Surgical Smoke Evacuation Technology Has Come of Age: CFM vs. Capture Velocity

The harmful effects of surgical smoke (plume) on patients, surgeons, nurses and OR staff is well documented and has become a matter of growing concern within the healthcare community. Fortunately, advances in surgical smoke evacuation technology have brought about significant progress in reducing the dangers of exposure to surgical plume.

It’s not about air flow: Thirty-five years ago surgical smoke was siphoned from ORs with an apparatus that functioned like a vacuum cleaner. A wand held near the surgical site would draw air from the room into a length of tubing and then into a receptacle. The amount of air that flowed through the tubing, measured in cubic feet per minute (CFM), was considered to be the measure of effectiveness of the evacuation process.

These primitive smoke removal systems were inefficient in both design and functionality. Powered by crude, noisy turbine-driven pumps, the suction machines produced heat, noxious odors and continuous noise in the OR. The systems were not auto-regulated, and so created a level of turbulence, din and disruption such that many surgeons chose to not use them at all. Above all, the devices were largely ineffective in removing harmful plume from ORs because a large percentage of the smoke escaped into the room despite the fact that air was flowing copiously through the tubing mechanism.

In the late 1980s, a breakthrough came with the realization that the capture velocity (i.e., the amount of suction) at the smoke evacuation wand nozzle is the true measure of evacuation effectiveness, not the amount of air flowing through the tubing. Researchers demonstrated that when enough suction is present at the device nozzle to cause high airflow and pressure, a vortex is created around the ESU blade, making the CFM measurement in the tubing irrelevant.

It’s the Venturi principle: Today’s advanced surgical smoke evacuation devices employ a design that pulls air through a narrow opening at very high speeds causing the air to spin and form a powerful air vortex around the ESU blade. When air travels through this narrow opening at very high speed, air pressure is created inside the opening. In order for the air to fit inside the opening, it must spin in a vortex. This is known as the Venturi principle.

Smoke particles expelled from the surgical site are captured in the air barrier created by the vortex before they escape. Thus, instead of trying to catch and pull back particles that are traveling away from the smoke nozzle, smoke evacuation devices such as I.C. Medical’s Crystal Vision create an invisible barrier that encloses the surgical site in an upside-down tornado and through which smoke particles cannot escape into the OR.

When smoke particles expelled from the surgical site in any direction encounter the air barrier created by the vortex, they are drawn into the air vortex and trapped. In other words, the device traps smoke and captures the harmful particles contained in that smoke before it escapes into the air instead of suctioning it after it is released through tubing.

In addition to being a more efficient, effective and reliable method of smoke evacuation, this technology allows for smoke evacuation equipment design to be smaller, quieter, easier to handle, and enables accurate manipulation during surgical procedures. Indeed, since being introduced into the market by I.C. Medical 27 years ago, this technology has been adopted and accepted as worldwide industry standard.

Importantly, as a result of this technology, airflow is now essentially an irrelevant efficiency measure because it is the amount of suction and not the amount of air flowing through the tubing that determines system effectiveness.

The importance of capture velocity is identified on the Center for Disease Control and Prevention (CDC) website in DHHS (NIOSH) Publication No. 96-128 in a section entitled Ventilation, which states: “The smoke evacuator should have high efficiency in airborne particle reduction and should be used in accordance with the manufacturer’s recommendations to achieve maximum efficiency. A capture velocity of about 100 to 150 feet per minute at the inlet nozzle is generally recommended.” http://www.cdc.gov/niosh/docs/hazardcontrol/hc11.html

Experts agree that evacuation of surgical smoke near its source is the best way to prevent plume exposure and the health consequences associated with it. When evaluating smoke evacuators, there is no question that suction capacity is the crucial factor to be considered — with CFM to be considered secondarily if at all.

 

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