Isolation Tank

isolation tank by jon han

An isolation tank is a lightless, soundproof tank inside which subjects float in salt water at skin temperature. They were first used by John C. Lilly in 1954 to test the effects of sensory deprivation. Such tanks are now also used for meditation and relaxation and in alternative medicine.

The isolation tank was originally called the sensory deprivation tank. Other names for the isolation tank include flotation tank, John C. Lilly tank, REST tank, sensory attenuation tank, and think tank.

John C. Lilly, a medical practitioner and neuro-psychiatrist, developed the flotation tank in 1954. During his training in psychoanalysis at the US National Institute of Mental Health (NIMH), Lilly commenced experiments with sensory deprivation. In neurophysiology, there had been an open question as to what keeps the brain going and the origin of its energy sources. One hypothesis was that the energy sources are biological and internal and do not depend upon the outside environment. It was argued that if all stimuli are cut off to the brain then the brain would go to sleep. Lilly decided to test this hypothesis and, with this in mind, created an environment which totally isolated an individual from external stimulation. From here, he studied the origin of consciousness and its relation to the brain.

Peter Suedfeld and Roderick Borrie of the University of British Columbia began experimenting on the therapeutic benefits of flotation tank usage in the late 1970s. They named their technique ‘Restricted Environmental Stimulation Therapy’ (REST). In the original tanks, people were required to wear complicated head-masks to breathe underwater, but the mask detracted from the isolation experience. The tight fit of the mask seal around the face and the retention strips wrapping around the back of the head were uncomfortable in long sessions. The constant hissing of the air valves and bubbling of exhaust air out of the mask prevented the possibility of silence. The faceplate of the mask was typically solid black for visual isolation, but then the tank user needed help entering and leaving the isolation tank since the mask blinded them.

In newer tanks, epsom salt is added to the water in the tank to increase the density of the water so that the subject floats with the face above the water. And, since the ears are submerged when the subject is in a relaxed position, hearing is greatly reduced, particularly when ear-plugs are also used. When the arms float to the side, skin sensation is greatly reduced because the air and water are the same temperature as the skin, and the feeling of a body boundary fades. The sense of smell is also greatly reduced, especially if the water has not been treated with chlorine. The growing number of commercial float tanks has brought increased regulation of disinfection. In Europe, a bathing water standard requires automated chlorination. There is also some doubt about ozone safety because of the closed air space. Generally, users of isolation tanks enter the pool nude. Although a swimsuit may be worn, the elastic material of a tight-fitting suit can create uncomfortable compressed stress points on the skin during the session. Due to the high epsom salt content, the water is minimally changed, and all users are expected to shower, wash with soap, and rinse clean prior to entering the tank to extend the water life as long as possible. Bathing is again needed after a session to remove excess epsom salt from the skin.

Most isolation tanks use a circulating surface skimmer, cartridge filtration, and disinfection means, including ultraviolet sterilization and chemicals to keep the water free of microbes and sediment, though this is turned off during a session to keep the isolation space as quiet as possible. A ring heating system can be used around the outer walls of the tank to warm the water so that it rises up the outside edges of the pool, travels towards the center, and then sinks under the tank user. This very slow water convection flow helps to keep the user centered in the middle of the pool, without them floating to the side and bumping into the walls of the small tank during long float sessions. However, when the floater is still, the small waves caused by breathing also tend to center them in the solution regardless of a convection effect.

Isolation tank construction and plumbing is typically all-plastic (glass reinforced resins are common). High quality flotation tanks may use acrylic or medical stainless steel which is impervious to the strong salt solution and more importantly the disinfectants. Unsealed stone and concrete surfaces can also be damaged by dissolved Epsom salt splashed or dripped outside the tank, due to the dried salt recrystallizing and opening up cracks and fissures. Epsom salt is not corrosive in the way sodium chloride (table salt) is but chlorine can attack some surfaces such as marble.

A therapeutic session in a flotation tank typically lasts an hour. For the first forty minutes, it is reportedly possible to experience itching in various parts of the body (a phenomenon also reported to be common during the early stages of meditation). The last twenty minutes often end with a transition from beta (alert) or alpha (relaxed) brainwaves to theta (drowsy), which typically occurs briefly before sleep and again at waking. In a float tank, the theta state can last for several minutes without the subject losing consciousness. Many use the extended theta state as a tool for enhanced creativity and problem solving. The more often the tank is used the longer the theta period becomes.

Spas sometimes provide commercial float tanks for use in relaxation. Flotation therapy has been academically studied with published results showing reduction of both pain and stress. The relaxed state also involves lowered blood pressure and maximum blood flow. Floating can be passive or active, depending on the purpose. For relaxation, one simply floats and ‘clears the mind.’ Active floating has many different techniques. One may perform meditation, mantras, self-hypnosis, utilize educational programs, etc. The idea of active floating is that, when the body is relaxed, the mind becomes highly suggestible and any action taken during these states will enter the information into the sub-conscious. Flotation therapy may be used to complement other body work and healing methods. More extreme uses of the tank involve the subject taking varying doses of psychedelics; such as LSD, psilocybin mushrooms, DMT, ketamine, or cannabis and spending prolonged periods in the tank (up to tens of hours) at a time, an approach pioneered by John C. Lilly himself—though he claims to have tried LSD in the tank only prior to 1964, while the psychedelic was still legal. This is regarded by commercial float centers as extremely dangerous behavior and is prohibited.

Flotation tanks take advantage of an atavistic ability that seems to be common to all humans to relax when floating at a comfortable temperature. The temperature is that which allows natural heat generation to escape without the need for muscle action to raise body temperature in homeostasis. The floating posture, usually the supine position (although the prone position with chin supported on elbows is recommended for pregnant women), allows all the postural muscles to relax. The water pressure on the immersed skin is lower than the blood pressure and thus blood flow continues in skin capillaries. This is in contrast to normal bed rest where local contact pressure inhibits blood flow requiring regular adjustment of posture. When people cannot adjust their posture in bed, e.g. in some illnesses, bed sores can result. When floating there is no tendency to adjust posture and a person can float immobile for many hours. The natural tendency of the body in the floating posture at the correct temperature is to dilate the blood vessels, reducing the blood pressure and maximizing blood flow. The brain activity normally associated with postural muscles is reduced to a minimum. In this state, which we can call the floating state, natural endorphins are released reducing pain. Lactic acid removal is accelerated. Flow in the lymphatic system is increased.

Perceived stress can be correlated with increased levels of cortisol (a stress hormone) and in flotation therapy there is a natural tendency for cortisol to be reduced. For this reason, floatation therapy is one of the few noninvasive techniques available to manage stress when it is a factor in reducing a person’s ability to cope with normal life. Flotation therapy is a fast technique in this respect. The Swedish research was based on 40 minute float sessions. This compares well with other management techniques such as long vacations. There are many similarities with the age-old long, hot bath, the differences being that in floatation therapy the temperature is maintained at the correct level and the bath is large enough to float without touching the sides.

It has recently been discovered that there is a secondary effect which is important to flotation therapy. Magnesium is absorbed through the skin due to natural molecular diffusion. This tends to correct magnesium deficiency. Magnesium is absorbed from the diet but in many areas of the world, over-cropping (exhausting the fertility of soil) without adequate replacement of magnesium makes the normal diet low in magnesium. The body naturally optimizes the levels of magnesium, so there is no overload effect from floating in the salts for extended periods.

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