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How Long Will Your Rebreather Scrubber Canister Last?

A U.S. Navy Mark 15 closed circuit rebreather

Are you a child of Lake Wobegon, where according to Garrison Keillor “all the women are strong, all the men are good looking, and all of the children are above average?” If you are, you may be headed for trouble with your rebreather scrubber canister.

Or expressed another way, do you know how long your scrubber canister will last?

Believe me when I tell you, it depends.

Below I explain why the above answer is necessarily evasive, and why the true answer is frustratingly elusive. Canister duration depends on things with which you, as a rebreather diver, are all too aware, and things which you may not have thought about before; namely probability and statistics.

Figure 1. CO2 concentration in canister effluent vs. time. Click for a larger image.

All of what follows is based on canister duration data for a particular rebreather of U.S. Navy interest. Data from other rebreathers are similar qualitatively, but the actual numbers may vary.

In Figure 1, the concentration of CO2 leaving the CO2 absorbent bed within a scrubber canister is plotted as a function of time for five “canister runs” for the same model rebreather. A fresh canister should absorb all the CO2  a diver exhales, leaving CO2-free gas to be inhaled by the diver on the next breath. As the absorbent becomes depleted, the scrubbing process loses efficiency and CO2 begins bypassing the canister. The amount of CO2 being inhaled by the diver begins rising exponentially, as shown in Figure 1.

For this example, canister duration tests were conducted at 70° F, at a fixed depth, with Sofnolime 812™ as the chemical absorbent, and at both a fixed minute volume of gas (representing the simulated diver’s breathing rate) passing through the canister bed, and a fixed rate of CO2 injection representing a fixed work rate and oxygen consumption. Therefore, you would expect results to be very similar from run to run, but Figure 1 shows variation in the amount of CO2 leaving the canister with time.

Figure 2. Fit of the summary data of Figure 1 to a single exponential curve. Click for a larger image.

The average data for the canister curves fit a simple exponential equation fairly well (Figure 2). We were thus justified in using an exponential equation to explore how canister duration might vary from dive to dive. Basically, the equation considered how the amount of CO2 absorbent in the canister, and the rate of CO2 production by the diver, would work together to determine the canister duration, with all else being fixed. The amount of CO2 produced depended on the rate of oxygen consumption, and from the respiratory exchange ratio which determines how much CO2 is produced for a given amount of consumed oxygen.

Fortunately we have data for those variables, in some cases coming from divers using the same rebreather as shown in Figure 1. We have estimates of oxygen consumed during prolonged swims. Most importantly, we have measures of the variability associated with all that data. For instance, Figure 3 shows the bell shaped curve for oxygen consumption data measured by an NEDU researcher during distance swims by Navy divers. We deduced the curve for this exercise from the reported statistics (mean or average, and standard deviation). Similar curves were obtained for the other factors that influence canister duration, except for water temperature. That was assumed constant.
Figure 3. Oxygen consumption bell curve.

We then treated all the known factors and their known variability to a mathematical process called Propagation of Error (H.H. Ku, Notes on the Use of Propagation of Error Formulas, Journal of Res. of the Nat. Bur. Stds., 1966.)

The result was Figure 4 which requires careful study to appreciate what it’s telling us.

If everything about a diver and his diving equipment were “average” then their UBA canister might be expected to follow the white canister breakthrough curve on the far right, identified as P = 0.500. Since that curve represents an average, fifty percent of canisters would be expected to last longer than that curve (fall to the right of the curve) and fifty percent would be expected to fall to the left of it; i.e., to last the same or shorter amount of time. Approximately 16% of the canister breakthrough curves would be expected to fall to the left of the black line identified as P = 0.159, and 2.3% would fall on or to the left of the yellow line (P = 0.023).

Figure 4. Results from the application of propagation of error formulas.Click to enlarge.

Now comes food for thought. What if, as Garrison Keillor says, you’re a child from Lake Wobegon, and are above average in your oxygen consumption? If your dive lasted to the point where the average canister broke through at 0.5% CO2 (about 255 min, white curve intersection with the horizontal blue-green line), then you might be seeing a dangerously high inspired CO2 of 3-4% (vertical blue-green line), depending on how far from average you are.

If you chose to dive for the average time for a canister to reach 2% CO2 (magenta lines), then your actual inspired CO2 could be 7 to 12%, an extremely dangerous CO2 exposure as described in a preceding post.

Keep in mind that in this particular example water temperature was constant. If you dive in a variety of water temperatures your canister duration will vary even more. If your work rate changes widely over the course of a dive, then the canister duration will be essentially unpredictable.

So regarding how long your canister will last on any given dive: Are you feeling lucky?

 

 

 

 

 

 

 

This material was presented by JR Clarke and DE Warkander in a 2001 meeting of the Undersea and Hyperbaric Medical Society. Undersea and Hyperbaric Medicine, 28:81, suppl., 2001.

 

Space Wars

I had a dream, and it troubles me.

I had a dream a couple of weeks ago and awoke knowing I had seen something very disturbing, but couldn’t remember what it was. Then on February 21st I had a lucid dream where I realized that what I was seeing was what I’d seen the previous week. Then I understood why I was disturbed.

It was a scene from a vantage point in space. It was cinematic in quality, big screen, IMAX, at least. I was there.

