Prediction of N95 Respirator Fit from Fogging of Eyeglasses: A Pilot Study

Abstract

A bstract Aim and objective Fogging of eyeglasses while wearing N95 respirators is common. It is commonly held that the N95 respirator has a poor fit if there is fogging of eyeglasses. We conducted this prospective, pilot study to determine if fogging of eyeglasses predicts poor fit of N95 respirator. Materials and methods Seventy volunteer healthcare workers from a tertiary intensive care unit in Sydney, Australia participated. The participants donned one of the following N95 respirators: three-panel flat-fold respirator (3M 1870), cup-shaped respirator (3M 1860), or a duckbill respirator. After a satisfactory “user seal check” as recommended by the manufacturer, the participants donned eyeglasses and checked for fogging. A quantitative fit test (QnFT) of the respirator was then performed (using PortaCount Respirator Fit Tester 8048, TSI Inc., Minnesota, USA). A fit factor of <100 on quantitative fit testing indicates poor fit. The sensitivity and specificity for fogging of eyeglasses (index test) to predict the poor fit of N95 respirator was determined, compared to QnFT (gold standard test). Results Fogging of eyeglasses as a predictor of poor respirator fit (i.e., fit factor <100 on QnFT) had sensitivity of 71% (95% CI, 54–85%) and specificity 46% (95% CI, 29–63%). The odds ratio of fogging as a predictor for poor fit was 2.10 (95% CI, 0.78–5.67), with a two-tailed p -value of 0.22 (not significant). The receiver operating characteristic curve for fogging of eyeglasses as a diagnostic test had the area under the curve of 0.59. Conclusion Fogging of eyeglasses is neither a sensitive nor a specific predictor for poor fit of N95 respirators. How to cite this article Kyaw S, Johns M, Lim R, Stewart WC, Rojas N, Thambiraj SR, et al. Prediction of N95 Respirator Fit from Fogging of Eyeglasses: A Pilot Study. Indian J Crit Care Med 2021;25(9):976–980.

Health effects of filtering facepiece respirators: Research and clinical implications of comfort, thermal, skin, psychologic, and workplace effects

“…The investigators speculate that these measured effects correlate with ocular symptoms of dryness in those wearing FFRs 81 . Fogging of protective eyewear was found to occur frequently 78,79 …”

“…81 Fogging of protective eyewear was found to occur frequently. 78,79 Two studies use standard measures of cognitive function in controlled laboratory experiments. Neither found significant effects upon cognitive function.…”

“…Since leakage of warm air contributes to fogging of eyewear, 78 improperly fitted and worn FFRs often impair vision. 79 An incorrectly large size, failure to mold the respirator over the bridge of the nose, or upward slipping may all interfere with vision. Alterations in the lower visual fields might also occur.…”

A systematic review of passing fit testing of the masks and respirators used during the COVID-19 pandemic: Part 1-quantitative fit test procedures

“…Subjects of 60 studies were HCWs, the professional group’ HCWs were included the following: four studies: anaesthetists and predominantly anaesthetic technicians, anaesthetic consultants and trainees [ 5 , 35 , 63 , 64 ], five studies: physicians [ 65 – 69 ], one study: respiratory therapist [ 66 ], twenty-one: nurses [ 37 , 40 , 41 , 59 , 66 , 67 , 69 – 83 ], one study: administration [ 84 ], four studies: allied health staff [ 40 , 59 , 80 , 84 ], seven studies: medical or clinical staff [ 59 , 73 , 80 , 82 , 84 – 86 ], one study: paramedic staff [ 78 ], three studies: medical practitioner [ 40 , 80 , 83 ], one study: aged care or disability worker [ 40 ], two studies: medical imaging staff [ 40 , 80 ], five studies: other healthcare worker [ 40 , 59 , 78 – 80 ], five studies: non-clinical role [ 40 , 80 , 81 , 83 , 86 ], one study: infection control practitioners [ 87 ], two studies: laboratory workers [ 45 , 88 ], eight studies: doctors [ 41 , …”

“…A total of eight studies assessed the influence of respirator style on respirator fitting [ 33 , 70 , 80 , 82 , 95 , 107 , 128 , 130 ]. In four studies, cup-shaped respirators had the highest passing fit rate [ 33 , 70 , 80 , 130 ].…”