Carbon Dioxide in the Medical field

By Sam Rushing, President, Advanced Cryogenics, Ltd.
Special to The Digest

When the average citizen thinks in terms of CO2, from a non- industrial gas perspective, often the thought surrounds concepts covering greenhouse gases, and global warming. On the other hand, in the gas field, thinking in terms of my past tenure with a former CO2 producer, and my consulting work, the primary large volume producers have been food and beverage and frac. On the other hand, this article discusses medical applications for carbon dioxide, which are numerous and ever – growing.

The merchant CO2 industry is enjoying growing usage in biomedical applications. To start, however, there is the long – lived application for CO2 as a respiratory stimulant, and standards relating to a product considered to be critical to public health is expensive to produce, thus representing stronger selling prices. The USP standards are used worldwide in over 130 countries; and this product is often thought of as a medical grade. The merchant producers have select plants to yield this grade of product, usually strategically located; and not huge volume producers, but more expensive premium product to serve this interesting and growing market. The methodology for producing this high grade product is surrounded by expensive quality assurance, assay and production costs. USP has a strong regulatory compliance and audit standard on a plant level; being 99% or greater (v), with high limits on the content of H2O, CO, H2S, NO, NO2, NH3, and SO2. This application is via inhalation, as a respiratory stimulant (also according to the United States Pharmacopeia), with a volume up to 7% with oxygen. USP CO2 is also used to essentially enlarge and stabilize body cavities during a range of surgical procedures; often for less invasive surgical procedures, such as endoscopy.

Cryotherapy, cryosurgery, cryopreservation, are all further applications in the medical field, ranging from cryopreservation (of tissue, cellular material, and gametes); as well as long term preservation of embryos. As for tissue transplant procedures, a hypothermic state may be required, thus less than usual metabolic status. Carbon dioxide has numerous topical applications in cryotherapy and analgesia. A close to physiological atmosphere can be created via blending USP CO2 with medical grade oxygen, in operation of artificial organ systems including kidney dialyzers, and various oxygenators; often including usage in body cavity surgical procedures.

A USP grade CO2 can be used in various freeze drying processes, or lyophilisaton, used in the manufacture of pharmaceuticals; and of course dry ice is often used (generally not USP) for organ and tissue transplant

Some well known applications for USP CO2 include the removal of keratosis and some skin cancers by freezing with liquid CO2 or nitrogen. The same is applicable to the removal or non malignant moles and viral warts. This is a growing demand today, particularly as baby boomers are aging, and seeking skin rejuvenation. CO2 and erbium lasers are used for skin resurfacing; which is a treatment for wrinkles, lines, and sun damaged skin. The theory here is when outer layers of skin are removed, this stimulates collagen production.

In short, medical apps which have direct contact with living tissue and cellular materials require USP, otherwise broadly known as medical grade product. If the product is for freezing or preservation processes which do not touch the tissue directly, then a non- medical CO2 is sufficient.  However, the ever – growing field of biomedical applications includes using the gas for surgical procedures, which can be invasive; or a range of topical approaches for removing unsightly skin and treatment in beauty procedures, which is a significantly growing field. The product is also used in artificial organs and machines which handle body fluids; again, critical to treatment of disease and the medical field.

Any of the sources of CO2 can theoretically source a USP grade product, however, most notably the high content by-product sources such as ammonia, ethanol, and hydrogen/reformer operations often tend to supply these operations. For example, in the United States, Linde has reserved their plants located in Fulton, NY, Lima, OH, and Torrance, CA for USP sourcing.

Outside of the medical grade carbon dioxide, or USP grade in the merchant CO2 trade, with respect to strict grade definition and standards, would be the ISBT grade, or beverage grade product. These two grades tend to be the primary grades, with strict standards and test methodology requirements. When speaking of ‘food grade’ this can be associated with CGA grades, or sometimes defined by what the processor specifies within their organization alone. Therefore, food grade is not as controlled as USP or ISBT grades. Next, when thinking of industrial grades, remember many plants produce a ISBT grade to serve all needs. Some do not serve the beverage markets, thus less testing, and strict quality standards are not followed as diligently for overall service from food to metallurgical apps. Some plants may be reserved specifically for frac and industrial service, thus incapable of food and beverage; where often such plants are surrounded by the oil and gas market. These examples do not consider a USP product, however.

Therefore, applications drive the quality and grade of CO2. However, USP is a strictly defined product for medical apps, and ISBT is a beverage grade product; and the later often serves all markets (assuming a non – USP requirement exists), thus making for an easier operational standard. The applications for medical service are quite interesting and impressive; and will continue to grow.

About the author:

Sam A. Rushing is president of Advanced Cryogenics, Ltd., with a strong consulting and merchant background. Mr. Rushing is a chemist, who is called upon for CO2 and cryogenic gas consulting tasks ranging from technical, process, purity; to market, business development and expert witness work. Phone 305 852 2597, e-mail: rushing@terranova.net; web: www.carbondioxideconsultants.com