This column is about real critical cleaning cleaning (flushing) of human wound cavities of air with gaseous CO₂. These cavities are naturally full of air during cardiopulmonary bypass operations with an empty heart, and other open wounds.

CO₂ IN CLEANING OPERATIONS
Cleaning operations including cleaning of rust from metal, particles from semiconductors, and operations of intermediate value have long been done with CO₂. The phase of the CO₂ has been solid, liquid, gas, or fluid.

CO₂ as a solid cleaning agent has taken the form of a cryogenically-produced pellet sized similar to a BB or a snowflake produced by expansion of pressurized liquid. Though not commercially successful, use of liquid CO₂ has been patented for dry cleaning as a replacement for perchloroethylene. And the U.S. Department of Energy has patented use of supercritical CO₂ (SCCOR), with selected co-solvents for use in removing intractable materials such as photoresists by causing them to swell with dissolved CO₂.

CO₂ vs. AIR
The chief problem with the presence of air in contact with human tissue during surgical operations has been that air is soluble in human tissue. Divers know this. They are concerned about increased solution of air in blood and tissue at higher pressures under water, and then release of that air when the pressure lessens as the diver returns to the surface. This leads to formation of small air bubbles (chiefly Nitrogen) in the blood which act as blockages (embolic) in arteries.

If air was more soluble in human tissue, this would be less of a problem because the air would remain dissolved in the diver's tissue. CO₂ is that more soluble gas.

It is more soluble in human tissue — 25 times more soluble. Known from the 1950s, arterial CO₂ emboli are much better tolerated than air emboli. In addition, CO₂ is 50% heavier than air (44/28), which facilitates displacement of air in a wound cavity.