Video Evidence of the Vortex Caused by the Radiant Waste Heat from FAW Blankets

The video clip below is an excerpt from a nurse education course.  It shows the vortex-effect caused by the radiant waste heat from forced-air patient warming (FAW) blankets, similar to what was recently studied and published by orthopedic surgeons A.J. Legg and A.J.Hamer.

The Legg and Hamer study, published in the Bone & Joint Journal in March 2013, is different than the four previous studies examining the unintended consequence of FAW.  Studies by Belani, Dasari, McGovern and a previous study by Legg all showed the mass effect of waste heat forming thermals under the drapes and rising from the floor to the surgical field.  The latest study is unique because it shows that the radiant heat travels through the drapes, interacts with the downward flow of air from the ceiling ventilation, and forms vortices that suck contaminated air from the floor.  Legg and Hamer discovered 2,000x more contaminant particles at the surgical site when FAW was used than when air-free HotDog patient warming was used.

This is especially concerning in orthopedic surgery, where airborne contaminants can cause devastating deep-joint infections.

As you’re watching the short video clip, notice the tight-spinning vortex captured by orthopedic surgeons in Northumbria, UK, towards the end.

Study: Contamination Increased 2000x With Bair Hugger Warming

Minneapolis, MN: March 14, 2013— The use of Bair Hugger forced-air warmers during surgery creates convection currents that capture particles below the surgical table, lifting them into the sterile surgical field, according to research recently published by orthopedic surgeons. The waste heat radiating through the surgical drape induced the formation of tornado-like vortexes of rapidly spinning air near the surgical site. The vortexes sucked contaminated air from the operating room floor and deposited it over the surgical wound. 

2,000 times more contaminant particles were found in the air over the wound with Bair Hugger warming than with air-free HotDog conductive warming. With HotDog patient warming, only 1,000 particles per cubic meter of air were present. With Bair Hugger warming, the particle count was 2,174,000 per cubic meter, an increase of 217,300% 

Concerned by convection currents produced by hot-air warming devices, orthopedic surgeons A.J. Legg and A.J. Hamer from Northern General Hospital in Sheffield, United Kingdom, compared the torso-style disposable blankets of 3M’s Bair Hugger system with the reusable, air-free HotDog conductive warming system. The surgeons released particles below the surgical table and then measured how many were transported to the surgical site. Neither surgeon has any financial relationship with either of the products studied. 

The study was published in the February issue of The Bone and Joint Journal and entitled “Forced-air patient warming blankets disrupt unidirectional airflow.” 

Dr. Scott Augustine, inventor of both products studied, stated, “Such a massive increase in airborne contamination is obviously a safety issue in contamination-sensitive surgeries. In joint replacement surgery, for example, a single airborne bacterium can cause a deep joint infection.” 

Periprosethetic joint infections are often catastrophic: immense pain and suffering, permanent disability and an enormous cost to the hospital. 

“Every joint infection is a disaster—both for the patient and the system,” said Dr. Augustine. “The process is horrific: ex-plant the joint, prolonged hospitalization, 6-8 weeks of IV antibiotics and then—assuming no amputation—re-implant the joint. The average cost is around $100,000.” More than 12,000 of these infections occur each year in the US, a rate that some see as a significant public health problem.

Evidence of the risks of forced-air warming just keeps growing.

A study published online ahead of print in Anesthesia & Analgesia concludes that forced-air patient warming produces waste heat that disrupts operating room ventilation airflows over the surgical site, transporting non-sterile air to the area and hindering the ventilation system’s ability to clear potential airborne contaminants.

“There are some in our industry that would like you to believe that hot air doesn’t rise,” says Dr. Scott Augustine, “this study proves, once again, that that argument is insulting to science and common sense.”

Belani, et al, focused on contamination-sensitive surgery at the University of Minnesota, using a mannequin draped for total knee replacement.  Introducing neutral buoyancy bubbles near the mannequin’s head, researchers found a significant increase in bubble-count over the surgical site when forced air warming was used, as opposed to conductive fabric or the control.  The study states: