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Topic: High pressure nervous syndrome

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Helium

Tony Trimmer

Papilla

Lansing (village), New York

USC Interactive Media Division

	Glossary
		Also, a unit of pressure; "one atmosphere" is pressure of the atmosphere at sea level, i.e., 760 mm Hg.
		The anatomy of this tube is such that it tends to close naturally when ambient pressure is higher than middle ear pressure (as on descent in a dive), and tends to open naturally when ambient pressure is lower than middle ear pressure (on ascent).
		Air pressure in the middle ear space can only be equalized through the eustachian tube, which connects the middle ear to the back of the nose.
	www.lakesidepress.com /pulmonary/books/scuba/sectionq.htm (2781 words)

	Postgraduate Medicine: Patient Notes: High blood pressure
		When high blood pressure is caused by another disorder (for example, heart or kidney disease, sleep apnea, thyroid disease, or obesity) or use of certain drugs (for example, oral contraceptives), it is called secondary hypertension.
		When high blood pressure is present in combination with abdominal obesity and high levels of cholesterol and blood sugar, the risk of heart disease is higher than when any of these conditions occurs alone.
		High blood pressure is called a silent disease, because in most cases there are no symptoms.
	www.postgradmed.com /issues/2005/07_05/pn_pressure.htm (712 words)

	High blood pressure (hypertension) - causes, treatments and medications
		Accordingly, ACE inhibitors usually are the first line drugs of choice to treat high blood pressure in cases that also involve congestive heart failure, chronic kidney failure in both diabetics and non-diabetics, and heart attack (myocardial infarction) that weakens the heart muscle (systolic dysfunction).
		The sympathetic nervous system is a part of the nervous system that helps to regulate certain involuntary (autonomic) functions in the body such as the function of the heart and blood vessels.
		The nerves of the sympathetic nervous system extend throughout the body and exert their effects by releasing chemicals that travel to nearby cells in the body, for example, muscle cells.
	www.medicinenet.com /high_blood_pressure/page9.htm (2266 words)

	APStracts 10:0267A, 2003. (Site not responding. Last check: 2007-10-13)
		Neuronal sensitivity to pressure, barosensitivity, is illustrated by high-pressure nervous syndrome, which manifests as increased central nervous system excitability when heliox or trimix is breathed at >15 atmospheres absolute (ATA).
		The effect of hyperbaric helium, which mimics increased hydrostatic pressure, was determined on putative CO2/H+-chemoreceptor neurons in the solitary complex in rat brain stem slices by intracellular recording.
		Neuronal barosensitivity to =4 ATA may represent a physiological adaptive response to increased pressure or an early pathophysiological response that is the early manifestation of high-pressure nervous syndrome.
	www.uth.tmc.edu /apstracts/2003/jap/June/267a.html (253 words)

	What Causes High Blood Pressure?
		High blood pressure with an unknown cause is called essential, or primary, hypertension.
		While most people with high blood pressure cannot attribute it to a specific cause, the other 5 to 10 percent of people with high blood pressure have an underlying condition that causes it.
		Isolated systolic hypertension refers to a situation in which only the systolic blood pressure (the first number of the blood pressure measurement) is high, 140 mm Hg or greater, and the diastolic blood pressure (the second number) is normal or at the high end of normal (below 90 mm Hg).
	www.ehealthmd.com /library/highbp/HBP_causes.html (1148 words)

	Narcosis - The Deco Stop
		High mental capacity is a requirement when subjected to harsh environments such as being deep under the water.
		Thus, at 10 msw the absolute pressure is 0.2 Mpa, the sum of both 0.1MPa of atmospheric pressure and 0.1MPa of hydrostatic pressure and at a depth of 40 msw, the absolute pressure is 0.5 MPa.
		For a diver’s lungs to be able to counter the increased external pressure at depth underwater, the inspired air is delivered at a pressure slightly greater than the ambient pressure, resulting in partial pressures of the gases in the breathing mixture being greater than that of sea level.
	thedecostop.com /forums/showthread.php?t=7599 (3834 words)

	speak mix man
		Pg = P x Fg where Pg is the partial pressure of a gas, g, and is equal to the total pressure, P, of the gas mixture times the proportion or fraction of the gas in the mixture, Fg.
		Calculating the partial pressure of a gas, for example PO2 or PN2, given the working depth in pressure and the fraction in the mix.
		The severity of oxygen's toxic effect depends on the dose measured in partial pressure, and the duration of the exposure.
	www.cisatlantic.com /trimix/AQUAcorps/mix/techspeak.htm (1265 words)