The troubling part was observing a space vehicle moving up to the space station, then seeing the vehicle suddenly yaw its nose away from the station as if slammed by some powerful but invisible force, followed a split second later by the white paint on the space station charring before my eyes. Not all of it, just the part closest to an out of view source of blistering heat. The curved portion on top of the station was spared; from a thermal radiation standpoint it was very realistic.

Curiously, the station was not the ISS: it was much smaller but the markings on the white paint were clearly U.S.. I overhead two men talking on the coms, supposedly ground control, saying the heart rates of the station occupants soared.

It woke me, and I realized the entire dream sequence had lasted about five seconds, at most. It must have been the sauerkraut from the night before.

But what struck me as startling was the news article the next morning about the Chinese preparing for war in space. http://freebeacon.com/dia-director-china-preparing-for-space-warfare/

To quote, “Beijing is developing missiles, electronic jammers, and lasers for use against satellites…The Chinese, as well as the Russians, are also developing space capabilities that interfere with or disable U.S. space-based navigation, communications, and intelligence satellites.”

Suddenly, the thought of either space-based or ground-based attacks on manned vehicles or space stations becomes a frightening possibility.

Then tonight I read that a NASA notebook computer containing codes for controlling the Space Station was stolen.

http://washington.cbslocal.com/2012/03/01/nasa-laptop-stolen-with-command-codes-that-control-space-station/

“These incidents spanned a wide continuum from individuals testing their skill to break into NASA systems, to well-organized criminal enterprises hacking for profit, to intrusions that may have been sponsored by foreign intelligence services seeking to further their countries’ objectives,” Martin said. “Another attack involved Chinese-based IP addresses that gained full access to systems and sensitive user accounts at the Jet Propulsion Laboratory in Pasadena, Calif.”

We tend to think of space as a neutral environment where brave souls put their lives at risk to be part of man’s push away from our planet. It is an environment for scientific pursuit. Of course we have raised a generation or two on images of space battles where humans are fighting to preserve humanity. There is lots of death and destruction, but it is heroic in scope and detail. If death can be glorious, then dying to protect Mother Earth from Klingons is a glorious way to die.

But what I saw in those five seconds of searing imagery left me with a profound sadness. I had witnessed, so to speak, the end of our honeymoon in space. Man’s evil nature was reaching way beyond our stratosphere.

I put no stock in dreams, at least not  my own. But that particular dream did serve to increase my awareness of the not-so-subtle signs that man is determined to extend his malevolent reach into what was once considered hallowed ground; the firmament, the very heavens we have for so long dreamed of reaching.

And now we would spoil it.

 

 

 

 

 

 

A Flight to DeFuniak Springs

Affordable, high definition cameras are opening up a world of sporting video to those who can’t compete with the pros. For aviators, we get to share our passion, the beauty of flight!

I recently borrowed a GoPro camera and gave it a try. The flight in the Piper Arrow was short, 29 nm, from the new airport at Panama City (ECP) to DeFuniak Springs. The sky was spectacular and the air was fresh from the north but at a mercifully pleasant temperature for February (low seventies in °F).  The air was a little turbulent below 2500 feet, explaining the slight bumpiness of the video at low altitude.

After takeoff, climbing to smooth air, I circled over the cypress and hardwood-lined Choctawhatchee river which heads south from southern Alabama to empty into the Choctawhatchee Bay near Destin and Ft. Walton in the Florida Panhandle.  As shown below, that river drains some of the best scuba and cave-diving springs in Florida, including Morrison Spring, featured in the previous post.

Locally, there seems to be some nonchalance about the spelling of Defuniak, De Funiak or DeFuniak. The French care of course, but the locals don’t. Surprisingly, the town was not named after a French trader with the Choctaw Indians. DeFuniak Springs was named after Fred de Funiak, the first president of the Pensacola and Atlantic Railroad who envisioned DeFuniak Springs as a resort for northern visitors.

A pilot can appreciate that in the video the approach to landing in DeFuniak Springs was not as well aligned as it should have been. I had fallen victim to the visual illusion spoken of in the blog posting Killer Optical Illusions – Size Does Matter.

I usually fly into runways between 150 and 200-feet wide, including current or former military runways and the airport at Panama City. It had been a year since I’d flown into DeFuniak’s narrow 60-foot wide runway, and even though I circled the field twice I still found myself too close-in on downwind (flying parallel to the landing runway, in the opposite direction). That, plus a strong tailwind on base (perpendicular to the runway) put me past the point where I would normally line up for landing.

Over-correcting close to the ground can be fatal due to an event called the stall spin accident. It occurs when aircraft are flown incorrectly close to the ground during that potentially fateful turn to “final”, trying to line up with the runway. Being mindful of that I kept my speed up and corrected no more than necessary to find my way to the runway.

I didn’t realize it at the time, but my wife was parked opposite from my intended landing spot watching the approach. I’m glad that, all things considered, it turned out well. At least it drove home my previous point that “Size Matters”.

Technical details: This HD video was taken from the cockpit of a Piper Arrow. A GoPro camera filmed the action. Royalty-free music was generated automatically by Cyberlink PowerDirector 10 with SmartSound technology.

