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High-pressure nervous syndrome

High-pressure nervous syndrome (HPNS – also known as high-pressure neurological syndrome) is a neurological and physiological diving disorder that results when a diver descends below about Script error: No such module "convert". using a breathing gas containing helium. The effects experienced, and the severity of those effects, depend on the rate of descent, the depth and percentage of helium.[1]

"Helium tremors" were first widely described in 1965 by Royal Navy physiologist Peter B. Bennett, who also founded the Divers Alert Network.[1][2] Russian scientist G. L. Zal'tsman also reported on helium tremors in his experiments from 1961. However these reports were not available in the West until 1967.[3]

The term high pressure nervous syndrome was first used by Brauer in 1968 to describe the combined symptoms of tremor, electroencephalography (EEG) changes, and somnolence that appeared during a Script error: No such module "convert". chamber dive in Marseille.[4]

Symptoms

Symptoms of HPNS include tremors, myoclonic jerking, somnolence, EEG changes,[5] visual disturbance, nausea, dizziness, and decreased mental performance.[1][2]

Causes

HPNS has two components, one resulting from the speed of compression and the other from the absolute pressure. The compression effects may occur when descending below Script error: No such module "convert". at rates greater than a few metres per minute, but reduce within a few hours once the pressure has stabilised. The effects from depth become significant at depths exceeding Script error: No such module "convert". and remain regardless of the time spent at that depth.[1]

The susceptibility of divers and animals to HPNS varies over a wide range depending on the individual, but has little variation between different dives by the same diver.[1]

Prevention

It is likely that HPNS cannot be entirely prevented but there are effective methods to delay or change the development of the symptoms.[1][6]

Utilizing slow rates of compression or adding stops to the compression have been found to prevent large initial decrements in performance.[1][7]

Including other gases in the helium–oxygen mixture, such as nitrogen (creating trimix) or hydrogen (producing hydreliox) suppresses the neurological effects.[8][9][10]

Alcohol, anesthetics and anticonvulsant drugs have had varying results in suppressing HPNS with animals.[1] None are currently in use for humans.[citation needed]

See also

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References

  1. ^ a b c d e f g h Bennett, Peter B; Rostain, Jean Claude (2003). "The High Pressure Nervous Syndrome". In Brubakk, Alf O; Neuman, Tom S. Bennett and Elliott's physiology and medicine of diving, 5th Rev ed. United States: Saunders. pp. 323–57. ISBN 0-7020-2571-2. 
  2. ^ a b Bennett, P. B. (1965). "Psychometric impairment in men breathing oxygen-helium at increased pressures". Royal Navy Personnel Research Committee, Underwater Physiology Subcommittee Report No. 251 (London). 
  3. ^ Zal'tsman, G. L. (1967). "Psychological principles of a sojourn of a human in conditions of raised pressure of the gaseous medium (in Russian, 1961)". English translation, Foreign Technology Division. AD655 360 (Wright Patterson Air Force Base, Ohio). 
  4. ^ Brauer, R. W. (1968). "Seeking man's depth level". Ocean Industry (London) 3: 28–33. 
  5. ^ Brauer, R. W.; S. Dimov; X. Fructus; P. Fructus; A. Gosset; R. Naquet. (1968). "Syndrome neurologique et electrographique des hautes pressions". Rev Neurol (Paris) 121 (3): 264–5. PMID 5378824. 
  6. ^ Hunger Jr, W. L.; P. B. Bennett. (1974). "The causes, mechanisms and prevention of the high pressure nervous syndrome". Undersea Biomed. Res. 1 (1): 1–28. ISSN 0093-5387. OCLC 2068005. PMID 4619860. Retrieved 2008-04-07. 
  7. ^ Bennett, P. B.; R. Coggin; M. McLeod. (1982). "Effect of compression rate on use of trimix to ameliorate HPNS in man to 686 m (2250 ft)". Undersea Biomed. Res. 9 (4): 335–51. ISSN 0093-5387. OCLC 2068005. PMID 7168098. Retrieved 2008-04-07. 
  8. ^ Vigreux, J. (1970). "Contribution to the study of the neurological and mental reactions of the organism of the higher mammal to gaseous mixtures under pressure". MD Thesis (Toulouse University). 
  9. ^ Fife, W. P. (1979). "The use of Non-Explosive mixtures of hydrogen and oxygen for diving". Texas A&M University Sea Grant. TAMU-SG-79-201. 
  10. ^ Rostain, J. C.; Gardette-Chauffour, M. C.; Lemaire, C.; Naquet, R. (1988). "Effects of a H2-He-O2 mixture on the HPNS up to 450 msw". Undersea Biomedical Research 15 (4): 257–70. ISSN 0093-5387. OCLC 2068005. PMID 3212843. Retrieved 2008-04-07. 

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