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This article appeared in the April 1990 issue of Code One Magazine.
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 James Whinnery unexpectedly found himself in the frozen foods section of a local grocery store. ''Since I was there," recalls Dr. Whinnery, "I decided to pick up a half gallon of vanilla ice cream." The story gets better. "There were frozen desserts in flat freezers on the right side of the aisle and TV dinners in uprights on the left," says Whinnery. "I didn't want to grab just any brand of vanilla or to reach down in there and pick up some Neapolitan by mistake.
"The trouble was that I couldn't move my hands or turn my head to look into the freezer. In the meantime, I was being uncontrollably propelled down the aisle past the ice cream section. It was a frustrating experience."
Whinnery's shopper's nightmare lasted only a few seconds. It was interrupted by a loud beeping sound and a bright flashing light. As he returned to consciousness, he knew he had to disable these annoyances by pressing a button to his right (just where the ice cream was a moment earlier). Though he was now aware, he was still unable to turn his head or move his arm to get to the button.
Pressing the button marked the end of a period of incapacitation, a period that began when Whinnery lost consciousness pulling nine g's in a human centrifuge. Whinnery gives his side of the ordeal as he replays a video tape of it on a VCR in his office at the Naval Air Development Center in Warminster, Pennsylvania. Whinnery is the chief aeromedical scientist at the Air Vehicle and Crew Systems Technology Department. His office is a few yards away from the largest human centrifuge in the world.
In the tape, Whinnery is asked by an operator about any vision loss he may have experienced during the run. "I don't know where I am," replies a seemingly euphoric Whinnery. "I thought I was in the grocery store." This particular episode of a g-induced loss of consciousness (or g-LOC) is one of almost 800 that Whinnery has collected over the last fifteen years.
Most of these g-LOC episodes were coincidental with fighter-pilot g training on the centrifuge at the Naval Air Development Center and at Brooks AFB in San Antonio. Recent work at the NADC has led to new insights into how the brain deals with extreme conditions. As it turns out, this research has implications that go far beyond testing g suits or training pilots to perform better straining maneuvers.
Unconsciousness has not always been a subject of study in centrifuge labs. Until recently, it merely marked the limit of high-g research. Simply put, an experiment ended when the subject passed out. Unconsciousness was viewed as a barrier, and the purpose of research was to come up with new methods to push the barrier back--to make the human system less susceptible to a high-g environment. g suits, straining maneuvers, tilting seats, and positive-pressure breathing systems are the results of this approach. Each one increases a subject's g tolerance in measurable amounts.
Measurable is a key concept in science. Science requires quantification. Events that are not measurable to human senses or to devices that extend our senses often get ignored. They fall outside the realm of science. Unconsciousness, an event that involves a loss of the senses, presents an inherently sticky topic for science. Approaching g-LOC from the unconsciousness side is a gutsy move. But it's a move that seems to be paying off in recent high-g research.
Instead of asking what can be done to prevent or delay the loss of consciousness, researchers are now asking what can be done to regain consciousness. Unconsciousness, then, becomes a starting point rather than a barrier. It becomes a topic for investigation (and reflection) instead of something to avoid or ignore.
In many ways, g-LOC episodes defy classification. For one thing, there are just too many variables, not the least of which are the physiology of the test subject and the individuality of the responses. It is difficult to predict how a particular person will respond to a high-g environment. Every g-LOC episode, however, goes through two relatively distinct periods. The first is a period of absolute incapacitation in which the subject is, by all definitions of the term, unconscious. The second is a period of relative incapacitation--a sort of semi-consciousness. During this period, the subject appears to be responsive, but actually isn't.
The absolute incapacitation period begins when the subject loses consciousness. It is relatively easy to detect: the eyes roll back in the head, and the subject slumps down in the seat, as he or she releases the control stick (which slows the centrifuge back to 1 g). The period of absolute incapacitation can last from two to forty seconds. The average time is twelve seconds. In most cases (about seventy percent), the subject experiences convulsions of varying severity.
