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By Andrea Murdock Alpini
Translated by Lara Lambiase (DAN Europe, Diving Medical Officer) AKA Lady Murdock
Header photo by Marco Mori
Everyone would like to run towards their dreams. Touching them is a privilege some people have. Taking them up with both hands is a blessing for just a few. The life wind often blows inconsistently and in many directions. A strong analytic effort is needed in order to understand the right path to follow.
It takes courage to leave behind a wreck. Turning and making the decision that this will be the last time you see her or that you will be close and inside her, these are some hard choices. It sounds like standing at the door saying goodbye to someone dear to you who comes from far away and is going to leave again. To say goodbye means the end and, at the same time, implies a beginning: that your relationship is moving into memory.
The first time I dived down to visit MV Viminale, I knew it would never end in a farewell. Delicate metal sheets embracing me for the first time; her touch and her voice, made up of a long-distance courtship; it all fascinated me so much that I could not help thinking about her: such a charming, elegant ship.
A transatlantic is unique in shape, dimension, history.
The first encounter is never to be forgotten. In just a short while it conveys the whole timbre of what is possible. Your clean-shaved deep-sea observer’s glance cannot stop at the surface anymore. He must see more. “There’s a fracture in everything,” some crack that allows entrance to the inside, a place where delicate worlds are opening or closing.
After one visit, I can say goodbye no longer.
I remember my many, earlier dives, for a full year while I waited for the right moment to meet Viminale. I was able to feel what Penelope, Ulysses’ wife, felt while waiting for her dear husband’s return, much like the endless waits sailors endure as they pass from one harbor to another, the embers of their smokes drifting into the air of the night.
Coming across Viminale’s wreck has been one of the most powerful experiences of my entire life. With my first gaze, I witnessed the past but even so, still longed for the present.
The Future of the Classic
Looking at the Viminale requires a high level of attention. Even though you believe you’re seeing the wreck, you are also watching the ship. At first sight, observers see the wreck, but if they allow themselves to watch carefully and with new eyes, they will see the fascinating Lloyd Triestino ocean liner. Once seen, it’s impossible to be ignored..
You will want to come back, again, again, and again. Your eyes will never grow tired of her beauty and your thirst for knowledge about her will lead you to explore and extend your personal new boundaries. It’s an enchantment: at the exact moment the young girl appears, she begins her transformation into a woman.
Two aspects co-exist, inseparable, but so far apart if you are not able to see.
The first aspect is related to the wreck, which is basically what every person sees while glancing at her; the second aspect represents the future of a classic look. The woman is hidden to the eye, covered by different layers that shaped her, over time.
Looking at the young girl, then the woman appears: the Ship: “She’s a force emerging from the past; she finds her strength in the tradition of love.” Love for whom? For the Sea, who she belongs to since she first floated on the surface of the water until the moment she surrendered and sank, consumed by the ocean’s swells.
I wrote about Viminale last year; my scream of joy in front of the Ship at 107 m/350 ft of depth. The reason I fell in love with this wreck was that, until then I had only seen the young girl, but suddenly the woman appeared to me.
Old alpine climber Walter Bonatti’s hands were thick, but in spite of that, the Alps’ cold wind cut them. Wreckers’ hands test the water, touch very gently, toss roughly or smoothly. Hands, for us wreckers, are more than eyes: they feel, see, and perceive. These hands sometimes plunge as do Amore’s marble fingertips into Psyche, remembering the classic tradition of sculpture. Touch is decisive, but cognitive. Hands clutch, and fingers cling into a pianist’s dance.
When I look at the surface from the bottom of the sea, I sometimes glimpse the far glaze of the surface. Sometimes—not often—it happens that a ray of light fills the distance separating the wreck from life. At that moment my eyes suddenly shine because I am participating in an extraordinary event; the beauty appears in its natural way. Artificial lighting is useless in that moment because your eyes are acclimated to the darkness that surrounds you. In that moment you feel your soul is made whole because you are staring at incomparable natural beauty.
