High-pressure nervous syndrome (HPNS – also known as high-pressure neurological syndrome) is a
neurological and
physiological
Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
diving disorder
Divers face specific physical and health risks when they go underwater with scuba or other diving equipment, or use high pressure breathing gas. Some of these factors also affect people who work in raised pressure environments out of water, for e ...
which can result when a
diver descends below about using a breathing gas containing
helium. The effects experienced, and the severity of those effects, depend on the rate of descent, the depth and the percentage of helium.
"Helium tremors" were described in 1965 by
Royal Navy physiologist
Peter B. Bennett
Peter B. Bennett (12 June 1931 – 9 August 2022) was the founder and a president and CEO of the Divers Alert Network (DAN), a non-profit organization devoted to assisting scuba divers in need. He was a professor of anesthesiology at Duke Unive ...
.
electroencephalography
Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex ...
(EEG) changes, and somnolence that appeared during a chamber dive
A diving chamber is a vessel for human occupation, which may have an entrance that can be sealed to hold an internal pressure significantly higher than ambient pressure, a pressurised gas system to control the internal pressure, and a supply of ...
in Marseille.
Symptoms
Symptoms
Signs and symptoms are the observed or detectable signs, and experienced symptoms of an disease, illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormali ...
of HPNS include tremor
A tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving oscillations or twitching movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, fa ...
s, myoclonic jerk
Myoclonus is a brief, involuntary, irregular (lacking rhythm) twitching of a muscle or a group of muscles, different from clonus, which is rhythmic or regular. Myoclonus (myo "muscle", clonic "jerk") describes a medical sign and, generally, is ...
ing, somnolence, EEG changes, visual disturbance, nausea, dizziness, and decreased mental
Mental may refer to:
* of or relating to the mind
Films
* ''Mental'' (2012 film), an Australian comedy-drama
* ''Mental'' (2016 film), a Bangladeshi romantic-action movie
* ''Mental'', a 2008 documentary by Kazuhiro Soda
* ''Mental'', a 2014 O ...
performance.[
]
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 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 and remain regardless of the time spent at that depth. All effects are completely reversible on ascent to shallower depths.[
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.][
The effect of dissolved helium on an embedded trans-membrane channel has also been studied by molecular modeling tools. Those suggest that helium might cause substantial lipid membrane distortion. The high hydrostatic pressure itself has a less damaging influence on the membrane, reducing molecular volumes, but leaving the molecular boundary intact.
]
Prevention
It is likely that HPNS cannot be entirely prevented but there are effective methods to delay or change the development of the symptoms.[
Slow rates of compression, or adding stops to the compression, have been found to prevent large initial decrements in performance.][
Including other gases in the Heliox helium–oxygen mixture, such as nitrogen (creating trimix) or hydrogen (producing hydreliox), suppresses the neurological effects.][ None are currently in use for humans.
]
In popular culture
HPNS is a plot point in the 1989 James Cameron
James Francis Cameron (born August 16, 1954) is a Canadian filmmaker. A major figure in the post-New Hollywood era, he is considered one of the industry's most innovative filmmakers, regularly pushing the boundaries of cinematic capability w ...
film '' The Abyss.''
See also
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*
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*
*
References
{{DEFAULTSORT:High-Pressure Nervous Syndrome
Diving medicine
Underwater diving safety
Underwater diving physiology