Study finds air purifiers don't reduce surgical infection risk

Daniel Sessler, MD, professor and vice president for clinical and outcomes research at McGovern Medical School at UTHealth Houston. (Photo by UTHealth Houston)

A study of more than 110,000 surgeries found that adding advanced air purification and sterilization systems to operating rooms did not reduce surgical site infections, postoperative complications, or deaths. Suggesting that hospitals should instead focus on preventing direct contamination of surgical wounds. 

The study was published in the journal Anesthesiology. 

Surgical site infections remain a leading cause of postoperative illness, death, and hospital readmissions according to the Centers for Disease Control and Prevention. These infections develop in the skin, tissue, organs, or implanted material involved in a surgical procedure. About 1% to 3% of patients recovering from surgery develop a surgical site infection, although the risk is significantly higher for some procedures such as colorectal surgery. 

“The causes of surgical site infections are not well understood,” said Daniel Sessler, MD, professor and vice president for clinical and outcomes research at McGovern Medical School at UTHealth Houston. “We know the bacteria that cause them, but we do not know where the bacteria come from and why patients develop infections. There are many potential sources, and bacteria floating through the operating room is among them.” 

To test the theory that airborne bacteria contribute to surgical site infections and that filtering the air reduces risk, they installed two air-purification systems in each of 68 operating rooms for four weeks at a time over the course of several years. Thirty-four operating rooms received an active air-purification system that filtered air and eliminated bacteria and other contaminants, while the remaining rooms received identical inactive units that looked and sounded the same. After four weeks, the systems were switched. Neither patients nor the clinical teams knew which operating rooms contained the active systems. 

At the conclusion of the study, researchers found no difference in infection-related complications between periods with active and inactive air-purification systems. The findings suggest airborne bacteria may not be a major source of surgical site infections in modern operating rooms. 

“This tells us we should shift our focus elsewhere,” Sessler said. “We are one step closer to identifying the factors that contribute most to these infections. Hospitals may benefit more from focusing on other possible sources, including bacteria from a patient’s own skin, bacteria from the intestines, or infection prevention after surgery.” 

Sessler said future research should evaluate air-purification systems in less sterile environments, such as hospital wards and intensive care units. He said the greatest opportunity to reduce infections may come from limiting direct wound contamination and improving surgical practices rather than adding additional air-cleaning technology. 

Other authors include Alparslan Turan, MD, professor of anesthesiology, critical care, and pain medicine at McGovern Medical School; Edward J. Mascha, PhD; Elyad Ekrami, MD; Mauro Bravo, MD; Catalina Dussan, MD; Federico Almonacid-Cardenas, MD; and Yanyan Han, MS, of Cleveland Clinic in Ohio and the Outcomes Research Consortium in Houston, as well as the ORACLE trial investigators.