Thursday, January 30, 2020

The Man In The Ironed Mask (Revisited)

Cloth Masks used during the 1918 Pandemic


Earlier today, in  WHO Interim Advice On The Community, Home, Healthcare Use of Masks For nCoV2019swe looked at the inevitable shortage of face masks and N95 respirators during any severe or prolonged epidemic, and the WHO's reluctance to recommend their general use by the public in a community setting.

This, understandably, isn't what most people want to hear, regardless of the limited benefits that wearing masks in public are likely to provide. But even without a negative recommendation, the scarcity of disposable masks during a major outbreak would make it difficult - perhaps even impossible - for much of the public to acquire them.
That said, necessity is the mother of invention.  And if nCoV2019 - or some other respiratory virus - sparks a global epidemic, people are going to try to cobble together some kind of protective gear. 
While their effectiveness is far from assured, over the years we have looked at a few homebrew mask options, which may provide some psychological comfort (and possibly some protection) to those inclined to make them.
These are offered without recommendation (by me, or the WHO), and should be viewed as a `last ditch' line of defense.  Nevertheless, these options have appeared in the CDC's EID Journal, and PloS One, making them at least worthy of some consideration. 
First stop is the 2006 EID Journal Letter, called:
Volume 12, Number 6—June 2006
Simple Respiratory Mask

Virginia M. Dato* , David Hostler*, and Michael E. Hahn*
Author affiliations: *University of Pittsburgh, Pittsburgh, Pennsylvania, USA
To the Editor: The US Department of Labor recommends air-purifying respirators (e.g., N95, N99, or N100) as part of a comprehensive respiratory protection program for workers directly involved with avian influenza–infected birds or patients (1). N95 respirators have 2 advantages over simple cloth or surgical masks; they are > 95% efficient at filtering 0.3-μm particles (smaller than the 5-μm size of large droplets—created during talking, coughing, and sneezing—which usually transmit influenza) and are fit tested to ensure that infectious droplets and particles do not leak around the mask (24). Even if N95 filtration is unnecessary for avian influenza, N95 fit offers advantages over a loose-fitting surgical mask by eliminating leakage around the mask.
The World Health Organization recommends protective equipment including masks (if they not available, a cloth to cover the mouth is recommended) for persons who must handle dead or ill chickens in regions affected by H5N1 (5). Quality commercial masks are not always accessible, but anecdotal evidence has showed that handmade masks of cotton gauze were protective in military barracks and in healthcare workers during the Manchurian epidemic (6,7). A simple, locally made, washable mask may be a solution if commercial masks are not available. We describe the test results of 1 handmade, reusable, cotton mask.

Figure. Prototype mask. A) Side view, B) Face side. This mask consisted of 1 outer layer (≈37 cm × 72 cm) rolled and cut as in panel B with 8 inner layers (< 18 cm2) placed inside (against the face). The nose slit was first placed over the bridge of the nose, and the roll was tied below the back of the neck. The area around the nose was adjusted to eliminate any leakage. If the seal was not tight, it was adjusted by adding extra material under the roll between the cheek and nose or by pushing the rolled fabric above or below the cheekbone. Tie b was tied over the head. A cloth extension was added if tie b was too short. Finally, tie c was tied behind the head. The mask was then fit tested.
For material, we choose heavyweight T-shirts similar to the 2-ply battle dress uniform T-shirts used for protective masks against ricin and saxitoxin in mouse experiments (8). Designs and T-shirts were initially screened with a short version of a qualitative Bitrex fit test (9) (Allegro Industries, Garden Grove, CA, USA). The best were tested by using a standard quantitative fit test, the Portacount Plus Respirator Fit Tester with N95-Companion (TSI, Shoreview, MN, USA) (10). Poor results from the initial quantitative fit testing on early prototypes resulted in the addition of 4 layers of material to the simplest mask design. This mask is referred to as the prototype mask (Figure).
A Hanes Heavyweight 100% preshrunk cotton T-shirt (made in Honduras) ( Link) was boiled for 10 minutes and air-dried to maximize shrinkage and sterilize the material in a manner available in developing countries. A scissor, marker, and ruler were used to cut out 1 outer layer (≈37 × 72 cm) and 8 inner layers (< 18 cm2). The mask was assembled and fitted as shown in the Figure.
A fit factor is the number generated during quantitative fit testing by simulating workplace activities (a series of exercises, each 1 minute in duration). The Portacount Plus Respirator Fit Tester with N95-Companion used for the test is an ambient aerosol instrument that measures aerosol concentration outside and inside the prototype mask. The challenge agent used is the ambient microscopic dust and other aerosols that are present in the air.
A commercially available N95 respirator requires a fit factor of 100 to be considered adequate in the workplace. The prototype mask achieved a fit factor of 67 for 1 author with a Los Alamos National Laboratory (LANL) panel face size of 4, a common size. Although insufficient for the workplace, this mask offered substantial protection from the challenge aerosol and showed good fit with minimal leakage. The other 2 authors with LANL panel face size 10, the largest size, achieved fit factors of 13 and 17 by making the prototype mask inner layers slightly larger (22 cm2).
We do not advocate use of this respirator in place of a properly fitted commercial respirator. Although subjectively we did not find the work of breathing required with the prototype mask to be different from that required with a standard N95 filtering facepiece, persons with respiratory compromise of any type should not use this mask. While testers wore the mask for an hour without difficulty, we cannot comment on its utility during strenuous work or adverse environmental conditions.
We showed that a hand-fashioned mask can provide a good fit and a measurable level of protection from a challenge aerosol. Problems remain. When made by naive users, this mask may be less effective because of variations in material, assembly, facial structure, cultural practices, and handling. No easy, definitive, and affordable test can demonstrate effectiveness before each use. Wearers may find the mask uncomfortable.
We encourage innovation to improve respiratory protection options. Future studies must be conducted to determine levels of protection achieved when naive users, following instructions, produce a similar mask from identical or similar raw materials. Research is needed to determine the minimal level of protection needed when resources are not available for N95 air-purifying respirators since the pandemic threat from H5N1 and other possible influenza strains will exist for the foreseeable future.
Our second stop is a PLoS One article from 2008, which discusses - in more general terms - the feasibility of creating homemade masks useful against respiratory infections for the general public.