I See Dead People – Sort Of

The exit to the Morrison Springs cave. (photo credit: ZoCrowes255)

The young man in a swimming suit was lying lifeless at the bottom of a fissure on the floor of Morrison Springs, a popular underwater cave in Walton County, Florida. If his eyes had been open, he would have been staring straight up at me. But mercifully, his eyes were shut, as in sleep.

My diving buddies from the Georgia Tech Aquajackets dive club and I were breathing air from scuba tanks at about 110 feet sea water. We were in a portion of the cave that received no indirect light from the cave opening. Without the cave lights in many of the diver’s hands there would have been total darkness.

Who knew that on my second so-called “open water” dive I would find myself deeper than 100 feet in a cave, using the dispersed light from my buddies’ dive lights to examine a very fresh looking corpse? He looked to be about our age, late teens, high school or college age. A rock outcropping hid his body from about mid-hip level down. But the top portion of a bathing suit, his lean stomach, chest, and boyish-looking face and head was plainly visible.

There must have been some current at the bottom of the crevice because his brown hair was waving gently, being the only sign of motion from the deathly pale white boy with closed eyes, waiting patiently to be recovered to the surface.

I and the other divers stretched our arms and shoulders as far into the crevice as we dared, reaching towards the young man, hoping we could grab onto some part of his body. But it was futile – he was at least a foot out of our reach. Finally, checking our dive watches, we saw it was time to swim toward the cave entrance and start our ascent.

Since there was no scuba gear on him he must have been a free-diver, a breath-hold diver who entered the cave then passed out and sank to the deepest, most inaccessible portion of the cave. As I and the other divers rose along the limestone borders of the cave I watched the darkness surround the young man’s cold body once again. I felt lonely, almost as if I could feel his spirit’s loneliness.

As I reached the surface I turned to the closest diver, removed my regulator from my mouth, and panted, “How are we going to recover that body?”

His response stunned me.

“What body? That was no body – that was a Navy 6-cell flashlight!

How could it be? I would have signed a sworn affidavit to the police describing everything I had seen, in detail, just as I’ve reported it to you many years later. The visual details, the textures, the emotions will not leave me.

But they were not real.

As for why that happened, the only thing I can assume is that for a nineteen-year old novice diver, descending in the dark to 110 feet, in a cave, might be just a bit more than the diver’s mind is prepared for. The nitrogen in air is narcotic if found in high enough concentration, so I was undoubtedly suffering from nitrogen narcosis. Plus, at the time the entrance to the Spring was macabre, with a large photo of a diver with his back filleted open by a boat propeller, and signs prominently displaying warnings of the large number of fatalities in the cave from poorly trained and equipped divers exceeding their limits.

My mind was prepared to witness tragedy, and the normally mild nitrogen narcosis of 110 feet may have  been just the trigger needed for a vivid hallucination.

I have had no hallucinations since then, from diving or anything else, except for one medical procedure reported on in this blog. But what remains remarkable to me was my absolute conviction that what I had seen in that cave was real. Consequently, I now know very well  that what people testify as being real, whether they are diving or not, may in fact be only imagined.

How Much is Too Much? (Carbon Dioxide – The Diver’s Nemesis)

The amount of carbon dioxide (CO2) that can be safely inhaled by rebreather divers is a continuing point of conjecture, and vigorous argument. Unfortunately, the U.S. Navy  Experimental Diving Unit has confused that issue, until recently.

A non-diver might wonder why a diver should inhale any CO2. After all, the air we breathe contains only a small fraction of CO2 (0.039%). A rebreather is best known for emitting no bubbles, or at most very few bubbles depending on the type of rebreather. It does that by recirculating the diver’s breath, adding oxygen to make up for oxygen consumed by the diver, and absorbing the carbon dioxide produced by the diver. The CO2 scrubber canister is vital to keeping the diver alive. As pointed out in the first post in this series, carbon dioxide is toxic; it can kill.

A CO2 scrubber  keeps the recirculating CO2 levels low by chemically absorbing exhaled CO2. However, the scrubber has a finite lifetime – it can only absorb so much CO2. Once its capacity has been exceeded, CO2  passing through the canister accumulates exponentially as the diver continues to produce CO2 from his respiration.

The question rebreather divers want answered is, “How much of that bypassed CO2 can I tolerate?” As we’ve discussed in previous posts, 30% CO2 can incapacitate you within a few breaths. I can personally verify that if you’re exercising you may not notice the effect 7% CO2 has on you, until you try to do something requiring coordination. I’d equate it to the effect of drinking too many beers. There is little controversy about CO2 levels of 5-7% being bad for a diver.

For levels below 5-7% CO2, the U.S. Navy has not been real clear. For instance, 2% CO2 is the maximum CO2 allowed in diving helmets. If CO2 were to climb higher the diver would most likely feel a need to ventilate the helmet by briefly turning up the fresh gas supply to clear CO2.

Since at least 1981, NEDU has defined the scrubber canister breakthrough point in rebreathers as 0.5% CO2. That means that at some point, which varies with CO2 injection rate, ventilation rate, water temperature, and grain size of CO2 absorbent, CO2 begins leaking past the canister, not being fully absorbed during its passage through the canister. Once that leakage starts, the amount of CO2 entering the diver’s inspired breath rises at an ever increasing rate unless work rate or other variables change. By the time the CO2 leaving the canister has reached 0.5%, the canister has unequivocally “broken through”.

