High pressure nervous syndrome

High pressure nervous syndrome

High pressure nervous syndrome (HPNS) is a neurological and physiological diving disorder that results when a diver spends too much time breathing a high-pressure mixture of helium and oxygen (heliox).cite book |title=Bennett and Elliott's physiology and medicine of diving, 5th Rev ed. |last=Brubakk |first=A. O. |coauthors=T. S. Neuman |year=2003 |publisher=Saunders Ltd. |location=United States |isbn=0702025712 |pages=800 ] HPNS is a limiting factor in future deep diving.

"Helium tremors" were first described in 1965 by Royal Navy physiologist Peter B. Bennett, who also founded the Divers Alert Network.cite journal |last=Bennett |first=P. B. |title=Psychometric impairment in men breathing oxygen-helium at increased pressures |journal=Royal Navy Personnel Research Committee, Underwater Physiology Subcommittee Report No. 251 |date=1965 |location=London ] Zal'tsman also reported on helium tremors in his experiments from 1961. Unfortunately these reports were not available in the west until 1967. [cite journal |last=Zal'tsman |first=G. L. |title=Psychological principles of a sojourn of a human in conditions of raised pressure of the gaseous medium (in Russian, 1961) |journal=English translation, Foreign Technology Division. AD655 360 |date=1967 |location=Wright Patterson Air Force Base, Ohio ]

The term high pressure nervous syndrome was first used by Brauer to describe the combined symptoms of tremor, electroencephalography (EEG) changes, and somnolence that appeared during a 1,189 foot chamber dive in Marseilles. [cite journal |last=Brauer |first=R. W. |title=Seeking man's depth level |journal=Ocean Industry |volume=3 |pages=28–33 |date=1968 |location=London ]

ymptoms

Symptoms of HPNS include tremors, myoclonic jerking, somnolence, EEG changes [cite journal |last=Brauer |first=R. W. |coauthors=S. Dimov; X. Fructus; P. Fructus; A. Gosset; R. Naquet. |title=Syndrome neurologique et electrographique des hautes pressions |journal=Rev Neurol |volume=121 |issue=3 |pages=264–5 |date=1968 |pmid=5378824 |location=Paris ] , visual disturbance, nausea, dizziness, and decreased mental performance.

The susceptibility of divers and animals to HPNS does depend on the individual.

uppressive Measures

It is not likely that HPNS can be prevented entirely but there are effective methods to delay or change the development of the symptoms. [cite journal |last=Hunger Jr |first=W. L. |coauthors=P. B. Bennett. |title=The causes, mechanisms and prevention of the high pressure nervous syndrome |journal=Undersea Biomed. Res. |volume=1 |issue=1 |pages=1–28 |date=1974 |issn=0093-5387 |oclc=2068005 |pmid=4619860 |url=http://archive.rubicon-foundation.org/2661 |accessdate=2008-04-07 ]

Rate of Compression

Utilizing slow rates of compression or adding stops to the compression have been found to prevent large initial decrements in performance. [cite journal |last=Bennett |first=P. B. |coauthors=R. Coggin; M. McLeod. |title=Effect of compression rate on use of trimix to ameliorate HPNS in man to 686 m (2250 ft) |journal=Undersea Biomed. Res. |volume=9 |issue=4 |pages=335–51 |date=1982 |issn=0093-5387 |oclc=2068005 |pmid=7168098 |url=http://archive.rubicon-foundation.org/2920 |accessdate=2008-04-07 ]

Breathing Mixture

It can be avoided by including small amounts of other gases in the mix, such as nitrogen [cite journal |last=Vigreux |first=J. |title=Contribution to the study of the neurological and mental reactions of the organism of the higher mammal to gaseous mixtures under pressure |journal=MD Thesis |date=1970 |location=Toulouse University ] (creating trimix) or hydrogen [cite journal |last=Fife |first=W. P. |title=The use of Non-Explosive mixtures of hydrogen and oxygen for diving |volume=TAMU-SG-79-201 |journal=Texas A&M University Sea Grant |date=1979 ] (hydreliox) [cite journal |last=Rostain |first=J. C. |coauthors=M. C. Gardette-Chauffour; C. Lemaire; R. Naquet. |title=Effects of a H2-He-O2 mixture on the HPNS up to 450 msw |journal=Undersea Biomed. Res. |volume=15 |issue=4 |pages=257–70 |date=1988 |issn=0093-5387 |oclc=2068005 |pmid=3212843 |url=http://archive.rubicon-foundation.org/2487 |accessdate=2008-04-07 ] .

Drugs

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

ee also

* decompression sickness
* hydreliox
* nitrogen narcosis

References


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