High Pressure Neurological Syndrome
Introduction
High Pressure Neurological Syndrome (HPNS) is a condition observed in deep-sea divers descending beyond 150 meters, marked by disturbances in neurological function, psychological status, and EEG activity. The intensity of its symptoms depends on how quickly the pressure increases and the maximum hydrostatic pressure experienced.[1]
Etiology
High Pressure Neurological Syndrome is thought to arise due to elevated atmospheric pressure affecting the central nervous system (CNS), resulting in heightened CNS excitability[2]. This increased excitability is primarily linked to NMDA receptor activity, highlighting a promising area for further scientific investigation.[3]
Epidemiology
Comprehensive epidemiological data on high-pressure neurological syndrome (HPNS) remains limited or unavailable.[4]
Pathophysiology
Multiple hypotheses have been proposed to explain the mechanisms behind HPNS. Susceptible physiological factors may involve shifts in membrane phospholipid fluidity, modifications in ion channel behavior, and impairments in the function of receptors, enzymes, and various proteins when exposed to high-pressure environments.[1]This compressive force may impact molecular processes associated with volume expansion, thereby altering the function of transmembrane proteins, membrane receptors, and ion channels.[5]
Similarly, anesthetic gases might reduce the symptoms of HPNS by reversing pressure-induced changes and helping to restore the normal structure of central nervous system cell membranes, a phenomenon known as the pressure reversal effect of narcosis.[6]
Research has explored the involvement of several neurotransmitters in the development of HPNS, such as gamma-aminobutyric acid (GABA), dopamine, serotonin (5-hydroxytryptamine [5-HT]), acetylcholine, and N-methyl-D-aspartate (NMDA).[2]
Under hyperbaric conditions, serotonin may contribute to increased excitability within the spinal cord. In high-pressure environments, rats display behaviors similar to serotonin syndrome—marked by changes in mental status, agitation, myoclonus, heightened reflexes, shivering, and tremors—indicating a possible role of the 5-HT1a receptor subtype in this response.[2]
Recent findings by Aviner et al. propose that selective modulation of different presynaptic voltage-dependent calcium channels (VDCCs), as well as channels in the soma and dendrites under high-pressure conditions, may significantly influence synaptic transmission—an effect closely linked to the development of HPNS.[1]
Treatment
- Although complete prevention of HPNS is not currently possible, various strategies are available to delay its onset or alter the severity of its symptoms.[2]
- Reduction of Compression Speed
- Modification of the Breathing Gas Mixture
- Pharmacological Treatment
Differential Diagnosis
Deep-sea diving is linked to several medical conditions, such as oxygen toxicity, inhalation of contaminated breathing gases, nitrogen narcosis, high-pressure neurological syndrome (HPNS), decompression sickness, and carbon dioxide buildup caused by increased gas density.[7]
Complications
These symptoms can greatly hinder a diver’s ability to perform effectively underwater, increasing the likelihood of errors in judgment or unsafe actions.[8]
References
- ↑ 1.0 1.1 1.2 Jain KK. High‐pressure neurological syndrome (HPNS). Acta neurologica scandinavica. 1994 Jul;90(1):45-50.
- ↑ 2.0 2.1 2.2 2.3 Jain KK. High‐pressure neurological syndrome (HPNS). Acta neurologica scandinavica. 1994 Jul;90(1):45-50.
- ↑ Bliznyuk A, Hollmann M, Grossman Y. High pressure stress response: involvement of NMDA receptor subtypes and molecular markers. Frontiers in Physiology. 2019 Sep 27;10:1234.
- ↑ Buzzacott P, Schiller D, Crain J, Denoble PJ. Epidemiology of morbidity and mortality in US and Canadian recreational scuba diving. Public Health. 2018 Feb 1;155:62-8.
- ↑ Talpalar AE. High pressure neurological syndrome. Revista de neurologia. 2007 Nov 1;45(10):631.
- ↑ Kot J. Extremely deep recreational dives: the risk for carbon dioxide (CO 2) retention and high pressure neurological syndrome (HPNS). International Maritime Health. 2012;63(1):49-55.
- ↑ Kot J. Extremely deep recreational dives: the risk for carbon dioxide (CO 2) retention and high pressure neurological syndrome (HPNS). International Maritime Health. 2012;63(1):49-55. BibTeXEndNoteRefManRefWorks
- ↑ Bennett PB. Physiological limitations to underwater exploration and work. Comparative Biochemistry and Physiology Part A: Physiology. 1989 Jan 1;93(1):295-300.