Protecting staff against airborne viral particles: in vivo efficiency of laser masks

doi:10.1016/j.jhin.2006.06.021

Journal of Hospital Infection

Volume 64, Issue 3, November 2006, Pages 278-281

https://doi.org/10.1016/j.jhin.2006.06.021 Get rights and content

Summary

Laser masks are used to prevent inhalation of viral particles during laser surgery. A crossover trial was performed in eight volunteers to compare the ability of a surgical mask and a laser mask with that of an FFP2 respirator to filter airborne dust particles. The surgical and laser masks were tested when worn normally and when they were taped to the face. The mean reductions in particle counts were 3.0 fold [95% confidence interval (95% CI) 1.8–4.2] for the untaped surgical mask, 3.8 fold (95% CI 2.9–4.6) for the untaped laser mask, 7.5 fold (95% CI 6.5–8.5) for the taped surgical mask, 15.6 fold (95% CI 13.5–17.8) for the taped laser mask, and 102.6 fold (95% CI 41.2–164.1) for the FFP2 half-face respirator. The laser mask provided significantly less protection than the FFP2 respirator (P = 0.02), and only marginally more protection than the surgical mask. The continued use of laser masks for respiratory protection is questionable. Taping masks to the face only provided a small improvement in protection.

Introduction

Viable viral particles have been shown to be aerosolized by diathermy, laser and a variety of surgical instruments.1, 2, 3, 4 Laser masks, sometimes called ‘submicron masks’, have been used to protect staff from these potentially infectious airborne viral particles.² These masks are similar to surgical masks in design but have an improved filtering material.

Surgical masks perform poorly in in vivo tests of filtration, and it has been suggested that this is due to leakage around the sides of the mask, both inwards and outwards.5, 6, 7, 8 Although laser masks have an improved in vitro filtering capacity compared with surgical masks, they may also perform poorly in vivo as they have a similar design to surgical masks. To date, no reports on the efficacy of laser masks in vivo have been published.

The aim of this study was to examine the in vivo ability of laser masks to reduce the ambient concentration of submicron-sized particles, and then to compare a laser mask with a surgical mask and an FFP2 respirator, the latter being a standard respiratory protective device used to protect staff against airborne pathogens. To determine whether leakage from the face seal contributed towards poor performance of the surgical mask, both the surgical and laser masks were tested when worn normally, and when the mask was taped to the face to eliminate leakage.

Section snippets

Methods

This was a prospective unblinded study in healthy volunteers who had previously passed a quantitative fit test on the 1862 FFP2 respirator (3M, St Paul, Minnesota, USA). Each subject was tested on three different protective devices: a standard surgical mask (Surgikos, Johnson & Johnson, Arlington, TX, USA), a laser plume mask (Barrier, Mölnlycke Health Care, Newtown, PA, USA) and a fitted FFP2 filtering facepiece respirator (1862, 3M, St Paul, Minnesota, USA). The Surgikos mask is a pleated

Results

Filtration efficiencies of the devices are shown in Figure 2. The mean reductions in particle counts were 3.0 fold [95% confidence interval (CI) 1.8–4.2] for the untaped surgical mask, 3.8 fold (95% CI 2.9–4.6) for the untaped laser mask, 7.5 fold (95% CI 6.5–8.5) for the taped surgical mask, 15.6 fold (95% CI 13.5–17.8) for the taped laser mask, and 102.6 fold (95% CI 41.2–164.1) for the FFP2 half-face respirator. Statistical comparison between the following five groups was made: surgical mask

Discussion

Although the laser mask was capable of filtering much smaller particles than the surgical mask in vitro, the difference between the two masks was found to be small in vivo. The FFP2 mask is designed to have a tight seal, and the mean particle count reduction using this mask was 102 fold, compared with a 3.8-fold reduction using the laser mask and a 3.0-fold reduction using the surgical mask. These data indicate that, in vivo, the laser mask more closely approximated the performance of the

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Citation Excerpt :
Wearing conventional surgical masks reduces on average the outward particle emission rates while speaking and coughing by 90% and 74%, respectively [102]. However, the pore size of conventional medical masks’ filter material is usually too large to trap small viral particles effectively [103]. FFP2, FFP3, and N95 face masks provide better protection against airborne pathogens [103].
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To determine the effect of taping the top of face masks on air particle counts directed toward the eye during simulated intravitreal injections.
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Thirteen healthy subjects were recruited. Each wore a cloth, surgical, or N95 mask in randomized order. The number of air particles were quantified by using a particle counter suspended over the right eye while each subject breathed normally, deeply, or spoke using a standardized script. Particle counts were obtained with the top of each mask taped and not taped. The main outcome measurements were particle counts of 0.3, 0.5, 1, 3, 5, and 10 μm and total particle counts.
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Understanding routes of transmission of SARS-CoV-2 is a key element in establishing both occupational health and public health guidelines in the Covid-19 management. SARS-CoV-2 is found in patients’ airways, including for asymptomatic ones. Available data suggest a underestimated risk of air transmission of SARS-CoV-2 when an infected individual coughs or sneezes, but also when he speaks or simply breezes, the majority of emitted particles being smaller than 1 μm. Preliminary data indicate the presence of viral RNA in air samples and on surfaces far from source patients. However, it is important to note that the detection of viral genetic material by RT-PCR does not mean that the virus is alive or infectious. According to data on the quantification of the infective power of such aerosol with small size particles and if such air transmission was confirmed, a larger use of N95 respirators should be promoted particularly in health care units.
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^☆: Presented in part as a free paper on 14 November 2004 at the Hong Kong College of Anaesthesiologists' Annual Scientific Meeting, Hong Kong.

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Protecting staff against airborne viral particles: in vivo efficiency of laser masks☆

Summary

Introduction

Section snippets

Methods

Results

Discussion

Ophthalmology

J Oral Maxillofac Sur

J Hosp Infect

Am J Surg

Viral disease transmitted by laser-generated plume (aerosol)

Arch Dermatol

Laryngeal papillomatosis with human papillomavirus DNA contracted by a laser surgeon

Eur Arch Otorhinolaryngol

Blood-containing aerosols generated by surgical techniques

Am Ind Hyg Assoc J