	Diving Physics and Fizzyology
		The partial pressure of a particular gas constituent in a gas mixture is a representation of the portion of the total pressure of the gas mixture exerted by the particular constituent.
		At 99 feet (30 meters), the ambient pressure is four times greater than it is at the surface, and the partial pressures of each of the gases is also four times greater (although the percentages of each gas are the same in both cases).
		Because the partial pressures of the gases in the lungs are now greater than the dissolved partial pressures of these gases in the blood in tissues, gas molecules begin to move from the lungs into the blood and tissues (represented by the blue and red arrows in the middle figure, 2).
	www.iantd.com /rebreather/phys.html (5415 words)

	Modulation of Rat Corticohippocampal Synaptic Activity by High Pressure and Extracellular Calcium: Single and Frequency ...
		high pressure of helium (Talpalar and Grossman 1994
		Effects of high pressure on the channel gated by the quisqualate-sensitive glutamate receptor of locust muscle and its blockade by ketamine; a single-channel analysis.
		Glycine activation of human homomeric alpha 1 glycine receptors is sensitive to pressure in the range of the high pressure nervous syndrome.
	jn.physiology.org /cgi/content/full/90/4/2106 (4761 words)

	High Pressure Nervous Syndrome
		There are also other major disadvantages to diving with helium mixes; it is more difficult to decompress, i.e., deeper and longer stops are required as compared to air; and there is a greater risk of a serious case of decompression sickness if stops are not done per plan.
		HPNS is characterized in humans by dizziness, nausea, vomiting, postural and intention tremors, fatigue and somnolence, myoclonic jerking, stomach cramps, decrements in intellectual and psychomotor performance, poor sleep with nightmares, and increased slow wave and decreased fast wave activity of the brain as measured by an electroencephalogram (Bennett et al.
		The high pressure nervous syndrome in man. In: The Physiology and Medicine of Diving and Compressed Air Work.
	www.scuba-doc.com /HPNS.html (666 words)

	Wired 3.11: Under Pressure
		Pressure this great can implode even the best diving equipment as easily as you could crush a styrofoam cup.
		Its effects on the body can be just as dramatic, making the range of physiological barriers read like an inventory of hyperbaric nightmares: decompression illness (a k a the bends), oxygen toxicity, high-pressure nervous syndrome, deep-water flout, and nitrogen narcosis.
		Water pressure will keep those gases compressed in the form of small, harmless bubbles - that is, until the divers return to the surface.
	www.wired.com /wired/archive/3.11/divers.html (873 words)

	Enhanced Excitability Compensates for High-Pressure-Induced Depression of Cortical Inputs to the Hippocampus -- ...
		Pressure effects on the AAP are summarized in Fig.
		The effects of hydrostatic pressure on the spontaneous release of transmitter at the frog neuromuscular junction.
		High pressure enhanced NMDA activity in the striatum and the globus pallidus: relationships with myoclonia and locomotor and motor activity in rat.
	jn.physiology.org /cgi/content/full/92/6/3309 (5550 words)

	Nervous System Problems -- Topic Overview
		The nervous system is divided into the brain and spinal cord (central nervous system, or CNS) and the nerve cells that control voluntary and involuntary movements (peripheral nervous system, or PNS).
		The symptoms of a nervous system problem depend on which area of the nervous system is involved and what is causing the problem.
		Nervous system problems may occur slowly and cause a gradual loss of function (degenerative), or they may occur suddenly and cause life-threatening problems (acute).
	www.webmd.com /hw/brain_nervous_system/hw97809.asp (245 words)