This time, the heavy 45 kg ballast to be thrown on the wreck took place into my cabin van because I felt that it didn’t deserve the cold cargo bed.
Watching it, I felt sure that this was not simply naked iron thrown in the water, but I wanted to paint a love story on its sides, one to accompany it to the sea bed. I traced smooth lines with white enamel on one side, and Lara painted Latin words in capital letters on the opposite side. This was the beginning of something that could not be otherwise; the event that opened a crack in the boundary between what was and what would be.
The very first impact had changed the flow of life into an unexpected and surprising way. I took a brush and began painting on your side THAT’S AMORE, because this is how I go deep into the wreck. Each man and each ship goes through huge storms, the ship’s plank wheel and helmsman make the course, indissolubly together in spite of being visually separated. “Stay with me and the storm will cease”
Like you, none. Never.
Attraction is a magnet that can lure you to insanity.
A year ago, I, along with two dive buddies, entered the engine room of Motonave Viminale. A year later, I along with my personal friend as well as professional photographer, Marco Mori, returned. We had prepared two dive plans. One for 25 minutes of bottom time at a depth 105 m/345 ft in the event of bad visibility and strong flow, and the second for 35 minutes of bottom time at the same depth in the event of good conditions, i.e. clear vis and little flow. We were lucky enough to encounter the second; we had a great dive on the wreck Viminale.
I remember that we had been astonished by the silence that accompanied our dive into the engine rooms of the Italian wreck, the Titanic, as we were surrounded by electric panels, pressure gauges, fire tanks, and ancient lamps that had ceased shining. I will always remember the inner silence broken by thrilling sights, our eyes filled with wonder and happiness as we finned slowly and played out the spool of line to exit with to the main deck. Those memories were the allure that had brought us to the belly of the Viminale. We were careful to move cautiously and to pay attention not to disturb our surroundings.
As my head emerged from the hatch, I could not believe what my eyes saw in front of me. Thanks to the darkness we were coming from and the blackness of the engine room into which we emerged, Palmi seemed more as a deep blue shade reminiscent of the calm sea overhead. The pilot house and the branch lifeboats appeared as sculptures rather than parts of a wreckage.
As we left the engine room at 108 m/352 ft, we moved forward to 90 m/294 ft depth, and I began to brush off the wooden deck with my hand and marvelled at the feeling I received from touching the beauty of the ancient wooden planking. I love iron ships, but the soft touch of wood conjures up for me the feel and scent of a long-ago era. I recollected making the same gesture with my right hand two years previously on the HMS Britannic’s promenade. It is an unforgettable sensation I will carry with me always.
Knowing it was time to ascend, our dive computers were saying that our decompression would require 210 minutes before we could surface, I gazed lovingly one last time from the right side of the pilot house looking toward the bow. I kept all my deco cylinders away from the line and passed an oxygen cylinder to Marco as he was calling “Goodbye,” to Viminale.
Three and a half hours later, we resurfaced, both of us believing this was one of our best dives ever. We were fortunate to be able to see amazing sights, thanks to a fine mix of clear visibility, calm seas, good adrenaline and friendship. A chapter, nay a paragraph in the life of this shipwreck comes to an end yet we both feel that our job is not done. We will be back, again and again. I switched off my dive lamps. We were ready to begin our lift to the surface with the natural light remaining.
Encounters with a woman, a friend or a shipwreck can sometimes shake you up and change your perspective forever. To Viminale I think, “I will meet you again, under the guise that I simply want to talk with you.” Perhaps these thoughts are why I am awake at night, longing to see you again tomorrow. You have become a part of my life. I do not care who had you before me; I am yearning for you. That’s amore. In the end all I want is to dream about you “as I have never dreamed before.”