Professional and Home-Made Face Masks Reduce Exposure to Respiratory Infections among the General Population
Marianne van der Sande , Peter Teunis, Rob Sabel
Published: July 9, 2008
Governments are preparing for a potential influenza pandemic. Therefore they need data to assess the possible impact of interventions. Face-masks worn by the general population could be an accessible and affordable intervention, if effective when worn under routine circumstances.
We assessed transmission reduction potential provided by personal respirators, surgical masks and home-made masks when worn during a variety of activities by healthy volunteers and a simulated patient.
Principal Findings
All types of masks reduced aerosol exposure, relatively stable over time, unaffected by duration of wear or type of activity, but with a high degree of individual variation. Personal respirators were more efficient than surgical masks, which were more efficient than home-made masks. Regardless of mask type, children were less well protected. Outward protection (mask wearing by a mechanical head) was less effective than inward protection (mask wearing by healthy volunteers).
Any type of general mask use is likely to decrease viral exposure and infection risk on a population level, in spite of imperfect fit and imperfect adherence, personal respirators providing most protection. Masks worn by patients may not offer as great a degree of protection against aerosol transmission.

Arguing against the use of cloth masks - at least by HCWs - is a 2015 study (see BMJ Open: Protectiveness (Or Lack, Thereof) Of Reusable Cloth Medical Masks ) which compared the efficacy of cloth masks to medical masks in a high risk hospital environment.

BMJ Open 2015;5:e006577 doi:10.1136/bmjopen-2014-006577

A cluster randomised trial of cloth masks compared with medical masks in healthcare workers

C Raina MacIntyre1, Holly Seale1, Tham Chi Dung2, Nguyen Tran Hien2, Phan Thi Nga2, Abrar Ahmad Chughtai1, Bayzidur Rahman1, Dominic E Dwyer3, Quanyi Wang4

Published 22 April 2015
Results The rates of all infection outcomes were highest in the cloth mask arm, with the rate of ILI statistically significantly higher in the cloth mask arm (relative risk (RR)=13.00, 95% CI 1.69 to 100.07) compared with the medical mask arm. Cloth masks also had significantly higher rates of ILI compared with the control arm. An analysis by mask use showed ILI (RR=6.64, 95% CI 1.45 to 28.65) and laboratory-confirmed virus (RR=1.72, 95% CI 1.01 to 2.94) were significantly higher in the cloth masks group compared with the medical masks group. Penetration of cloth masks by particles was almost 97% and medical masks 44%.

Conclusions This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally. However, as a precautionary measure, cloth masks should not be recommended for HCWs, particularly in high-risk situations, and guidelines need to be updated.

The recommendation by MacIntyre et al. is that Health care workers not rely on reusable cloth masks, as their use is associated with an increased risk of infection. The authors list a number of limitations to this study, however, and it isn’t at all clear whether wearing cloth masks was detrimental to HCWs. 
They only showed that the lowest rates of infection were in the medical mask group, while the highest rates were seen in those wearing the cloth masks.
And it must be stated that not all cloth masks are created equal (nor are all disposable surgical masks) in terms of quality, fit, and filtration. Additionally, the question as to whether cloth masks have a legitimate role for the public during an epidemic – as a protection of last resort – is not addressed in this study.

And our last stop, in 2014's MERS: Are Two Surgical Masks Better Than One?we looked at a study - published in 2005 in the Journal of Hospital Infection - that looked at the dubious practice of wearing multiple layers of surgical masks in lieu of an N95.

Protecting healthcare staff from severe acute respiratory syndrome: filtration capacity of multiple surgical masks
J.L. Derrick*, C.D. Gomersall
Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China
Summary 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.
The author’s conclude by writing:
In conclusion, our data show that no combination of multiple surgical masks was able to meet the requirements for a respirator. If protection against airborne organisms is required, an N95 respirator or better should be used, as currently recommended by the CDC and WHO guidelines for SARS prevention.
Multiple surgical masks will reduce the number of viruses inhaled, but whether the degree of reduction is sufficient to produce significant protection is unknown and cannot be predicted at present. Multiple surgical masks should, therefore, only be used if N95 masks are not available.
So, the short answer is a double layer of surgical masks does appear to provide more filtration. How much protection that affords in the real world, is another matter. 
If I were out of N95s, and found myself caring for someone who was infected with nCoV2019 or any other novel virus, I’d probably `double up’ with the surgical masks.  I just wouldn’t have a whole lot of faith that I was getting much in the way of protection.
None of these solutions is ideal, and their protective value is debatable.  But there are non-conventional options available, if anyone wants to try them.