Análise da integridade e funcionalidade das máscaras N95/PFF2 em protocolos de reuso e uso estendido e a segurança dos profissionais de saúde

Abstract

Introduction: In the context of the global shortage of N95/PFF2 respirators during the COVID-19 pandemic, protocols for extended use and reuse were adopted despite the lack of scientific evidence regarding their impact. Objective: To determine the effectiveness of N95/PFF2 respirators in terms of integrity and functionality, considering sealing and filtration performance after extended use and reuse, with a focus on the occupational safety of healthcare professionals. Method: Experimental research conducted in the Bioengineering Laboratory of the Universidade Federal de Minas Gerais and in the Advanced Microscopy and Mechanical Testing Laboratories of the Pontifícia Universidade Católica de Minas Gerais, with support from the Bioengineering Centre. N95/PFF2 respirators used by nursing professionals in Intensive Care Units of one public and one private hospital were analysed. Data collection occurred in three phases: structured questionnaire; retrieval of the devices; and assessments including visual inspection, scanning electron microscopy, tensile testing and filtration efficiency testing using a dedicated experimental prototype. Descriptive statistics, Chi-square, Fisher’s Exact test, Student’s t-test and ANOVA were applied, with α = 0.05 and a 95% confidence interval. Results: A total of 265 nursing professionals participated. Most did not feel safe with the protocol, highlighting moisture, dirt and storage conditions as major concerns. Filtration efficiency was mentioned once in both protocols, while training appeared only in the fifteen-day protocol. Training on respirator use was received by 53.6% (seven days) and 74.1% (fifteen days), mainly in 2020, with emphasis on donning and doffing. Seal checking and visual inspection were performed by 20.9% and 46.4% (seven days) and by 26.8% and 35.7% (fifteen days). In the seven-day protocol, training was associated with seal checking (p = 0.002). There was no exclusive location for storing respirators. After seven days, visual inspection revealed folds (5.7%), identification marks (17.1%), internal dirt (31.4%), strap loosening (34.3%) and external dirt (60%). After fifteen days, tears (2.9%), identification marks (28.6%), folds (37.1%), external dirt (54.3%) and internal dirt and strap loosening (100%) were identified. Fold, internal dirt, tears and strap loosening were more frequent after fifteen days (p < 0.001). Scanning electron microscopy revealed increased pore size, fibre loosening, micro-holes and debris from seven days onwards, intensifying at fifteen days. In tensile testing, unused straps showed greater elasticity, strength and time to rupture; after seven and fifteen days, there was progressive reduction in these properties (p < 0.001). Regarding filtration efficiency, both protocols presented mean values < 94% (91.5% and 91.9%), with similar proportions of respirators below this threshold (45.7% versus 51.4%; p = 0.632), indicating equivalence. Conclusion: Reuse compromised structural integrity, fibre morphology, strap strength and elasticity, as well as reducing filtration efficiency. Perceived safety was low and training for safe reuse was insufficient, reinforcing the need to reassess reuse protocols to ensure the occupational safety of healthcare professionals.