	Freelance Traveller - The Lab Ship - Atmospheres - General Notes and Oxygen
		The pressure of a gas is equivalent to the force its component molecules impart to the walls of its container.
		Partial pressure: the overall pressure exerted by a gas mixture is the sum of the pressures exerted by the components of the mixture.
		(Saturated) Vapour pressure: the pressure exerted by the gaseous component of a substance in equilibrium with its liquid component at a given temperature.
	www.freelancetraveller.com /features/science/atmos/atmo1.html (1996 words)

	3.11: Under Pressure
		It was high-pressure nervous syndrome, a little-understood phenomenon brought on by severe, rapid compression.
		The extreme pressure inhibits the function of the brain, causing neural circuits to run wild.
		He was most likely experiencing flashes of narcosis as well as another episode of high-pressure nervous syndrome.
	www.wired.com /wired/archive/3.11/divers_pr.html (3559 words)

	Dysbarism - Wikipedia, the free encyclopedia
		Ambient pressure is the pressure in the water around the diver (or the air, with caisson workers etc).
		As a diver descends, the ambient pressure increases.
		High pressure nervous syndrome is rarely of importance to recreational divers.
	en.wikipedia.org /wiki/Dysbarism (1077 words)

	Loyola Univ. Health Sys. - Nervous System Disorders - Guillain-Barre Syndrome (Site not responding. Last check: 2007-10-13)
		Guillain-Barre syndrome is a neurological disorder in which the body's immune system attacks part of the peripheral nervous system.
		Guillain-Barre is called a syndrome rather than a disease because it is not clear that a specific disease-causing agent is involved.
		A syndrome is a medical condition characterized by a collection of symptoms (what the patient feels) and signs (what a doctor can observe or measure).
	www.luhs.org /HEALTH/TOPICS/nervous/guillain.htm (671 words)

	Commercial Diving - Dysbarisms and Other Selected Health Effects
		If the pressure ratio is too large, bubbles form and symptoms of DCS occur, ranging from mildly irritating to severe.
		Oxygen toxicity effects to the central nervous system are more common in the time-frame of a working day, while pulmonary effects are more of a concern during saturation diving.
		Such partial pressures only occur from the accumulation of exhaled carbon dioxide at increased pressure (either in the breathing system's dead space or due to a system malfunction).
	www.osha.gov /SLTC/commercialdiving/more.html (1479 words)

	Science
		The damage of oxygen to the lung and brain will vary with partial pressure above 1 atmosphere and time of exposure and is a concern when the molar fraction of oxygen is increased, as in NITROX diving.
		Acute symptoms of DCS can occur during a decrease in pressure, but they occur most commonly soon after the ascent has been completed.
		At 300 feet of water the pressure is 10 times that of sea level.
	aboutfacts.net /Science2.htm (792 words)

	High pressure nervous syndrome - Wikipedia, the free encyclopedia
		High pressure nervous syndrome (HPNS) is a dangerous diving disorder that can arise when a diver spends too much time breathing a high-pressure mixture of helium and oxygen (heliox) at depths in excess of 130 metres (430 feet).
		Its symptoms include dizziness, nausea, vomiting, tremors, myoclonic jerking, and decreased intellectual performance.
		Bennett was a consultant on the James Cameron underwater science fiction film The Abyss, in which a character experiences HPNS.
	en.wikipedia.org /wiki/High_pressure_nervous_syndrome (164 words)

	Coastal Systems Station Uses CAD and FEA to Design and Test Deep Sea Breathing Apparatus Valve
		For diving beyond traditional depths of self-contained underwater breathing apparatus, a mixture of inert gases including helium and oxygen is used to prevent potentially deadly conditions such as oxygen poisoning, high pressure nervous syndrome and nitrogen narcosis.
		These components need to withstand high pressures because the breathing system must contain a large amount of gas in a compact area to provide sufficient life support for the duration required.
		K-Monel material was chosen for the valve because it withstands pressure, is self-extinguishing to avoid the possibility of oxygen fires, resists the corrosive effects of seawater, and enables removal of the adjacent bottle without galling the threads.
	www.algor.com /news_pub/cust_app/coastal/coastal.asp (610 words)