- Alpini A.M. VIMINALE: TRA BIELLE E PISTONI. SUB UNDERWATER MAGAZINE, # 400, March 2020 (Also see December 2019)
- The Italian Liners Historical Society: Lloyd Triestino
- Viminale Ocean Liner (1937-1943)
- You may also enjoy another of Alpini’s exploration stories: Isverna Cave, Diving An Underground Dacia, InDepth, V 2.5 June 2020
Andrea Murdock Alpini is a TDI and CMAS technical trimix and advanced wreck-overhead instructor based in Italy. He is fascinated by deep wrecks, historical research, decompression studies, caves, filming and writings. He holds a Master’s degree in Architecture and an MBA in Economics for The Arts. Andrea is also the founder of Phy Diving Equipment. His life revolves around teaching open circuit scuba diving, conducting expeditions, developing gear, and writing essays about his philosophy of wreck and cave diving. Recently he published his first book entitled, Deep Blue: storie di relitti e luoghi insoliti.
High Pressure Problems on Über-Deep Dives: Dealing with HPNS
If you’re diving beyond 150 m/490 ft you’re likely to experience the effects of High Pressure Nervous Syndrome (HPNS). Here InDepth’s science geek Reilly Fogarty discusses the physiology of deep helium diving, explains the mechanisms believed to be behind HPNS, and explores its real world implications with über-deep cave explorers Dr. Richard “Harry” Harris and Nuno Gomes. Included is a list of sub-250 m tech diving fatalities.
By Reilly Fogarty
Header image: Original Photo by Sean Romanowski, effects by the team at GUE HQ
There aren’t many technical divers exploring deeper than 153 m/500 ft on a regular basis—the logistical and physiological demands alone make sure of that. The small group of divers who do reach those depths without saturation chambers or other professional accoutrements face a daunting host of new concerns. At these depths, decompression models aren’t as well validated, and dives require precise gas planning and acknowledgement of extreme environmental exposures.
As if decompression illness (DCI) and oxygen toxicity risks weren’t enough, divers must prepare to deal with the possibility that they may get to depth and experience vertigo, confusion, seizures, and a varied list of other neurological maladies—sometimes without warning. These symptoms are the result of high-pressure nervous syndrome (sometimes called high-pressure neurological syndrome) or HPNS. Symptoms of HPNS are highly variable but primarily affect those who descend rapidly to 153 m/500 ft or deeper. HPNS may have played a role in the death of legendary cave explorer Sheck Exley, and it may have caused numerous close-calls in deep cave and wreck explorations. But, the extreme depth required to experience onset has relegated research and education on HPNS to a niche corner of the diving community—one with significant interplay with the commercial saturation diving world and the most extreme sport communities.
The Physiology of Deep Helium Diving
In 1961, G.L. Zal’tsman, who headed the Laboratory of Hyperbaric Physiology, St. Petersburg, Russia, first identified what would eventually become known as high-pressure nervous syndrome. The political climate of the period limited access to his work in the west, so credit for the discovery is often shared with Peter Bennett, D.Sc, who published a paper on the subject in 1965. While politics and international tensions separated them, both researchers described what they called “helium tremors” that occurred during experiments with military subjects. Using gases with the high helium content required to manage narcosis at depth, participants in these studies were observed experiencing uncontrollable muscle tremors upon compression in a chamber.
At the time, it was unknown if this was a function of the helium in their breathing gas or an effect of depth. The term “high-pressure nervous syndrome” originated just a few years after Zal’tsman’s study, when R.W. Brauer identified changes in the conscious states and electroencephalography data from subjects in a chamber dive to nearly 368 m/1,200 ft. In the decades since, several studies further illuminated what we now know as HPNS, primarily as a result of research into deep sea exploration from the 1970s to early 1990s. As it stands now, HPNS is primarily identified by a decreased mental status, dizziness, visual disturbances, nausea, drowsiness, muscle tremors, and seizures in divers rapidly reaching depths of 153 m/500 ft or more, or exploring the extremes of depth closer to 306 m/1,000 ft at any rate of compression while breathing a high helium content gas.
