High Pressure Nervous Syndrome: Research Summary

5 min read · 21 May 2026

The causes, mechanisms and prevention of the high pressure nervous syndrome is a 1974 review by Hunger Jr and Bennett on neurological effects associated with exposure to high pressure. The subject matters because pressure can alter nervous-system function, shaping the risks and practical limits of deep diving and hyperbaric work.

What is high pressure nervous syndrome?

High pressure nervous syndrome, often abbreviated HPNS, describes a group of neurological and behavioural effects associated with exposure to very high ambient pressure. It is a pressure-related problem of deep exposure, distinct from decompression illness, which arises from changes in inert gas pressure during ascent and decompression.

Its significance is both medical and operational. Changes in coordination, sensation, cognition or other aspects of nervous-system function can affect a diver’s ability to perform tasks and respond safely in a demanding environment. The precise experience can vary with exposure conditions and the individual.

How can pressure affect the nervous system?

At depth, the surrounding pressure increases, and the body is exposed to a physical environment unlike ordinary surface conditions. Pressure effects on the nervous system are not simply a matter of mechanical compression: the physiology of nerve-cell membranes, electrical signalling and the effects of breathing gases are all relevant areas of inquiry.

Gas composition and pressure can influence how the nervous system functions. This is one reason deep-diving physiology examines the interaction between the environment, breathing mixtures and human performance, rather than treating depth as an isolated variable. HPNS belongs to this wider effort to understand how the body responds to extreme pressure.

Why does the syndrome matter to divers and clinicians?

Deep-diving operations may require sustained attention, accurate movement and reliable judgement. Neurological effects that disturb these abilities can complicate a task even when they do not resemble a conventional injury. For diving physicians and hyperbaric clinicians, recognizing pressure-related symptoms also helps distinguish them from other causes of altered function.

HPNS is therefore connected to several broader concerns in diving medicine: exposure planning, human performance, gas selection and the safe conduct of work under pressure. Scientific divers and technical teams also need to understand that physiological responses can constrain operations, not just equipment or available time.

What concepts help explain research on HPNS?

Work addressing the causes, mechanisms and prevention of HPNS sits at the intersection of physiology and operational diving. These key concepts help frame the subject:

Ambient pressure: the surrounding pressure to which the diver is exposed, which rises with depth.
Neurological function: the nervous system’s role in sensation, movement, coordination and cognition.
Breathing-gas effects: the way pressure and gas composition may interact with physiology and performance.
Exposure conditions: depth, duration and the broader circumstances of a pressure exposure.
Prevention: approaches to reducing risk through understanding mechanisms and managing exposure, rather than assuming one measure addresses every situation.

Considering these factors together is important because a symptom or performance change may reflect more than one influence. Research in this area asks how pressure-related effects arise, what physiological processes may be involved, and how knowledge of those processes can inform safer deep exposure.

How does the topic fit into diving research?

The 1974 review belongs to the development of diving and hyperbaric research concerned with the limits of human function under pressure. HPNS is one of several distinct physiological challenges that become important when people work or conduct research in high-pressure environments. Its focus on causes, mechanisms and prevention reflects the need to connect basic physiology with practical questions about exposure.

It is useful to distinguish this subject from other pressure-related problems. Decompression illness concerns injury associated with decompression and gas bubbles; nitrogen narcosis concerns changes in function associated with breathing certain gases at depth. These issues may all matter in diving, but they describe different mechanisms and should not be treated as interchangeable.

Frequently asked questions

What does HPNS stand for?

HPNS stands for high pressure nervous syndrome, a set of neurological effects associated with exposure to very high ambient pressure.

Is HPNS the same as decompression illness?

No. HPNS is associated with high-pressure exposure, while decompression illness is associated with decompression and processes involving inert gas. They are distinct diving-medicine concerns.

Who should assess possible pressure-related symptoms?

Symptoms during or after diving require appropriate medical assessment. A diving-medicine physician should be consulted for concerns about pressure-related neurological effects.

Citation details

Title: The causes, mechanisms and prevention of the high pressure nervous syndrome
Authors: Hunger Jr, WL; Bennett, PB
Year: 1974
Published in: Undersea Biomedical Research 1974 Mar;1(1):1-28. Review
Identifiers: PMID 4619860
Repository record: Rubicon Research Repository, handle 123456789/2661

This page is an original summary written by the Rubicon editors from the publication’s bibliographic record. It does not reproduce the paper, its abstract or its data; consult the publication itself for its methods and findings.