High pressure nervous syndrome

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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).[1] 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.[1][2] Zal'tsman also reported on helium tremors in his experiments from 1961. Unfortunately these reports were not available in the west until 1967.[3]

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.[4]


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

The susceptibility of divers and animals to HPNS does depend on the individual.[1]

Suppressive 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.[1][6]

Rate of Compression

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

Breathing Mixture

It can be avoided by including small amounts of other gases in the mix, such as nitrogen[8] (creating trimix) or hydrogen[9] (hydreliox)[10].


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

See also


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Brubakk, A. O. (2003). Bennett and Elliott's physiology and medicine of diving, 5th Rev ed. United States: Saunders Ltd. p. 800. ISBN 0702025712. Unknown parameter |coauthors= ignored (help)
  2. 2.0 2.1 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. Check date values in: |date= (help)
  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. Check date values in: |date= (help)
  4. Brauer, R. W. (1968). "Seeking man's depth level". Ocean Industry. London. 3: 28–33. Check date values in: |date= (help)
  5. Brauer, R. W. (1968). "Syndrome neurologique et electrographique des hautes pressions". Rev Neurol. Paris. 121 (3): 264–5. PMID 5378824. Unknown parameter |coauthors= ignored (help); Check date values in: |date= (help)
  6. Hunger Jr, W. L. (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. Unknown parameter |coauthors= ignored (help); Check date values in: |date= (help)
  7. Bennett, P. B. (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. Unknown parameter |coauthors= ignored (help); Check date values in: |date= (help)
  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. Check date values in: |date= (help)
  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. Check date values in: |date= (help)
  10. Rostain, J. C. (1988). "Effects of a H2-He-O2 mixture on the HPNS up to 450 msw". Undersea Biomed. Res. 15 (4): 257–70. ISSN 0093-5387. OCLC 2068005. PMID 3212843. Retrieved 2008-04-07. Unknown parameter |coauthors= ignored (help); Check date values in: |date= (help)

it:Sindrome nervosa da alta pressione no:Høytrykks nervøst syndrom