The prevailing theory is that a combination of speed of compression during descent, and the absolute pressure at depth, cause these symptoms. Symptoms are rare during dives above 153 m/500 ft, but dives that exceed that depth, or that reach depth quickly, increase the likelihood of symptom evolution. Symptoms do not appear to correlate to each other, and individual susceptibility is highly variable, which makes predicting onset difficult. Some researchers also theorize that there are two separate conditions caused individually by compression (the symptoms of which diminish at depth) and total pressure (the symptoms of which persist throughout the bottom portion of a dive). This two-part explanation for HPNS symptoms provides some interesting avenues for future research and could help solidify some of the theorized mechanisms underlying the condition, but it has yet to be expanded upon in a significant way.
The mechanism behind HPNS has yet to be proven, but most researchers choose to work upon the basis of a few reasonable theories. The first relies on the compression of the cell membranes in the central nervous system. In this model, the rapid compression of the lipid components of these membranes may alter the function of the inter-lipid structures that facilitate signal transmission within the central nervous system. This change in structure could facilitate hyperexcitability of some nervous system pathways and cause the types of tremors and seizures associated with serious HPNS cases. This membrane compression could also alter the signaling pathways required for motor function and cognition, resulting in confusion and assorted neurological symptoms that sometimes occur in divers with HPNS.
Another model focuses on the role of neurotransmitters themselves, rather than their signaling receptors. The various iterations of this model examine the effects of pressure and varying helium/oxygen exposures on the production or reception of these transmitters. In some ways, this method resembles our understanding of oxygen toxicity mechanisms, which could lead to some interesting interplay between future research projects and the balancing of oxygen and helium exposures at extreme depth. Some of the more promising studies in this area show evidence of NMDA receptor antagonists reducing convulsions in animal models, and describe the effectiveness of increased dopamine release in preventing increased motor activity under extreme pressure in rat models.
A third model focuses on the effect of helium on HPNS risk. This model functions on a yet-unidentified mechanism, but explores the potential distortion of lipid membranes by helium at depth. The data from these studies suggests that high pressure helium—not high hydrostatic pressure—may alter the tertiary structure of protein-lipid interactions and change signaling pathways within the nervous system. Numerous other avenues for research exist in this niche, including projects working on a great number of neurotransmitter related conditions and pre-treatment protocols for HPNS, oxygen toxicity, and possibly related normobaric diseases. Any of these models could prove accurate, but the interplay between the many neurotransmitters makes it most likely that a combination of these models will best illustrate what occurs in-situ.
Experienced firsthand, HPNS is far less academic, but equal parts confounding and terrifying. The variable onset and sometimes ambiguous symptom presentation make it difficult to discern from other conditions, and mild symptoms can be easily written off. By the same token, however, a serious bout of tremors or confusion as a result of a rapid descent to deep water can leave a diver terrified and unable to act. Dr. Richard “Harry” Harris, SC OAM, is a physician and technical diver with years of exploration in deep caves and shipwrecks. His experiences with HPNS mirror that of many. Most often, he’s observed symptoms like trembling hands or loss of coordination that could be attributed to either HPNS or the adrenaline rush of a fast hot-drop from a boat in heavy seas.
On one recent dive to 150 m/490 ft, Harris described becoming temporarily incapacitated on the bottom due to minor tremors, finding himself unable to clip his strobe to the shot line. The symptoms resemble common descriptions of mild HPNS symptoms, but the relatively shallow (in terms of HPNS, at least) depth still gives him pause when he tries to discern the specific cause of the symptoms. Dives past 200 m/656 ft have provided similar conundrums, but Harris has experienced tremors at extreme depths with enough regularity to notice that he is somewhat more susceptible than his regular dive buddy Craig Challen. “This [variation in symptom onset and presentation] has really made me question again the role of the mental state, approach, and perhaps even intentional mindfulness on these symptoms,” explains Harris.