I pointed out in my last post that even 0% inspired CO2 may be too much for some divers when they are facing resistance to breathing. And all rebreathers are more difficult to breathe than other types of underwater breathing apparatus because the diver has to force his breath through the rig’s scrubber canister and associated hoses. The deeper the dive the denser the breathing gas and the worse breathing resistance becomes.

In free-flow diving helmets like the old MK 5, and the short-lived MK 12, the diver did not breathe through hoses and scrubber canisters. But those helmets had a high dead space and to keep helmet CO2 at tolerable levels a fresh gas flow of 6 actual cubic feet per minute (acfm; 170 liters per minute) was required. The U.S. Navy allowed up to 2% CO2 in the helmet because 1) the helmets did not have a high work of breathing and 2) due to simple physics the helmet CO2 couldn’t be kept very low.

For rebreathers, none of the above apply. A high breathing resistance is inevitable, at least compared to free-flow helmets, and once CO2 starts rising there is nothing you can do to decrease it again, short of stopping work.

In 2000, NEDU’s M. Knafelc published a literature review espousing that the same limit for inspired CO2 which applies in helmets could be used in rebreathers. Nevertheless, in 2010 NEDU’s D. Warkander and B. Shykoff clearly demonstrated that in the face of rising inspired CO2 concentrations work performance is reduced, and blood levels of CO2 rise, in some cases to dangerous levels. More recent work by the Warkander and Shykoff duo have extended those studies into submersion, however those reports are not yet publicly available.

As a result of both physiological theory and confirmatory data in young, physically-fit experimental divers, NEDU has not relaxed the existing definitions of scrubber canister breakthrough, 0.5% PCO2. Furthermore NEDU will adhere to the current practice of using statistical prediction methods to define published canister durations, methods which are designed to keep the odds of a diver’s rebreather canister “breaking through” to no more than 2.5%, comparable to the odds of decompression sickness following Navy multi-level dive tables. Details of this procedure will be explained in later postings.

 

Knock Yourself Out (Carbon Dioxide – The Diver’s Nemesis)

Most rebreather divers start off their diving career with open-circuit diving; that is, with scuba. And some of them pick up bad habits. I happen to be one of those divers.

With scuba you start the dive with a very limited amount of air in your scuba bottle. New divers are typically anxious, breathe harder than they have to, and blow through their air supply fairly quickly. More experienced divers are relaxed and enjoy the dive without anxiety, and thus their air bottles last longer than they do with novice divers.

So early in a diver’s experience he comes to associate air conservation with a sign of diver experience and maturity. When you are relaxed and physically fit, and your swimming is efficient, your breathing may become extraordinarily slow. Some call it skip breathing — holding your breath between inhalations.

I was once swimming among the ruins of Herod’s Port in Caesarea, and my dive buddy was a Navy SEAL. I started the dive under-weighted, so I picked up a 2000 year old piece of rubble and carried it around with me as ballast. In spite of the very inefficient style of swimming which resulted, my air supply still lasted longer than that of my SEAL buddy.

At first I was annoyed that I had to end the dive prematurely, but then I began to feel somewhat smug. I had used less air than a frogman.

As a physiologist I knew that I may well have been unconsciously skip breathing, which would have raised my arterial carbon dioxide level, potentially to a dangerous level. But all ended well, and I could not help being glad that I was not the one to call the dive.

It is important for rebreather divers to understand that they don’t have to be breathing elevated levels of carbon dioxide to run into physiological problems with carbon dioxide. It’s the carbon dioxide in your arterial blood that matters. It can render you unconscious even when you’re breathing gas with no carbon dioxide at all.

MK 16 rebreather diver

Normally the body automatically ensures that as you work harder, and produce more carbon dioxide in your blood stream, that you breathe more, forcing that CO2 out of your blood, into the lungs, and out through your mouth. It works like an air conditioner thermostat; the hotter it gets in the house, the more heat is pumped outside. In other words, arterial and alveolar CO2 levels are controlled by automatic changes in ventilation (breathing.) In fact you can predict alveolar levels of CO2 by taking the rate at which CO2 is being produced by the body and dividing it by the ventilation rate. This relationship is called the Alveolar Ventilation Equation, or in clinical circles, the PCO2 Equation.

Normally, CO2 production and ventilation is tightly controlled so that normal alveolar and arterial CO2 is about 40 mmHg, mmHg being a unit of so-called partial pressure. 40 mmHg of arterial CO2 is safe. [One standard atmosphere of pressure is 760 mmHg, so ignoring the partial pressure of water vapor and other gases, a partial pressure of 40 mmHg of CO2 is equivalent to exhaling about 5% carbon dioxide.]  

When a diver is working hard while breathing through a breathing resistance like a rebreather, as ventilation increases respiratory discomfort goes up as well. For most people, when the respiratory discomfort gets too high, they quit working and take a”breather”. But there are some divers who hate respiratory discomfort, and don’t mind high levels of arterial CO2. We call these people CO2 retainers.
Navy experimental deep sea divers; photo credit: Frank Stout

As an example, I once had as an experimental subject a physically fit Navy diver at the Naval Medical Research Institute during a study of respiratory loading. The test was conducted in a dry hyperbaric chamber under the same pressure as that at 300 feet of sea water. The experimental setup in the chamber looked somewhat like that in the figure to the right although the diver I’m talking about is not in this photo.

