Interventional Cryotherapy Platform Harnesses Liquid Nitrogen

A new minimally invasive spray cryotherapy system treats the entire spectrum of esophageal disease, from Barrett's Esophagus (BE) to cancer.

The CSA Medical (Lexington, MA, USA) truFreeze cryotherapy system uses an extremely cold liquid nitrogen spray to flash-freeze and destroy unwanted tissue in patients suffering from BE, esophageal cancer, and airway obstructions. The system also enables tissue rejuvenation from underlying healthy tissue, in contrast to the scar tissue that forms after heat-based modalities such as radio-frequency ablation (RFA). Using the extreme cold of liquid nitrogen (-196°C) also helps circumvent potential problems resulting from other cryogens such as nitrous oxide (-88°C), which cannot get the tissue cold enough or act fast enough to penetrate and ablate cancer cells.

The truFreeze System offers two venting options: active venting, in which an onboard suction is used to evacuate gas from the ablation area via a cryodecompression tube (CDT), which is used when spraying distal to an obstruction or flaccid organ that could potentially collapse; and passive venting, in which gas disperses from the ablation area by natural diffusion, without suction. The diameter of the area through which gas vents passively must be adequate to ensure distention does not occur. Passive venting may be used with a vent tube when spraying proximal to a resistor where the lumen is open.

“I recommend spray cryotherapy ablation to many of my esophageal cancer patients because it penetrates deeper than other ablation therapies, without the scarring and post-procedural pain associated with radiofrequency burning or balloon ablation,” said Professor Vanessa Shami, MD, of the University of Virginia Medical Center (Charlottesville, USA). “The ability to perform the procedure as an outpatient therapy that allows patients to go home the same day provides significant quality of life benefits to a population that may be suffering from a range of health challenges.”

Liquid nitrogen is a colorless cryogenic fluid which boils at -196 °C (at sea-level atmospheric pressure), causing rapid freezing on contact with living tissue. As the liquid-to-gas expansion ratio of nitrogen is 1:694, it boils to fill a volume with nitrogen gas very quickly. It is therefore stored in special insulated containers called Dewar flasks that are vented to prevent pressure buildup. Depending on the design, it can be stored for hours or for up to a few weeks.

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