Elastomeric Respirator Contamination of Sterile Fields Compared to Surgical Masks (preprint)

Background: Elastomeric half mask respirators (EHMRs) are a reusable, reliable option for protection from infectious aerosol particles such as SARS-CoV2. There is a lack of safety data for their use in sterile fields. We hypothesized an equivalent reduction in aerosol/droplet contamination of the sterile field for an EHMR covered with a surgical mask (EHMRwM) as achieved by a standard surgical mask.Methods: In an operating room setting, participants performed droplet and aerosol generating procedures while wearing: (Group 1) EHMRwM, (Group 2) EHMR only, (Group 3) N95, and (Group 4) surgical mask. A positive control was established with the participant unmasked (Group 5). Contamination of the sterile, anesthesia, and nursing field was measured by microbial growth on settling plates and optical particle counters (0.2+ and 2 um+ particles). 16 experiments were performed by 4 participants with 4 iterations with randomized testing order.Findings: There was a reduction in microbial contamination at the sterile field (p<0.001) for all masks (Groups 1-4) compared to unmasked (Group 5). The mean colony forming units (CFU) at the sterile field was 0 CFUs for EHMRwM, EHMR alone, N95, and surgical mask versus unmasked growing 1·875 CFUs. Compared to the unmasked control, the EHMRwM, EHMR, N95, and surgical masks all resulted in a -0·75 difference in contamination (95% CI -0·91 to -0·48). No significant difference in contamination between the EHMRwM and a surgical mask was detected. No significant difference in particle counts (0·2 µm+ and 2·0 µm+) between the EHMRwM and a standard surgical mask.Interpretation: An EHMR covered by a surgical mask is as effective as a standard surgical mask for reducing contamination at the sterile field in an operating room. Consideration should be given to expanding the use of EHMRs to operating rooms with sterile fields.Funding Statement: No funding sources were used in this research.Declaration of Interests: Brittany E. Howard MD: This author has no personal or financial disclosures. Ryan M. Thorwarth MD: This author has no personal or financial disclosures. Karam Abi Karam BS: This author has no personal or financial disclosures. Sam L. Snider BS: This author has no personal or financial disclosures. Erica Forzani PhD: This author has no personal or financial disclosures related to this research. She does have a pending patent application “SYSTEM AND METHOD FOR MITIGATING AIRBORNE CONTAMINATION IN CONDITIONED INDOOR ENVIRONMENTS” E. Forzani, B. Patel, K. McKay, G. Pyznar, Provisional Patent, August, 2020. Joseph G. Hentz MS: This author has no personal or financial disclosures related to this research. He has previously received grant funding from the Patient-Centered Outcomes Research Institute. Erin H. Graf PhD: This author has no personal or financial disclosures. Bhavesh Patel MD: This author has no personal or financial disclosures. Kelly J. McKay EMT-P: This author has no personal or financial disclosures. Michael L. Hinni MD: This author has no personal or financial disclosures related to this research. He is the inventor of a laryngoscope manufactured and sold by Karl Storz. He receives an honorarium from this. Devyani Lal MD: This author has no personal or financial disclosuresEthics Approval Statement: This study was approved by the Mayo Clinic Institutional Review Board.

Sterile Field Contamination by Elastomeric Respirators Versus Surgical Masks and N95s (preprint)

Background: Elastomeric respirators are reusable and reliable protection from infectious aerosol particles such as SARS-CoV-2. There is a lack of safety data for use in sterile fields limiting application to operating room settings where high-risk aerosol generating procedures are performed. We hypothesized an equivalent reduction in sterile field contamination would be achieved using an elastomeric respirator covered by a surgical mask as compared to a standard surgical mask or N95.Methods: Randomized controlled crossover experiment with repeat measurement comparing microbial and aerosol contamination of operating room surfaces for elastomeric respirators, elastomeric respirators covered by a surgical mask, N95, surgical mask, and no mask. 80 experiments were performed by participants with randomized order and balanced crossover to all masking groups (n=16 per masking group). Participants executed droplet and aerosol generating procedures while wearing: (Group 1) elastomeric respirator with mask, (Group 2) elastomeric respirator only, (Group 3) N95, and (Group 4) surgical mask. Positive control was established with the participant unmasked (Group 5). Contamination was measured by microbial growth on settling plates and optical particle counters (0.2+ and 2 um+ particles).Results: There was a reduction in microbial contamination at the sterile field (p<0.001) for all masks (Groups 1-4) compared to unmasked (Group 5). The mean colony forming units (CFU) at the sterile field was 0 CFUs for elastomeric respirator (+/- mask), N95, and surgical mask versus unmasked growing 1.875 CFUs. Compared to the unmasked control, the elastomeric respirator (+/- mask), N95, and surgical masks all resulted in a -0.75 difference in contamination (95% CI -0.91 to -0.48, p < 0.001). No significant difference in contamination between the elastomeric respirator (+/- mask) and a surgical mask was detected. No significant difference in particle counts (0.2 µm+ and 2.0 µm+) between the elastomeric respirator (+/- mask) and a standard surgical mask.Conclusion and Relevance: Elastomeric respirators with or without mitigation are as effective as a surgical mask and N95 for reducing contamination at the sterile field in an operating room. Consideration should be given to expanding the use of elastomeric respirators to operating rooms during high-risk aerosol generating procedures.