To the Editor—The indication of unidirectional airflow (UAF) with an airflow velocity between 0.25 and 0.45 m s−1 in the operating room to reduce surgical site infections (SSIs) is actually questionable, according to the recent international publications.Reference Pinder, Bottle, Aylin and Loeffler1–Reference Singh, Reddy and Shrivastava3 The WHO 2016Reference Allegranzi, Zayed and Bischoff4 and CDC 2017Reference Berríos-Torres, Umscheid and Bratzler5 guidelines no longer advocate the use of an UAF as a preventive measure to reduce the risk of SSI. However, some authors still recommend doing so in prosthetic orthopedic surgery.Reference Jutte, Traversari and Walenkamp6 The question of the choice of the type of airflow and the air control performance arises or will arise in hospitals during the renovation or the construction of a new operating room.
Recent International Literature
In the study published by Barbadoro et alReference Barbadoro, Bruschi and Martini7 in 2016, 2 periods were compared: 2001–2013 with turbulent flow use and 2004–2013 with UAF use.Reference Barbadoro, Bruschi and Martini7 After multivariate analysis, a significant decrease of SSI incidence in an operating room equipped of UAF was observed in clean + clean-contaminated surgeries (odds ratio [OR], 0.57; 95% confidence interval [CI], 0.48–0.68) and in contaminated + dirty surgeries (OR, 0.31; 95% CI, 0.17–0.56), respectively. However, this study suffers from numerous biases (ie, nonrandomized single-center survey, no control group, and “before and after” study design).
The meta-analysis published by Bischoff et alReference Bischoff, Kubilay, Allegranzi, Egger and Gastmeier2 in 2017 compared the efficiency of UAF versus turbulent flow in different surgeries. Overall, 12 studies were selected including observational studies (n = 9) or registered database analysis (n = 3). The meta-analysis of 8 cohorts showed no difference in deep SSI incidence after 330,146 hip replacement procedures (OR, 1.29; 95% CI, 0.98–1.71; P = .07; I² = 83%). Furthermore, no difference was detected after 134,368 knee arthroplasties (meta-analysis of 6 cohort studies; OR, 1.08; 95% CI, 0.77–1.52; P = .65; I² =71%). There was no significant difference between digestive and vascular surgeries. The findings of this study are under debate.Reference Jutte, Traversari and Walenkamp6
In 2017, Oguz et alReference Oguz, Diab-Elschahawi and Berger8 published a single-center randomized study assessing the influence of 4 factors on the bacterial air contamination after orthopedic surgery: (1) use of UAF, (2) duration of surgical procedure, (3) presence of professionals in the operating room and (4) type of warming (ie, pulsed-air or non–pulsed-air heating system). The patients were randomized into 2 groups, according to the type of warming: pulsating air or electric heating. The unidirectional versus nonunidirectional flow comparison was performed within each randomized group. In multivariate analysis, a significant increase of the number of bacteria in the air was detected according to the duration of the intervention in the absence of UAF.
Recent International Guidelines
In 2016, the WHO published recommendations for SSI preventionReference Allegranzi, Zayed and Bischoff4 and concluded: “laminar flow ventilation should not be used in patients receiving arthroplasty.” The quality of the recommendation was “conditional” and the level of evidence “low to low enough.” In 2017, the Centers for Disease Control and Prevention (CDC)Reference Berríos-Torres, Umscheid and Bratzler5 and the American College of Surgeons and Surgical Infection SocietyReference Ban, Minei and Laronga9 published respectively new guidelines for SSI prevention without a specific recommendation on that topic (ie, “no recommendation” or “unresolved issue”).
Discussion
Since the publication by Lidwell et alReference Lidwell, Elson and Lowbury10 in 1987, no new randomized clinical trial was published on this topic until the latest randomized study assessing the air quality in the operating room published by Oguz et alReference Oguz, Diab-Elschahawi and Berger8 in 2017. However, the endpoint was microbiological, and patients were not randomized according to the type of flow. Bischoff et al’s meta-analysisReference Bischoff, Kubilay, Allegranzi, Egger and Gastmeier2 or the recent World Health Organization (WHO) guidelinesReference Allegranzi, Zayed and Bischoff4 synthesized disparate and heterogeneous studies but relied on solid methods (grading of recommendations, assessment, development and evaluations, GRADE). However, the GRADE method is not always suitable and was not performed in 2015 to grade the French recommendations. With the current state of knowledge, the French Society of Hospital Hygiene highlights the importance of initiating a global risk analysis beyond on the air performance class in the operating room. The new French guidelines oublished in 2018 recommend the possible use of UAF only in prosthetic orthopedic surgery to reduce aerobiocontamination (with no SSI reduction evidence) and with a low level of recommendation. But this measure needs to be included in a bundle of prevention measures, including personal behavior and antibiotic prophylaxis, which remains the major preventive factor. This French opinion and new recommendations aim to help international hospitals in their choice of appropriated airflow, especially when designing or renovating an operating room.
Author ORCIDs
Didier Lepelletier, 0000-0001-9054-907X
