Watch the Video about Laminar Flow Disruption by Forced-air Warming
Please watch the video. It is honest, unaltered footage taken in a simulated OR of laminar flow ventilation being disrupted by forced-air warming. What you will see is physics at work.
The physics is simple: heat rises! After passing over the patient’s skin and dropping near the dirty floor, the waste hot air rises--overpowering the ultra- clean downward air current of laminar flow-- and then, having cooled, falls into the surgical site.
Reducing surgical site infections (SSIs) is of the highest priority for hospitals, insurance companies, and national health initiatives. Not to mention patients and their families.
Providing an ultra clean surgical environment with laminar flow has become the standard of care because it helps reduce hospital acquired infections. A study cited by the Centers for Disease Control revealed a reduction in SSIs from 3.4% to 1.6% merely as a result of laminar flow.
Warming surgical patients, of course, is also the standard of care. Normothermic patients are far less likely to acquire a post-operative wound infection—64% less likely by one study (Mahoney, AANA J, 1999)—than those who aren’t warmed. The device used to warm patients, however, should not increase the risk of bacterial contamination.
Fortunately, there is an [air-free] alternative. HotDog® conductive fabric warms as effectively as forced air, but is safe, eco-friendly, and much less expensive.
We encourage you to conduct the simple test detailed at the end of the video to prove that the forced-air exhaust heat rises in your operating room. Of course, it will. Hot air always rises.
We want to hear your comments about hot air and its effects on laminar flow. Your thoughts and knowledge are important to us.
It is not possible to compare the thousands of cubicmeters of air circulated by the laminar air flow system to the few hundred liters of air from the warmair blower.
ReplyDeleteThe effect of the forced air warming on the laminar air flow is less than opening a door into the operating room or like a person moving around close to the laminar air field.
gibler, thank you for your comment and your interest in the topic. You are correct that the protection of laminar flow is fragile and there are other factors such as people in the flow that are capable of disrupting it. However, research shows that the main reason that forced air warming (FAW) disrupts laminar flow is the waste heat and this disruption is relatively independent of the volume of the waste air. Physics dictates that heated air will always rise. Because the waste air from FAW is warm with 800-1000 watts of waste heat, it rises along the sides of the operating table and easily penetrates the downward traveling laminar flow air, despite the difference in air volume. If the rising warm air is contaminated with bacteria from the blower, the patient or from air resident near the floor, it is obvious that this contaminated air should never end up in the sterile field. However, research shows that in the presence of FAW, the contaminated air from the floor clearly ends up in the sterile field above the wound in relatively high concentrations.
ReplyDeleteResearch also shows that a person standing beside the operating table within the laminar air flow has about the same impact on particle counts in the sterile field that FAW alone has. However, the presence of both FAW and a person beside the table further increases particulate counts over the wound by a factor of 10! The person disrupts the laminar flow allowing the warm air to rise into the sterile field even more efficiently.
To answer your comment, forced-air warming clearly causes contamination of the sterile field over the wound with particles originating near the floor, despite the “protection” of laminar air flow. The contamination of the sterile field by FAW is even more severe in the presence of other laminar flow disrupting variables such as a surgeon standing by the table. There are more studies forthcoming.
Thank you for posting.
Nice post.
ReplyDeleteVery useful informative blog.
Thanks for great sharing.
jessimen
If all the above is true then why isn't everyone using Ready-Heat, Heated Disposable Medical Blankets. Military medicine has been using them for over 5 years without an issue. The blanket moves from pre-op to post op without a single plug and play or blower device. Infection control is not an issue and the blankets made from medical nonwovens is 100% disposable and at a fraction of the cost
ReplyDeleteTed – although it is true that Ready-Heat blankets don’t blow hot air – which we’ve shown is indeed a good thing – and the blankets have some advantages for military or emergency medical transport, they are not suitable for intraoperative use. There is no research showing effectiveness, the design does not cater to surgical patients, and there are no built-in safety mechanisms to ensure temperature accuracy. The Ready-Heat product has no chance in the operating room.
ReplyDeleteI am interested in contact information for you and the Northumbria researchers who produced the fantastic videos. Here at my company we also believe there is a broad perception that mitigating sources of airborne infection in the OR involves simply installing a laminar flow regime without regard to the extreme dynamics of surgery.
ReplyDeleteThank you,
Sean Self, self@nimbicsystems.com