Carbon Dioxide Adsorbents for Medical Applications

There are many serious conditions that can develop as a result of ineffective carbon dioxide removal, especially in clinical settings. Recent innovations in high-tech materials have a better safety record and a better ability to prevent adverse reactions than conventional formulations. Read about notable innovative materials in this Frost & Sullivan analysis.

Carbon dioxide (chemical formula CO2) is famous for being that poisonous gas that we exhale.  It is the end product of cellular reproduction in all aerobes: organisms that use oxygen for metabolism. The CO2 that is generated in the tissues is dissolved in the blood and is transported to the lungs via the venous network. The lungs then expel the gas—an act that we recognize as respiration. Ineffective expulsion of CO2 leads to a condition known as hypercapnia or hypercarbia—or, simply, CO2 retention. Hypercapnia is most commonly caused by lung diseases and hypoventilation or respiratory depression. Hypoventilation, in turn, can be caused by chronic mountain sickness, damage to the brain stem or adverse drug reactions that increase the concentration of CO2 in the bloodstream, leading to acidosis.

The importance of CO2 removal becomes even more pronounced in clinical settings, where patients who are on ventilator support or are administered anesthesia may require assistance to effectively eliminate the gas from the body. In such closed-circle respiratory systems, CO2 elimination occurs through the process of adsorption, which refers to surface-level adhesion of gases, atoms or molecules to an activated surface. Adsorption differs from absorption, which is the phenomenon of one fluid getting dissolved in another. Medical-grade CO2 adsorbents need to meet additional safety and efficacy criteria so that they do not dry out during critical clinical and surgical applications. Recent innovations in high-tech materials have resulted in adsorbents with a better safety record and a better ability to prevent adverse reactions than conventional soda lime-based formulations. A brief profile of notable innovative materials is presented here.

Amsorb Plus by Armstrong Medical Ltd. (Coleraine, Northern Ireland)

Amsorb Plus caters mainly to anesthesia care: low-flow anesthesia is complicated by issues such as poor adsorbent capability and toxicity. Armstrong Medical eliminated the use of soda lime and sodium hydroxide and instead based the adsorbent scaffold on calcium chloride, which is a biocompatible humectant. Calcium chloride is chemically inert and does not react with commonly used anesthetic drugs such as sevoflurane, enflurane, isoflurane and desflurane. A particularly useful feature of this material is that once the adsorption capacity has been exhausted, the material changes color—an indication for the hospital staff to change it.

LoFloSorb by Intersurgical Ltd. (Berkshire, United Kingdom)

Most conventional adsorbents contain standard 3% sodium hydroxide. When they become dry, they begin to extrude compounds that can react with some of the volatile compounds in anesthesia. Hence, the dryness threshold has to be increased to an extent that it becomes inert. Intersurgical has achieved this by creating a chemical mix that eliminates the use of alkali hydroxides. Its flagship product, LoFloSorb, instead uses 92.5% calcium hydroxide and 7.5% silica. The adsorbent matrix is in the form of particles a few millimeters in diameter. The material serves the European respiration and anesthesia markets, but the company plans to expand into non-healthcare markets including deep-sea diving and mining—both being exercises that run the risk of hypercapnia. 

EcoSorb by Vetland Medical (Louisville, Ky.)

EcoSorb is also calcium hydroxide-based; the innovativeness lies in its particle design. EcoSorb consists of D-shaped microparticles that provide better packing density as a scaffold. The particle shape also ensures that the surface area available for CO2 adsorption is maximized. EcoSorb has high adsorption capacity during low-flow anesthesia, with 150 liters of CO2 per kilogram of adsorbent. The material also has a moisture content of 15.5% in order to prevent the particles from drying out during usage in closed-circle respiration and veterinary applications—a niche market in which Vetland Medical is a leader.

Yabashi Lime by Yabashi Holdings (Ogaki, Japan)

The Japanese brand Yabashi Lime makes a strong case for the sustained relevance of soda lime in the carbon capture market, even in the face of new materials. The company has enhanced the soda lime formulation by retaining 16% moisture by weight. The material also eliminates the presence of strong alkalis that could chemically interact with drugs or induce the production of carbon monoxide—another gas that can result in respiratory toxicity. The particles are designed in a kind of clover shape in order to maximize the surface available for adsorption.

The Road Ahead

The clinical requirement for anesthesia is not going to diminish in the years to come. On the contrary, with the number of invasive procedures increasing, the importance of carbon capture during the procedure will also increase. A key research focus for this technology is to increase adsorption capacity without the utilization of strong alkali components. 

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