Convulsions during g-LOC episodes can be so severe that the pilot will activate or deactivate cockpit controls. In a recent g-training run, a pilot's flailing motions disconnected the hose to his g suit. Whinnery suspects that a large proportion of aircraft accidents involving high-performance fighters are related to g-LOC.
The convulsions during g-LOC last about four seconds and come at the end of the period of absolute incapacitation, just before the pilot appears to be responsive again. These convulsive movements are often incorporated into the dream sequences recalled by subjects. One of Whinnery's favorite tapes illustrates this. In the tape, a young pilot makes a single backwards motion with his head and upper body as he jerks his hands upward and back. Afterwards, he recounts his short dream:
Operator: What happened?
Pilot: I was fishing.
Operator: For what?
Pilot: For bass.
Operator: Where were you
Pilot: Lake Calaveras [a lake near Brooks AFB, where the centrifuge
run took place].
Operator: Go on.
Pilot: I had about a five-or six-pound bass on my line. I felt a struggle like I had just caught a fish.
The incorporation of movements into the dream sequences indicates that the dreams also occur when the movements occur — at the end of the period of absolute incapacitation. According to Whinnery, the dreams are usually vivid and in color.
During the second period — the period of relative incapacitation — subjects appear to be conscious and aware. However, they have no control over intentional body movements. The subjects are confused and frozen. The period ends when voluntary movement returns, and the loud beeper or flashing light can be turned off. This second period lasts, on average, sixteen seconds. It can be as short as one second and as long as one and a half minutes.
The overall period of incapacitation averages almost thirty seconds — a menacingly long period of time to be flying out of control in a jet aircraft.
Menacing in a less measurable way is the frequent denial of having lost consciousness. Watching these g-LOC tapes gives the impression that a majority of fighter pilots are habitual liars. In a typical g-LOC episode, a loud beeper comes on just after the pilot's head drops and eyes roll back. He shakes a few times and eventually comes to. He slowly moves his head back to its original position and sits there for a while, apparently oblivious to the loud beeping. After a time, he turns it off. When an operator asks him about any vision loss he may have experienced, he replies that he got a "little tunneling" (a slight loss of sight that precedes a g-LOC). The reply is strange, considering the guy just extinguished a beeper that indicates he passed out completely.
"I did?" is a common response when the operator informs the pilot that he did in fact pass out.
This response, which on the surface appears to be an unwillingness by the pilot to admit that he was out of control, can be explained by the physiology of memory. (Ego may also play a role.) The brain takes about seven seconds to place an experience in memory. This delay has been confirmed in experiments on the NADC's Dynamic Flight Simulator, which allows the pilots to control the g forces experienced in the centrifuge. When pilots review tapes of sorties in which they lost consciousness, they can recall the entire sortie up to a point where they assume they lost consciousness. However, the point is always about seven seconds before they actually lost consciousness. In other words, the tape shows seven seconds of controlled flight beyond that point.
So the point in time when consciousness is lost never makes it to memory. It is lost in that seven-second gap. Being the temporal animals that we are, our minds come up with explanations (called confabulations) to fill in the gap. Nothingness is tough to deal with, jaws drop when subjects view tapes of their own g-LOC episodes.
During g-LOC, neurons in the brain's cortex are deprived of blood. They go into what Whinnery calls an inhibited state about seven seconds into this deprivation. The neurons take care of themselves by shutting down, by not communicating with other neurons.
"I feel strongly that unconsciousness is a protective mechanism," says Whinnery. "It puts you flat fast so the heart is at the same level as your brain. The convulsive movements are similar to anti-g straining maneuvers. Muscles contract to get the blood back into the central circulation so it can get to the brain. The cardio-respiratory control centers, which are lower in the brain stem, lower than those centers of consciousness, keep working right through unconsciousness. It's a wonderful defense mechanism we have evolved. Basically, the body goes through a series of protective maneuvers to prevent damage to the integrity of the brain.
