Those wanting a second shot at life - if and when technology allows it - look to industrial gases for ultra-cold preservation.

According to Alcor Life Extension Foundation, world leader in its field, cryonics is the science of using ultra-cold temperature to preserve human life, with the intent of restoring good health when technology becomes available to do so.

The ultra-cold temperatures are achieved using liquid nitrogen; the liquefied gas preserves the body for however long it will take before the preservation process can be reversed, and the person restored to full health.

More than 100 people have been cryopreserved since the first case in 1967, and more than one thousand people have made legal and financial arrangements for cryonics with one of several organisations, usually by means of affordable life insurance.

Cryonics is based on three key elements which theoretically would mean that in time, a human body could be restored to its former glory, even though it has been medically labelled as dead.

Those involved in the science of cryonics consider that life can be stopped and restarted if its basic structure is preserved – human embryos for example are often preserved for years at a time, at temperatures that completely stop the chemistry of life.

Secondly, adding high concentrations of chemicals called cryoprotectants to cells permits tissue to be cooled to very low temperatures with little or no ice formation. The state of no ice formation at temperatures below -120°C is called vitrification.

Finally, methods for repairing structure at the molecular level can now be foreseen – the emerging science of nanotechnology will eventually lead to devices capable of extensive tissue repair and regeneration, including repair of individual cells one molecule at a time. This will mean that any damage caused by the preservation process will be fixable.

The sooner a cryonics team can get to a body after legal death has been pronounced, the better.

Even though a patient is legally pronounced as dead at the moment their heart stops, the brain does not begin to deteriorate for some minutes after, therefore giving a window in which to artificially restore blood circulation and preserve brain viability.

As soon as the heart has stopped it is important the body is cooled down to remove the heat. Often ice packs are packed tightly around the body to bring its temperature down.

Brian Wowk, PHD, Technical Consultant to Alcor told gasworld, “Compressed oxygen is used to power heart-lung resuscitators, which are machines that perform CPR on patients for a period of one to two hours.”

“This CPR, or CPS (cardiopulmonary support) as it is referred to in cryonics, uses chest compressions to circulate blood to stabilise the brain and accelerate cooling by facilitating heat exchange with external ice.”

A blood wash-out is then conducted; blood is replaced with an organ preservation solution, and cryoprotectants are infused to protect against freezing injury.

The final step is a controlled cooling to cryogenic temperatures.

Wowk explains, “Gaseous nitrogen at a temperature near -120°C is used to cool patients by external forced convection to temperatures below -100°C over five to eight hours.”

“Patients are then cooled by gaseous nitrogen to near -196°C over two weeks.”

“Final storage is under liquefied nitrogen in vacuum-insulated cryogenic dewars that hold four patients each.”

“The liquid nitrogen maintains a stable temperature of -196°C by slowly and continuously boiling into gaseous nitrogen at a rate of 3 litres a day per patient. It is periodically replenished by a bulk delivery system.”

The Alcor website claims LIN is used because it is inexpensive and reliable.