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Smoke Evacuation Systems

The most effective way to protect personnel and patients from inhaling the harmful constituents of surgical smoke and aerosol is to use a mechanical smoke evacuator system with a high-efficiency filter during all smoke-generating procedures.

Mon Aug 01 2011By Lanier Norville, TechNation Magazine

The most effective way to protect personnel and patients from inhaling the harmful constituents of surgical smoke and aerosol is to use a mechanical smoke evacuator system with a high-efficiency filter during all smoke-generating procedures. The effectiveness of smoke evacuation was demonstrated conclusively in Wenig’s study of the effects of electrocautery and Nd:YAG laser plume on rat lungs. In that study, compared to rats exposed to smoke without evacuation, the lungs of rats exposed to exhaust from a single-filter smoke evacuator had milder degrees of pathologic changes.

 A smoke evacuator is basically a vacuum pump with one or more filters designed to evacuate surgical smoke and aerosol from the operative site, filter out essentially all of the contaminants and return the filtered air to the OR.

The main components of a hospital-grade smoke evacuation system are:

  • A filter system, which traps harmful matter and permits the return of filtered air to the operating room 
  • A vacuum source that pulls the air into the nozzle, through the tubing, and through the filter
  • Disposable hose and accessories that connect the unit to the surgical site
  • An electronic control panel that controls unit operations, eliminates interference with other devices and facilitates maintenance functions
  •  An activation device.

Filter System

The smoke evacuator’s filter system removes particles from the suctioned airstream at the surgical site. There are three general types of filters: activated carbon, membrane, and depth media filters.

The activated carbon filter provides odor control and absorbs gases.

 A membrane filter efficiently captures particles larger than its pore size (e.g., a 0.5-µm filter will block a 10-µm particle). Membrane filters are thin, highly efficient, and have well defined filtration characteristics. They generally have higher flow resistance and a lower particle-loading capacity (the number of particles per unit of area that can be captured before the filter’s performance is affected) than depth-media filters.

 A depth media filter consists of randomly oriented glass or polypropylene fibers. The open spaces between the densely packed fibers are much larger than the particles to be captured, so filtering action depends on the particles coming in contact with and adhering to the fibers, through the forces of inertial impaction, electrostatic attraction, and diffusion. Because of their much lower flow resistance, higher particle capture capacity, and longer life, most smoke evacuators use depth-media filters.

The different types of filters that may be found in hospital-grade smoke evacuators are as follows:

  •  Prefilter: Prefilters made of sponge or wire grating are used to capture objects (e.g., cotton), fluid, or gross particulates that can be accidentally sucked into the airstream and subsequently damage the high-efficiency filter or the evacuator pump.
  •  HEPA filter: A High Efficiency Particulate Air (HEPA) filter captures 99.97% of DOP particles 0.3

            µm in diameter. Three particles out of 10,000 pass through the filter.

  •  ULPA filter: An Ultra Low Penetration Air (ULPA) filter is designed to capture very small particles and organisms. It captures 99.999% of DOP particles 0.12 µm in diameter. One particle out of 100,000 passes through. Research has shown that pathogens such as HIV, HPV, and HBV particles are found attached to droplet nuclei, and that the total size of the particle is significantly larger than the 0.1-µm particles that an ULPA filter is designed to capture.  

Some evacuators have a single, self-contained multi-stage, integrated filtering system, in which different levels of contamination and microorganisms are removed as the smoke is channeled through the filter. Such filters are easy to remove and replace. Multi-piece filtering systems, which may include a single-use prefilter, are more costly and cumbersome to use, but may extend the life of the ULPA filter.

 

Read more in the August issue of TechNation Magazine.

 

View the Smoke Evacuation System category on MedWrench.

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