The diver was exercising on the bicycle ergometer while breathing through a controlled respiratory resistance at 300 feet in a helium atmosphere. The diver quickly learned that by double breathing, starting an inspiration, stopping it, then restarting, he could confuse the circuitry controlling the test equipment, thus eliminating  the high respiratory loading.

As he played these breathing pattern games my technician was monitoring a mass spectrometer which was telling us how high his expired CO2 concentration was going. The exhaled CO2 started creeping up, and I warned him that he needed to cut out the tricky breathing or I’d have to abort the run.

The clever but manipulative diver would obey my command for a minute or so, and then go back to his erratic breathing. He joked about how he was tricking the experiment and how he felt fine in spite of the high CO2 readings.

That was a mistake.

When you’re talking, you’re not breathing. Since his breathing was already marginal, his end-tidal CO2, an estimate of alveolar CO2, shot up in a matter of seconds from 60 to 70 and then 90 mmHg, over twice what it should have been. When my technician told me the diver’s exhaled CO2 was at 90 mmHg, I yelled “Abort the run”. But the diver never heard that command. He was already unconscious and falling off the bike on his way to the hard metal decking inside the hyperbaric chamber.

The diver thought he was tricking the experiment, but in fact he was tricking himself. Although he felt comfortable skip breathing, he was rapidly pedaling towards a hard lesson in the toxicity of carbon dioxide.

Keep in mind, this diver was breathing virtually no carbon dioxide. His body was producing it because of his high work level, and he was simply not breathing enough to remove it from his body.

In upcoming posts we’ll look at what happens when inspired CO2 starts to rise, for instance due to the failure of a carbon dioxide scrubber canister in a rebreather. I already gave you one example in the CO2 rebreathing study of my first post in this series. There’s lots more to come.

 

 

 

 

 

 

 

 

 

 

 

 

 

Carbon Dioxide – The Diver’s Nemesis Pt. 1 (Meduna’s Mixture)

Of all the gases humans excrete, the most bountiful, and arguably the most deadly, is exhaled carbon dioxide.

There is a forgotten bit of American medical history that reveals the bizarre features of the toxicity of carbon dioxide. In 1926, before the advent of modern psychiatric medications, some American psychiatrists began experimenting with the use of inhaled carbon dioxide for the treatment of schizophrenia and psychoses. At the time, there were no effective treatments other than electroshock.

Dr Ladislas J. Meduna

One of the most successful of these researchers was Dr Ladislas J. Meduna, a Professor of Psychiatry at the University of Illinois College of Medicine in Chicago.

High levels of carbon dioxide (CO2) did in fact have some success in treating schizophrenia, but it also produced Out of Body (OBE) and seemingly spiritual experiences. The following text is quoted from a book called Carbon Dioxide Therapy. A Neurophysiological Treatment of Nervous Disorders, published in 1950 and authored by Meduna.Meduna administered by mask between 20 and 30 breaths of a gas mixture of 30% CO2, 70% O2. From pg. 22 of his book we find,

“Any attempt to define the sensory phenomena during CO2 anesthesia, in terms of dream, hallucination, illusions, etc., would be futile. The actual material would support any hypothesis. Some of the sensory phenomena would direct us to define them as hallucinations. Some of these phenomena are felt by the patients as “real dreams”; others obviously are dreamy repetitions of real events in the past or of past dreams. I believe therefore that any classification of these phenomena in terms of dream or hallucination would be not only meaningless, but directly misleading; the patient is not “sleeping” in the physiological sense, nor is he in the state of consciousness which we usually assume to be present in true hypnagogic hallucinations.”

click to enlarge

“One subject, after 20 respirations of the gas, reported seeing a “bright light, like the sun.”

“It was a wonderful feeling. It was marvelous. I felt very light and didn’t know where I was. For a moment I thought: ‘Now isn’t that funny. I am right here and I don’t know whether I am dreaming or not.’ And then I thought that something was happening to me. This wasn’t at night. I was not dreaming. And then it felt as if there were a space of time when I knew something had happened to me and I wasn’t sure what it was. And then I felt a wonderful feeling as if I was out in space.”

“After the second breath” — reported a 29 year-old healthy female nurse who had taken a treatment – “came an onrush of color… then the colors left and I felt myself being separated; my soul drawing apart from the physical being, was drawn upward seemingly to leave the earth and to go upward where it reached a greater Spirit with Whom there was a communion, producing a  remarkable, new relaxation and deep security. Through this communion I seemed to receive assurance that the petite problems or whatever was bothering the human being that was me huddled down on the earth, would work out all right and that I had no need to worry.”

“In this spirituelle I felt the Greater Spirit even smiling indulgently upon me in my vain little efforts to carry on by myself and I pressed close the warmth and tender strength and felt assurance of enough power to overcome whatever lay ahead for me as a human being.”

Meduna summarized that preceding case by stating, “In this beautiful experience we can discern almost all the constants of the CO2 experience: (1) color; (2) geometric patterns; (3) movement; (4) doubleness of personality; and (5) divination or feelings of esoteric importance.”

