The 3M™ Bair Hugger™ warming system’s technology has been used in more than 170 studies and more than 60 randomized controlled clinical trials. Its ability to maintain normal body temperature can provide a range of benefits, from lower mortality rates to shorter hospital stays. 

Plaintiff lawyers suing 3M and the Bair Hugger warming system cite several studies in their lawsuits. These studies suggest that, in theory, the heat generated by the Bair Hugger system could affect air flow in the operating room.

It’s important to know that the majority of these studies were associated with Scott Augustine and his company, Augustine Biomedical + Design, a competitor in the patient-warming space. Mark Albrecht, one of the researchers on six of the eight studies, worked for Augustine at the time. 

Plaintiff lawyers also do not mention some crucial facts:  None of the studies directly link surgical site infections to the Bair Hugger system; none of them show that the Bair Hugger system has ever caused a surgical site infection. 

A respected independent research group, ECRI, examined the scientific literature and determined that the evidence does not justify discontinuing the use of Bair Hugger warming technology. ECRI also chastised Augustine Temperature Management for mischaracterizing the results of the review.  The report is here. 

Here are the studies cited by plaintiff lawyers, with the passages they don’t discuss:  

Because of the nature of our experiment we are unable to conclude that the use of the forced air warming device….would actually lead to an increased risk of surgical site infection.
— Legg et al. Do forced air patient-warming devices disrupt unidirectional downward airflow? J Bone and Joint Surg-Br. 2012;94-B:254-6
Our findings do not establish a direct link between forced air warming and increased surgical site infection rates. . .
— Albrecht M, Leaper D et al. Forced-air warming blowers: An evaluation of filtration adequacy and airborne contamination emissions in the operating room. Am J Infect Control 2011;39:321-8
Thus, we are unsure of the exact degree of ventilation disruption that might occur in a working OR during orthopedic surgery…future research is warranted to characterize the clinical conditions under which forced air warming excess heat results in ventilation disruption during surgery.
— Belani et al. Patient warming excess heat: The effects on orthopedic operating room ventilation performance. Anesthesia & Analgesia 2012 (prepublication on-line) 2013;117(2):406-411
This study does not show that forced-air warming increases the risk of infection. . .
— Legg A, et al. Forced-air patient warming blankets disrupt unidirectional airflow. Bone Joint J. 2013 Mar;95- B(3):407-10 (Ex. V)
Another limitation of the study is that the definitive effects of this excess heat on clinical outcomes is presently unknown.
— Dasari et al. Effect of forced air warming on the performance of operating theatre laminar flow ventilation. Anaesthesia 2012;67:244-249
[T]he present study did not evaluate the link between forced air warming and surgical site infection rates. . .
— Leaper D et al. Forced-air warming: a source of airborne contamination in the operating room? Orthopedic Rev. 2009;1(2):e28
This study does not establish a causal basis for this association [the patient warming device and the risks of surgical site infections in the study.]
— McGovern et al. Forced-air warming and ultra-clean ventilation do not mix. J Bone and Joint Surg-Br. 2011;93(11):1537-1544
Last, we did not track hospital infections, nor did we study the association between FAW [forced- air warming] contamination generation/emission and hospital infection rates. . .
— Reed M, et al. Forced-air warming design: evaluation of intake filtration, internal microbial buildup, and airborne- contamination emissions. AANA J. 2013 Aug;81(4):275-80 (Ex. W)