By focusing on gas choices that strike a balance between gas density and the high concentrations of helium that can cause HPNS symptoms, and by descending relatively slowly, Harris has managed to alleviate symptoms on much deeper dives. A recent 245 m/799 ft dive with an intentionally slowed descent gave him none of the same complaints as his rapid descents to shallower water and felt “like a [much shallower] 150 m/490 ft dive.”
It’s worth noting at this point that Harris and Challen are extraordinarily capable and experienced divers, and HPNS is a condition that shouldn’t be taken lightly. Their approach—a combination of conservatism and safety—is likely key to their management of HPNS on extremely deep dives. Other divers, some equally experienced, have not been as fortunate in the past.
Sheck Exley reported a particularly bad case during a dive to 210 m/689 ft, with vision blurred to the extent that he was “looking through small circles with black dots, and started convulsing.” Despite these symptoms, he continued his dive, and proceeded to a maximum depth of 263 m/863 ft. It’s thought that Exley’s eventual death during an attempt to descend past 305 m/1,000 feet in the Mexican Zacatón cave system could have been caused in part by HPNS symptoms exacerbated by narcosis.
Nuno Gomes, a technical diver who holds several Guinness World Records for depth in open water and in caves, has also become intimately acquainted with HPNS, experiencing the following during a world record dive:
“As I descended past 250 m/816 ft, the HPNS set in. At first, relatively mild, then fairly strong. And later on, the symptoms became so extreme that my whole body shook uncontrollably. One other problem was lack of coordination of movement. I felt severely narcosed on my bottom trimix of 3.15/85. It had only a calculated END of 40 m/131 ft. From my experience, a more realistic narcosis level was 78 m/256 ft as calculated using the Total Narcotic Depth (TND). When I reached the tag marked 315 m/1,033 ft at an actual depth of between 322 m/1,056 ft and 323 m/1061 ft, I realized that this was as far as I was able to go. I was not sure that I would be able to return if I went any deeper. At that stage, I was not sure that I would be able to swim up from that depth.”
Gomes’s regular attempts to reach extreme depth made him uniquely prepared to identify symptoms of HPNS as they appeared, but even with his breadth of experience, the effects of the condition could have become lethal if allowed to continue.
Statistically, there just aren’t enough documented cases of HPNS to make for a meaningful analysis, but these incidents can provide a basis for education. The symptom severity and onset variability is enormous, but there are some trends that can be pulled from the stories of Harris, Exley, and Gomes. How to integrate those in your dive plan without meaningful data to back them up, however, falls to personal choice.
Planning for the Future
There are more than a few good reasons not to end this piece with a “how-to” on diving past 153 m/500 ft. With regard to HPNS specifically, the reality is that we just don’t know enough about the mechanisms that cause the symptoms divers experience. What we have is an understanding that high helium content and rapid descents likely contribute to HPNS risk, some people are more susceptible than others, and the symptom presentation is not uniform or predictable. Beyond these fundamental constants, we must piece together what we know from the limited research we do have and the experiences of others.
The data on compression speed appears to be pretty clear: HPNS symptoms may not be entirely preventable, but the risks can be somewhat ameliorated by slowing our descent speeds. There also appears to be an opposing effect between helium and nitrogen content in our breathing gas. This is likely due to changes in the structures of the membranes surrounding our central nervous system caused by helium and other inert gases, requiring divers to balance potential narcotic effects and HPNS risk in gas planning.
Using nitrogen as a protective gas seems counterintuitive, but in some extremely deep dives, adding just 5% nitrogen to a heliox mixture appeared to dramatically reduce HPNS symptoms in divers. However, the extent of practical efficacy remains to be seen. Promising studies researched using hydrogen to minimize HPNS risk, but this avenue of research is prohibitively expensive and logistically challenging due to the inherent fire risk.