Meduna went on to admit that “Not all of the sensory phenomena experienced by the patients are of celestial beauty and serenity. Some of them are horrifying beyond description.”

In 1971, Chris Lambertsen, M.D., Ph.D., from the University of Pennsylvania School of Medicine, and considered to be the father of special warfare diving by Navy SEALS, published a careful examination of the physiological consequences of the Meduna mixture. He found that inhalation of 30% CO2 in oxygen would cause unconsciousness and convulsions within 1-3 min. The precipitating event for loss of consciousness seemed to be a catastrophic increase in the acidity of the blood due to the large amount of carbonic acid produced by the CO2 inhalation. This raises the possibility that the experiences noted by Meduna were caused by pre-convulsive events within the brain.

Since then the medical community has deemed carbon dioxide “treatments” as not only dangerous but ineffective compared to modern psychiatric medication. Meduna’s mixture is no longer used.

While at the Naval Medical Research Institute, I was my own research subject in a study of the effects of rebreathing  CO2 concentrations up to 8%. That was a carbon dioxide concentration that some Navy SEALS had claimed could be tolerated without impairment.

The simplest scrubber canister in the simplest rebreather, Ocenco M20.2

I was not under water, but riding a stationary bicycle ergometer in the laboratory, simulating breathing on a closed-circuit underwater breathing apparatus (in diving vernacular, a rebreather.) Although oxygen was being added as I consumed it, there was no carbon dioxide scrubber (a container of carbon dioxide absorbing material), so the test was examining what happens when a scrubber canister is no longer functioning properly. At 7% inspired  CO2 I stopped the exercise, feeling a little abnormal. However, I was surprised at how unimpaired I seemed to be; that was, until I attempted to dismount the ergometer. I almost fell and needed help removing myself from the bicycle to a chair.

The single-minded and simple-minded task of exercising had hidden a growing central nervous system impairment. Like someone intoxicated with alcohol, I could not judge my level of impairment until a task requiring some coordination was required.

So we see that high levels of carbon dioxide intoxication can lead to profound disturbances of the central nervous system. In upcoming posts we’ll see how elevated carbon dioxide levels and the control of respiratory ventilation can interact to put rebreather divers at risk.

Much of the above is from a nonfiction book project currently under review. The working title for the book is “Collected Tales of the Spiritual and Paranormal.”

 

Google Noodling and other Technological Pleasures

I am easily bored.

Fortunately, I’m also easily entertained. In fact I have no trouble at all entertaining myself, especially if it’s at the expense of new technology. Especially if the technology has big names attached to it like Facebook and Google.

Now don’t misunderstand me. I love and use both Facebook and Google, a lot. But sometimes they just crack me up.

For example, there is a new Facebook app allowing you to leave a message behind after you die.

What a clever idea! No need for séances, or readings by psychic mediums. All you have to do is plan ahead for what you want to say, write it down, then tell your family and trusted friends to inform FB that you are indeed deceased. Voila, you get to have the final words, the last laugh, to have your say without being interrupted.

Of course, if your final thoughts as your life ebbs away are about changing your mind, or regretting what is about to be said, well, there’s simply nothing to be done. The cat will be out of the bag.

And you better not wake up in the morgue chiller if you’ve finally told the world what you think about your in-laws, or the wife, or your boss. You may not be technically dead anymore, but for all practical purposes, you are. Or you’ll wish you were.

But I can’t help thinking how much fun it would be to plan an after-life revenge on someone I consider despicable, but don’t wish physical harm on them. Let’s say their collected body of lies, fabrications and falsehoods have earned them a stint in Hell, but you’re not sure Hell really exists. Or perhaps you’re impatient.

Imagine then a Facebook farce where you reveal that you buried a  small fortune in gold, which is now worth a large fortune, at a vacant lot at some particular GPS coordinates. Of course, you’d not mention that the vacant  lot now had a McMansion built on it, by the very person from whom you seek after-life revenge.

Photo credit: hercules-online.com

Imagine the look on your archenemy’s face when people start gathering in front of his  home with GPS units, and backhoes. Do you think that would make him nervous?

I realize there are some logical inconsistencies with such a fabricated story, but I think you can count on the  ability of most people to dismiss logic if there is believed to be a fortune to  gain.

So thank-you Facebook; no more need for haunting and ectoplasm. Isn’t technology great?

The next technology that really is fun is Google’s screening of  any and all words in your Gmail. There is a way to play games with it —  I call it Google Noodling.

Photo credit http://www.catfishingtipstoday.com/catfish-noodling/

If you’re from the south you should know what noodling is. But if  you’re not, I’ll explain. Noodling is the reaching of bare hands into a catfish hole and hauling out a feisty catfish. It’s rough and tough fishing without a  pole, line, or hook. Your hand is the hook, and you hook the fish by feel through their mouth or gills. It’s a blood sport that Roman gladiators would  have enjoyed.

So, where does Google come in?

Both my wife and I have Gmail accounts, and I noticed when my wife  sent an email to me that there were certain subject relevant advertisements that accompanied that email. We all know by now, or should, that Google  computers read every word of our messages, and uses its proprietary algorithms to select ads that might be of interest to both sender and recipient. When one of those ads are clicked on, money goes into Google’s pocket. So much for privacy.

