivascular and peribronchial edema, focal hemorrhage, rupture of the alveolar septa, and widespread edema, resulted in death of the animal in less than one week. The severity of the symptoms differed between species and was age dependent, with young animals being more resistant.

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