	Seroquel Warnings & Precautions (Site not responding. Last check: 2007-10-13)
		Clinical manifestations of NMS are hyperpyrexia, muscle rigidity, altered mental status, and evidence of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis, and cardiac dysrhythmia).
		The diagnostic evaluation of patients with this syndrome is complicated.
		Although the prevalence of the syndrome appears to be highest among the elderly, especially elderly women, it is impossible to rely upon prevalence estimates to predict, at the inception of antipsychotic treatment, which patients are likely to develop the syndrome.
	www.healthcentral.com /high-blood-pressure/index-127-133.html (437 words)

	High Blood Pressure
		First, blood pressure is the pressure of the blood as it moves within your body's vascular system.
		Your blood pressure is determined by a complex interaction of many organs in your body such as your heart, the diameter of your blood vessels, kidney function and your autonomic nervous system.
		Usually there are no sensations associated with high blood pressure, though some people report being able to sense when their blood pressure is high.
	www.lifematters.com /hypertension.asp (867 words)

	Life at the Extremes: The Science of Survival (Frances Ashcroft)
		Life at the Extremes is an account of the challenges that humans face in extreme environments: at high altitudes, under high pressures, at low and high temperatures, under extreme energetic demands, and in space.
		Ashcroft's focus is on physiology (her own area of expertise), but she ranges across medicine, the history of science, sport, exploration, and comparative zoology, and throws in some biographical and autobiographical anecdotes as well.
		The major problem here is the bends (when too rapid decompression causes nitrogen bubbles to form in the blood) but other concerns include nitrogen and oxygen toxicity and high pressure nervous syndrome.
	dannyreviews.com /h/Life_Extremes.html (842 words)

	Fizziology
		The source of this pressure is actually a result of the weight of the air in Earth's atmosphere.
		As is illustrated in the diagram at right, the ambient pressure increases underwater at an almost linear rate with increasing depth.
		Another way to overcome the problem of breathing under pressure is to provide a pressurized breathing gas mixture to the diver.
	www.floridascubahound.com /fizziology.htm (5460 words)

	ABC of oxygen: Diving and oxygen -- Wilmshurst 317 (7164): 996 -- BMJ
		At sea level atmospheric pressure is 1 bar absolute (1 standard atmosphere =101 kPa=1.013 bars).
		and high in carbon dioxide and nitrogen) be liberated as bubbles.
		dive the gas in a bulla increases as ambient pressure is reduced.
	bmj.bmjjournals.com /cgi/content/full/317/7164/996 (2100 words)

	Neuronal sensitivity to hyperoxia, hypercapnia, and inert gases at hyperbaric pressures -- Dean et al. 95 (3): 883 -- ...
		At extreme hyperbaric pressures (>100 ATA), pressure becomes a tool that can be used to perturb biological systems (in vitro) by altering protein conformation, membrane fluidity, and configuration of the cytoskeleton.
		pressure is unclear and is one of the areas of hyperbaric electrophysiology
		This, the decrease in input resistance measured during exposure to hyperbaric pressure, is indicative of an increase in membrane conductance.
	jap.physiology.org /cgi/content/full/95/3/883 (6933 words)

	Guillain-Barre Syndrome - Nervous System Diseases Health Guide
		Although the onset of Guillain-Barre syndrome is sudden and unexpected, recovery is often times not.
		If Guillain-Barre is preceded by a viral infection, it is possible that the virus changes the nature of cells in the nervous system causing the immune system to interpret them as foreign cells.
		Treatment for the syndrome mainly consists of keeping the patient's body functioning during recovery of the nervous system.
	www.umm.edu /nervous/guillain.htm (847 words)

	Shy-Drager syndrome - MayoClinic.com
		Shy-Drager syndrome is a rare, progressive degenerative disorder of the nervous system.
		The main characteristic of Shy-Drager is a severe drop in blood pressure on standing up or standing motionless (orthostatic hypotension).
		Also, blood pressure may be very high when lying down, due to failure of blood pressure control mechanisms.
	www.mayoclinic.com /health/shy-drager-syndrome/AN00616 (261 words)

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