Enter into the mix my somewhat contrarian mind. I concocted an email from my wife to me, where the scenario is that I’m on travel and she is  complaining about certain female maladies that are irritating her. Well, faster than you can say itch, an ad popped up on the email after it was sent that offered over-the-counter antifungal remedies.

Well, since the ersatz wife had started a supposedly discrete discussion with her husband, I responded in a like manner, but of course with gender-appropriate words thrown in.

Bingo! Ads for things we commonly see on TV appeared in a flash.

Are we sure there is no panel of underpaid girls in Hong Kong intercepting our emails, laughing their butts off while pushing the Cialis ad button? I don’t know; I’m not convinced.

So I decided to run a test. Posing as my wife again, I concocted a fantastic email that combined a set of mixed-gender complaints, as if the person sending the email were a fully developed and functioning hermaphrodite. Then I hit the send button and waited for the first ads to show up. I checked my account — message received, but no ads. I checked her sent mail — message  sent, but no ads showing on the sent mail.

I had my hands in Google’s gills. Their snooping computers were mystified! How delicious, I thought; Google was stumped.

And then it happened. A few minutes later when I rechecked the sent mail it had an ad for a treatment for, of all things, constipation.

Google had the last laugh. Sure, their algorithms were getting ambiguous messages about gender, so the previously targeted ads could not be sent. But I hadn’t thought about the lowest common denominator among the sexes. And after spinning a few million compute cycles thinking, the Google computers decided on a sure course of action.

Those clever devils!

I suppose the message is, new technology is being spawned at a dizzying rate, designed to provide us “features” we never thought we needed, and to keep its inventors in the black, financially. But at the same time these innovations are fodder for the imaginative mind who sees the value in a good laugh. Count me in as one of those minds.

 

 

The Green Flash and Inspiration

Some say it is serendipity. In reality, maybe it is just the human ability to increase awareness once your attention has been attracted. For example, you’re thinking about buying a black Subaru when you suddenly notice how many black Subarus are on the road.

Photo credit, Mila Zinkova.

I had been thinking of late about the Green Flash, a rare optical phenomenon that I experienced once, years ago, on the Pacific shore at Monterey California. It was memorable not only because of its surprising appearance, and its brevity, but because it was one of the most monochromatically pure and intense visions I’ve experienced.

I have since watched many sunsets over the water, trying to witness again what I saw in Monterrey. I recently watched for it from the air, flying towards the Gulf of Mexico as the sun set. I have watched from an elevated pavilion at St. Andrews State Park in Panama City, Florida.

So far, nothing has come even close to matching what I once saw. That is one of the givens for the Green Flash; witnessing it is oftentimes considered a once-in-a-lifetime event.

The closest I’ve come recently was seeing a greenish tint on the top part of the sun as it appeared to be half way below the horizon. My wife confirmed what I was seeing, but the brilliant flash of emerald green I saw in Monterey has eluded me.

And then like the black Subaru, I saw the Green Flash again recently in a rented 2007 movie, “Pirates of the Caribbean: At World’s End.”

But it was not the same. The Green Flash appeared in the movie like the flash from a nuclear explosion, stretching from one side of the screen to the other. There were even sound effects.

That was not the Green Flash I know.

I don’t blame Hollywood for its hyperbole. After all, I don’t think the beauty of what I once saw would convey well on the silver screen, or the TV screen. In fact photographs, such as the ones above or on the Internet fail to capture the essence of it. The brilliance of color from the flash is otherworldly — it cannot be easily reproduced.

I chuckled at the point in the Pirates of the Caribbean script when the statement is made that the Green Flash means a soul is coming back from the dead.

Master Gibbs

“Ever  gazed upon the green flash, Master Gibbs?”

“I reckon I’ve seen my fair share. Happens on rare occasion; the last
glimpse of sunset, a green flash shoots up into the sky. Some go their whole lives without ever seeing it. Some claim to have seen it who ain’t. And some say—”

“It signals when a soul comes back to this world, from the dead!”

I’m as intrigued with the paranormal as the next person, but I know what 18th century pirates could not know; the green flash is a physical phenomenon, not a metaphysical one.

According to some bloggers, and Wikipedia, the purported association between souls and the Green Flash was promulgated  by Jules Verne through his fiction. Supposedly Verne claimed it to be an old Scottish legend in his 1882 novel Le Rayon-Vert, according to which, one who has seen the Green Ray is incapable of being “deceived in matters of sentiment,” so that “he who has been fortunate enough once to behold it is enabled to see closely into his own heart and to read the thoughts of others.”

Others have misquoted the passage to say that “if one were to peer in the light of the green flash they would gain the power to read the very souls of other people they met.” But that quotation is a no truer translation from the French.

As I said, Verne’s passage is a fictional myth. So, one good fiction leads to another. And of course a little Hollywood computer graphics and sound effects makes it that much better.

But what inspired me to write about the Green Flash is the resemblance, in my mind at least, between the Green Flash and inspiration.

Inspiration comes to me, and you as well I suspect, in a flash. It may be rare, but like the Green Flash it is all so clear, like a lucid dream; an “aha” moment. It is a revelation, perhaps.

Flashes of inspiration have power; they cause things to happen.  Flashes of inspiration have led me to write poetry, science fiction, and non-fiction. Some would call it the writer’s Muse: I just call it that flash of inspiration that seemingly comes from outside me.

