Common Question: “My OR doesn’t use laminar flow. Does waste hot air still matter?”

Answer: Absolutely. Consider the following:

What is laminar ventilation and what is conventional ventilation?

Operating room air is typically introduced from the ceiling, moves towards the floor, and exits through the side vents. US standards for hospital construction require that operating room ventilation be filtered, at a minimum, to an efficiency of >90% for the removal of germ sized particles. Many ventilation systems do much better than that, by employing High Efficiency Particulate Air filtration commonly known as HEPA, which by definition removes >99.97% of germ sized particles from the airflow.

Conventional Ventilation Laminar Ventilation (Ultra-clean)
Air filtration less than HEPA Air filtration is HEPA (99.97%)
Downward air current is non-uniform Uniform, high-velocity air current
Multiple ceiling vents, angles, and velocities Uniformity minimizes turbulence
Creates significant turbulence in the ventilation air Unless disrupted, eliminates contaminant mobilization into the sterile field


Why does our research focus on laminar flow ventilation?

It’s difficult to visually show the effects of waste heat with either tracer particles or neutral buoyancy bubbles in conventional ventilation operating rooms because the turbulent air-currents disrupt the visual patterns.

What types of procedures are most impacted by rising hot air?

Whether a surgery is performed under laminar flow ventilation or conventional ventilation, it only takes one germ to infect a wound when prosthetic devices are implanted. Therefore, avoiding contaminating the sterile field with rising hot air is most important in orthopedic, cardiac, or other implant surgeries. Blowing contaminated air into the surgical site should not be tolerated during such procedures.

Does waste heat matter during general surgery with conventional ventilation?

Yes. Although the risks and consequences are much greater in ultra-clean implant surgery, you still don’t want germs blowing around the surgical site under any circumstances. A recent study in the American Journal of Infection Control titled “Forced-air warming blowers: An evaluation of filtration adequacy and airborne contamination emission in the operating room,” found:
• 58% of blowers were generating significant levels of particles downstream of the intake filter. The authors theorized that this may be related to the release of built- up contaminants acquired during previous periods of use.
• 92% of FAW blowers showed viable microorganism growth from air path swabs, including MRSA.

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