The onset of HPNS symptoms also appears to be relatively gradual, although it’s important to recognize that not all data supports this and rapid onset can occur. With slow descent rates and intelligent gas choices, it seems unlikely that divers would experience HPNS severe enough to incapacitate them before they had a chance to turn their dive, but that is not to say that it cannot happen or should be ignored as a real concern. Symptoms of HPNS still haven’t been found to correlate with each other, and not only can new symptoms arise quickly, but also the nature of the ailments means that a diver may not be able to identify symptoms until it is too late to react.
The past decade has failed to provide much in significant data on HPNS as it pertains to recreational divers, certainly almost nothing in comparison to the deep-diving heyday that brought about the COMEX tables and Atlantis projects. Going forward, it seems likely that HPNS will become a greater concern. Technical divers will continue to explore the limits of depth with the widespread adoption of rebreathers, persisting in their search for deeper caves and unexplored wrecks. Hopefully, this ongoing—perhaps even increasing—activity will spur more research into HPNS and the potential interplay between the mechanisms of narcosis and oxygen toxicity. Until then, we’ll have to continue to glean what we can from the data we have and the experiences of the more ambitious among us.
- Naquet, R., Lemaire, C., J.-C. Rostain, & Angel, A. (1984). High Pressure Nervous Syndrome: Psychometric and Clinico- Electrophysiological Correlations [and Discussion]. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 304(1118), 95-102. Retrieved May 21, 2021, from http://www.jstor.org/stable/2396156
- Talpalar, Adolfo. (2007). High pressure neurological syndrome. Revista de neurologia. 45. 631-636.
- Understanding Oxygen Toxicity: Part 1 – Looking Back
- Pearce PC, Halsey MJ, MacLean CJ, Ward EM, Webster MT, Luff NP, Pearson J, Charlett A, Meldrum BS. The effects of the competitive NMDA receptor antagonist CPP on the high pressure neurological syndrome in a primate model. Neuropharmacology. 1991 Jul;30(7):787-96. doi: 10.1016/0028-3908(91)90187-g. PMID: 1833661.
- Kriem B, Abraini JH, Rostain JC. Role of 5-HT1b receptor in the pressure-induced behavioral and neurochemical disorders in rats. Pharmacol Biochem Behav. 1996 Feb;53(2):257-64. doi: 10.1016/0091-3057(95)00209-x. PMID: 8808129.
- Bliznyuk, A., Grossman, Y. & Moskovitz, Y. The effect of high pressure on the NMDA receptor: molecular dynamics simulations. Sci Rep 9, 10814 (2019). https://doi.org/10.1038/s41598-019-47102-x
- High Pressure Neurological Syndrome, DIVER (2012) by Dr. David Sawatzky
InDepth: Diving Beyond 250 Meters: The Deepest Cave Dives Today Compared to the Nineties by Michael Menduno & Nuno Gomes
aquaCORPS:Accident Analysis Report from aquaCORPS #9 Wreckers (JAN95):What happened to Sheck Exley? by Bill Hamilton, Ann Kristovich And Jim Bowden
InDepth: Thoughts on Diving To Great Depths by Jim Bowden
InDepth: Playing with Fire: Hydrogen as a Diving Gas By Reilly Fogarty
Reilly Fogarty is an expert in diving safety, hyperbaric research, and risk management. Recent work has included research at the Duke Center for Hyperbaric Medicine and Environmental Physiology, risk management program creation at Divers Alert Network, and emergency simulation training for Harvard Medical School. A USCG licensed captain, he can most often be found running technical charters and teaching rebreather diving in Gloucester, Massachusetts.
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High Pressure Problems on Über-Deep Dives: Dealing with HPNS
If you’re diving beyond 150 m/490 ft you’re likely to experience the effects of High Pressure Nervous Syndrome (HPNS). Here...