Postoperative wound infections and surgical face masks: a controlled study. Use of face masks by non-scrubbed operating room staff: a randomized controlled trial. Protecting healthcare staff from severe acute respiratory syndrome: filtration capacity of multiple surgical masks.
It has never been shown that wearing surgical face masks decreases postoperative wound infections. On the contrary, a 50% decrease has been reported after omitting face masks. The present study was designed to reveal any 30% or greater difference in general surgery wound infection rates by using face masks or not. During 115 weeks, a total of 3,088 patients were included in the study. Weeks were denoted as "masked" or "unmasked" according to a random list. After 1,537 operations performed with face masks, 73 (4.7%) wound infections were recorded and, after 1,551 operations performed without face masks, 55 (3.5%) infections occurred. This difference was not statistically significant (p greater than 0.05) and the bacterial species cultured from the wound infections did not differ in any way, which would have supported the fact tha the numerical difference was a statistically "missed" difference. These results indicated that the use of face masks might be reconsidered. Masks may be used to protect the operating team from drops of infected blood and from airborne infections, but have not been proven to protect the patient operated by a healthy operating team. Ambiguity remains about the effectiveness of wearing surgical face masks. The purpose of this study was to assess the impact on surgical site infections (SSIs) when non-scrubbed operating room staff did not wear surgical face masks.
                Eight hundred twenty-seven participants undergoing elective or emergency obstetric, gynecological, general, orthopaedic, breast or urological surgery in an Australian tertiary hospital were enrolled. Complete follow-up data were available for 811 patients (98.1%). Operating room lists were randomly allocated to a 'Mask group' (all non-scrubbed staff wore a mask) or 'No Mask group' (none of the non-scrubbed staff wore masks). The primary end point, SSI was identified using in-patient surveillance; post discharge follow-up and chart reviews. The patient was followed for up to six weeks.
                Overall, 83 (10.2%) surgical site infections were recorded; 46/401 (11.5%) in the Masked group and 37/410 (9.0%) in the No Mask group; odds ratio (OR) 0.77 (95% confidence interval (CI) 0.49 to 1.21), p = 0.151. Independent risk factors for surgical site infection included: any pre-operative stay (adjusted odds ratio [aOR], 0.43 (95% CI, 0.20; 0.95), high BMI aOR, 0.38 (95% CI, 0.17; 0.87), and any previous surgical site infection aOR, 0.40 (95% CI, 0.17; 0.89).
                Surgical site infection rates did not increase when non-scrubbed operating room personnel did not wear a face mask. Guidelines issued by the Centers for Disease Control and Prevention and the World Health Organisation state that healthcare workers should wear N95 masks or higher-level protection during all contact with suspected severe acute respiratory syndrome (SARS). In areas where N95 masks are not available, multiple layers of surgical masks have been tried to prevent transmission of SARS. The in vivo filtration capacity of a single surgical mask is known to be poor. However, the filtration capacity of a combination of masks is unknown. This was a crossover trial of one, two, three and five surgical masks in six volunteers to determine the in vivo filtration efficiency of wearing more than one surgical mask. We used a Portacount to measure the difference in ambient particle counts inside and outside the masks. The best combination of five surgical masks scored a fit factor of 13.7, which is well below the minimum level of 100 required for a half face respirator. Multiple surgical masks filter ambient particles poorly. They should not be used as a substitute for N95 masks unless there is no alternative.
From the limited results it is unclear whether the wearing of surgical face masks by members of the surgical team has any impact on surgical wound infection rates for patients undergoing clean surgery.