Through a flash of lucidity, inspiration caused me to invent a new type of rebreather underwater breathing apparatus. It also caused me, at a young age, to hop on a tiny 50 cc Honda motor-scooter and ride from Atlanta to almost my destination, Kansas City. (50 cc Honda scooters are not really built for long distance cruising, but that didn’t stop me from trying and almost succeeding.)

Inspiration has caused me to raise my hands to the heavens and feel the very presence of God.

Inspiration has propelled me to pull a union thug out of a courtroom and tell him I forgave him for the assault that broke my jaw. Like the cross-country motor scooter ride, not all inspired events would be considered sane except by the person inspired. But they can be life-changing.

Unlike the Green Flash, inspiration can come anytime, anywhere. But like the emerald flash of the setting sun, inspiration can occur when you least expect it.

Both are gifts to be treasured for a lifetime.

Killer Optical Illusions — Size Does Matter

A discrepancy between what you see and what you expect to see can prove fatal.

In graduate school at Florida State University I drove a motorcycle between Tallahassee, FL and my home in Thomasville, GA almost every day of the week, an 80-mile roundtrip. I seldom took the heavily traveled direct route. One alternative route took me through the boonies along a road that apparently rarely saw a motorcycle. One summer day, somewhere between Miccosukee and Metcalf I approached a ramshackle, rusting tin-roofed house, and out of the yard came bounding a dog which apparently lived for the excitement of chasing cars.

As bikes go, a Honda CL 350 was not a large bike. It was a combination road/trail bike called a Scrambler. It was smaller than even a 500 cc Honda, and much smaller than a car. That disparity in size caused the charging dog to misjudge his distance from me. He was falling prey to an optical illusion: objects that are smaller than you anticipate seem farther away than they actually are.

As a pilot, and knowing something about firearm marksmanship, I can admire in retrospect the animal’s uncanny ability to properly lead and zero in on a fast moving target. He was on a collision course with my 346 lb bike traveling at highway speed. Of course, when intercepting hard steel with something as fragile as a skull, it is not a good idea to complete the interception.

I well remember the image of that dog, mouth open, tongue lolling happily to the side of his maw, seeming to relish the chase of a moving vehicle. And then in an instant his expression changed when he realized that he was actually going to catch a moving vehicle.

I don’t think he had thought through the consequences of completing his intended attack.

He applied his brakes —- front legs fully and stiffly extended, toes digging into the asphalt. But he was too late; his momentum carried him headfirst into the mid-section of the bike as our paths crossed.

His car chasing days were over.

We humans might smugly think we are not so easily confused by an optical illusion based on expected sizes and shapes. After all, we are highly intelligent creatures. But we would be wrong in our smugness.

There is a new airport in the Florida Panhandle built in the middle of millions of slash pine acres. It was a land donation designed to assist the land owners with developing sylvan land into valuable real estate. Unfortunately the real estate crash has stymied development around the airport, so an aircraft flying at night into the field which boasts a long 10,000 foot runway, sees only blackness around the airport. What results is the so-called black-hole illusion.

The black-hole illusion applies to unusually long runways lit up at night and surrounded by impenetrable blackness. The runway at ECP (Panama City) is about twice as long as the usual runways used by general aviation aircraft, and at 10,000 feet is far longer than the runway at the previous Panama City airport (PFN). The almost overpowering visual illusion is that you are closer to the runway than you actually are, and that you are considerably higher than you are in reality. On final approach the unwary pilot gets the impression that he is too high, and must push the nose of the aircraft down. In fact, nothing could be further from the truth. A pilot has to be on his game to resist the potentially deadly optical illusion.

In a black-hole situation, it is critical to fly by the aircraft instruments, with the altimeter being one of the most important. When in the grips of the black-hole illusion I find it very easy to fly the “pattern”, the rectangular visual approach that eventually leads you to the runway, at too low of an altitude. Now I am aware of the trap, but I still have to concentrate on the instruments and ignore the visual cues from the humongous runway. I also find new pilots flying my aircraft into the field for the first time falling into the same trap. Looks can be very deceiving.

A simulated black hole approach to a runway. Orbiter imagery from Guleit.com

Boeing engineers found through their night approach research that during a black hole approach flown solely by reference to the view out the windscreen, pilots will have an almost overwhelming urge to fly too low as they approach the airport. The result of such action is likely to be impact with the ground two to three miles from the runway. Details of that discussion, relying heavily on geometry, are aptly given in the following aviation news item from 2000. http://www.avweb.com/news/airman/182402-1.html.

Airline transport pilots using autopilots to fly an Instrument Landing System guided approach to the runway seldom have to worry about visual illusions. But even they can be fatally fooled when going visual. There have been at least two commercial crashes caused by the black-hole optical illusion; Alitalia Flight 4128and VASP Flight 168. (For more details, click on the Alitalia and VASP links.)

A depiction of a black hole feeding on stars and gas.

As we learn about astronomical black holes, we realize they destroy all things in their grip. However, much closer to home are personally destructive phenomena that result from nothing more than visual trickery, a vicious mental confusion between actual and perceived sizes of airport runways, and as it turns out, even between motorcycles and cars.