Operation Room Air Flow Study with 3M™ Bair Hugger™ Warming System in Simulated Hip Replacement Surgery
John P. Abraham, Ph. D., University of St. Thomas and Jennifer A. Wagner, Ph. D., Prism Environmental Health and Safety Solutions
The Bair Hugger Warming System provides a safe and effective way to maintain normal body temperature during surgery. When used properly the Bair Hugger Warming System lowers the risk of hypothermia and improves patient recovery and surgery outcomes (i.e. reduces risk of surgical site infection, blood loss and transfusion requirement, prolonged recovery, and fatal heart attack). A scientific research project was undertaken to assess whether the Bair Hugger System disturbed the clean-air flow in an operating room in the vicinity of a sterile surgical site. The investigation showed that the Bair Hugger Warming System did not disrupt the normal airflow patterns of an operating room, and did not move air from the floor to the surgical site in a simulated hip replacement procedure.
The investigation had three separate components. One part of the investigation incorporated advanced mathematical calculations based upon the fundamental laws of physics to track the paths of airflow in the operating room. The calculations demonstrated that the air from the Bair Hugger System avoided the surgical site. The air flow that emerged from the Bair Hugger System traveled away from the surgical table and migrated toward the room exhaust vents along with the air beneath the operating table– not toward the surgical site.
A second part of the investigation involved experiments performed in an operating room with flow visualization studies that purposely injected visible fog into multiple locations in the room: 1) behind the anesthesia screen where the Bair Hugger air would exit near the patient’s head; 2) underneath the surgical table; and 3) next to the surgical table, near the surgical team, and near the surgical site. This investigation found that downward clean moving air from ceiling supply ducts in an operating room inhibited air from other sources from intruding into the surgical region. The downward flow of clean air worked irrespective of whether the Bair Hugger Warming System was used or not.
The third part of the investigation included a review of the scientific literature. The best scientific work did not show any causal link between the use of a Bair Hugger Warming System and surgical site infections. Even contrary research, which was largely funded by a competitive company, failed to show any causal link. More than 170 clinical studies have utilized the Bair Hugger system, and studies have demonstrated forced-air warming’s clinical effectiveness. Studies have demonstrated perioperative temperature management with forced-air warming actually reduces the risk of surgical site infections1, surgical bleeding3-5 and risk of heart attack6.
The findings of the three components of this investigation mutually reinforce one another. All of these studies showed that the Bair Hugger Warming System is safe when used according to manufacturer directions, providing an effective way to maintain patient temperature.
Sponsored by 3M Health Care, Infection Prevention Division
1. Kurz, A. Sessler, DI. Lenhardt, R. Perioperative Normothermia to Reduce the Incidence of Surgical Wound Infection and Shorten Hospitalization. N Engl J Med. 1996;334:1209-15.
2. Mahoney, CB. Odom, J. Maintaining intraoperative normothermia: A meta-analysis of outcomes with costs. AANA Journal. 1999;67(2):155-164.
3. Rajagopalan, S. Mascha, E. Na, J. et. al. The Effects of Mild Perioperative Hypothermia on Blood Loss and Transfusion Requirement. Anesthesiology. Jan 2008;108(1):71-77.
4. Schmeid H, Kurz A, Sessler DI, Kozek S, Reiter A. Mild hypothermia increases blood loss and transfusion requirements during total hip arthroplasty. Lancet 1996:347(8997):289–92.
5. Winkler M, Akça O, Birkenberg B, et al. Aggressive warming reduces blood loss during hip arthroplasty. Anesth Analg 2000;91(4):978–84.
6. Frank SM, Fleisher LA, Breslow MJ, et al. Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events: a randomized clinical trial. JAMA 1997;277:1127–34.