"Dreaming protects you psychologically from the unknown," continues Whinnery, "from the void you have experienced, from the physical closeness to death. The experience can be overwhelming."
Accounts of g-LOC episodes share features with accounts of people who were brought back to life after being declared clinically dead. Tunneling vision, a frequent occurrence in these accounts, is one of the first indications of blood loss to the head. Subjects often experience euphoria upon regaining consciousness. Some have had out-of-body experiences. Whinnery has found that the length and the intensity of the experience is related to the amount of time the blood is kept from returning to the brain.
When subjects experience g-LOC, they are asked to complete a questionnaire. The last question asks for a description of the episode. Last December, Whinnery received an exceptional account from a fighter pilot who had experienced g-LOC for the first time:
It was a small form of death. Awakening from it was like being spit from the abyss, swung bodily back into consciousness, like being dumped into a vat of ice water from a warm deep sleep. No, not warm; it was empty, nothingness, a bottomless abyss.
Consciousness did not return whole. It came in fits and starts, dragging itself from the edge of darkness in lurches of drunken convulsions.
The first awareness was complete confusion. Where am I? What's going on? Who am I? The lack of self-identity brought a formless fear with it. There was light and dark and sound, but no form, no reason. Then, as my gaze wandered over the enclosure, I began to recognize things: the screen of the flight simulator, the arc of the inside wall, the stick, the throttle. I knew what these things were, and there was less anxiety with the knowledge.
As my consciousness lunged and reeled towards reality, another feeling arose. I had a mission, something I must do to complete my job. This sprung from some hidden crevice where it had been crushed out of sight. The light. The beeping. They had been in my view, but for how long? It seemed like a long time. Only now they impinged on my senses.
My first impulse to move, to take action was a surprise, a shock. My arm wavered crazily. After three beeps, I shut off the light. I now knew what I was supposed to accomplish next. I had to focus on four numbers. Just as the fourth number disappeared, my identity returned. I knew who I was. What a relief, a release from tension.
The sensation of loss of time was now very strong, and would remain so for hours, fading gradually as if to step back from the abyss. I had been recreated after an eternity of nothing. I had memories of a time before, but they were separated from now by the chasm of thatinfinity.
As normalcy returned, the only manifestation of the passage through the void was the coldness of the memory of nothingness, a psychic gap. A shudder came as nothingness was reexamined. The feeling of loss was strong. Even now, nine hours later, the memory is no less potent. It carries with it an anxiety, an ill-defined scar, and the aura of melancholy. I wonder if mere repetition can quell this feeling? The natural aversion to the unknown wrestles with a macabre curiosity. Can one voluntarily revisit the abyss and remain convinced that he is wholly the same?
High-g research at the Naval Air Development Center is producing more than vivid accounts of g-LOC episodes. The research has direct applications in auto-recovery systems in which detecting unconsciousness plays a primary role. Such a system would involve monitoring a combination of physiological parameters (these can include electrical activity in the brain, blood flow to the brain, head movement, respiration, hand contact with the stick). But which parameters should be measured? What are the most effective combinations? What are the least intrusive? These are some of the questions of current research.
Whinnery is also investigating methods for reducing the time a pilot is incapacitated from g-LOC. "Remember that a pilot can appear to be in control even though relatively incapacitated," notes Whinnery. "That makes it extremely difficult to come up with an effective system, one that won't get turned off because it produces too many false alarms."
Perfecting these systems will require a better understanding of unconsciousness. "From our research, we're getting that better understanding," says Whinnery. "We're learning what is necessary for a person to be conscious. What brain functions must be lost to be unconscious. We've learned a lot, but we still have a lot to learn."
Brain research involving healthy subjects has some inherent dangers. Nerve tissue is fragile, and damage to it is usually permanent. Few researchers have the opportunity that Whinnery and his staff have. "Our situation is unique," says Whinnery, "because the benefits in crew protection favorably balance the risks associated with this research. High-g environments are part of daily operations. We must do whatever we can to improve safety, to lower the risks. In doing this, we can't afford to ignore unconsciousness."
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