The Evolution and Efficacy of Medical Masks | PPE Germany
Masks are not a modern invention. They have evolved over a long period of time and have been continuously improved and adapted to areas that people wanted to protect themselves from. These protective measures began as early as the Middle Ages. At that time, they were increasingly made of animal leather and, in addition to coats and gloves, served as protection for doctors treating infectious diseases (e.g. plague). In many cases, these masks were modified to emit smoke to protect against impacting airborne particles known as disease vectors.
In 1897, operations were performed with mouth and nose covers for the first time. This consisted of a layer of gauze bandages and had the advantage that it not only covered the mouth and nose but also the beard (common today as it was then).
At the same time, it could be proven in Breslau that when speaking, droplets with bacteria and pathogens are emitted from the mouth and nose. The contamination area was documented at 4 to 5 meters when speaking.
In 1898, Huebner recommended a mask made of two layers of gauze bandage and showed that it was more efficient. He also criticized the fact that the mask got wet around the mouth and nose and that its retention capacity decreased. Therefore, he developed a frame that ensured the distance to the mouth and nose.
In the years that followed, masks were shown to protect the wearer. In 1918, Weaver reported that diphtheria transmission cannot occur if a mask is worn by persons in contact with diphtheria sufferers. In the same year, military hospitals showed that mask-wearing personnel was better protected against infections than non-mask personnel. It has also been found that normal speech releases the bacteria only 1 to 2 feet (approx. 61 cm), whereas loud or excited speech releases the bacteria up to 3 feet (approx. 91 cm).
Plague outbreaks in what are now parts of China and Russia in 1910-11 killed around 60,000 people then and around 9,300 in 1920-21, with healthcare workers having an astonishingly low rate of infection. This phenomenon can be attributed to the wearing of gauze bandages in front of the mouth and nose, which significantly reduced the absorption of plague pathogens.
In 1918, the Spanish flu hit San Francisco, after which the first general mask requirement was enacted. Unfortunately, since this stopped too early, the second wave hit the city all the harder. For comparison, at a military base in Georgia in the same year, there were only two infected one day, and 716 the next.
By the late 1920s, masks made from gauze bandages were widespread. Engelfried and Farrer showed that a 6-layer mask could reduce bacteria in the surgical field by up to 90%.
A decrease in postoperative wound infections was first recorded in the 1930s. In particular, the decline in streptococci was to be recorded.
New masks, which contained other materials in addition to the gauze, were first tested in the 1930s. Intermediate layers were installed, which consisted of rubber, X-ray films, or cellulose-cotton blends. Later, materials such as cotton, flannel, or paper were also used. Another improvement was the use of an aluminum piece on the nose to seal the mouth-nose region even better and thus guarantee greater protection.
With the introduction of antibiotics in the early 1940s, interest in masks died out. However, Duguid described in 1946 that “on average 39,000 bacterial particles” (meaning droplets) were produced when sneezing: 710 when coughing and 36 when speaking loudly. He also described that particles below 100 µm dry out and shrink to a quarter to a seventh of their original size.
When aseptic techniques became more important in surgery towards the end of the 1950s, masks experienced a resurgence. Preoperative skin disinfection, rubber gloves (introduced by Halsted in 1889), hoods, gowns (introduced by Neuber in 1883) and sterile drapes gained importance in medicine. Various researchers have shown that most particles from the mouth are caught by masks. Filter masks were used for the first time and criticism of the effectiveness of the gauze mask became loud.
Flexible polyvinyl plastic masks were first developed in 1958.
In 1961, the filter mask was used as a disposable product for the first time. It was also pointed out that the masks must be airtight on the cheeks, for example.
In 1960, Rockwood and O'Donoghue defined that:
Masks should be worn by the entire team in the OR
Cover your mouth and nose
A wet mask is to be removed
A new mask is used after each operation
A mask with a filter can be worn for up to 3 hours
Filter based masks are the best
Windows and doors should be closed during the operation
In 1967, researchers studied the retention capacity of various masks (including paper, gauze bandages, nylon, flannel, and polyester) at 15 to 99 percent, depending on the product.
Letts reported in 1983 that only one of 5,595 colonies expelled while talking was Staphylococcus aureus (=spherical, gram-positive bacterium frequently arranged in clusters). The remaining organisms were all commensals, which rarely cause infection. He then advised that there be no conversation in the operating room and that patients wear masks during this time. Shortly after, studies (e.g., by Orrs, Chamberlain, and Houang) found that the mask had no effect on the number of wound infections. However, the number of cases was insufficient. Masks were increasingly used to protect staff from blood spatter beginning in the 1990s.
In the 1990s, there were masks for occupational safety, such as dust masks for construction sites, in addition to masks for medicine. Comparative tests of these particle-filtering masks of type FFP1-3 (filtering facepiece) with surgical mouth and nose protection (MNS) revealed that the FFP masks provided a greater level of protection due to improved cheek and mask sealing. As a result, FFP2 and FFP3 masks were increasingly used in healthcare in the years and decades that followed.
FFP masks are now tested in accordance with the DIN EN 149 standard, while MNS are tested in accordance with the EN 14683 standard. Minimum retention capacity of FFP mask filters (loose fit) in relation to NaCl test aerosol:
FFP1: 80 %
FFP2: 94 %
FFP3: 99 %
Both types of masks protect both the wearer and the wearer. FFP masks can also be equipped with exhalation valves, which make exhalation much easier. These can, of course, only be used if the carrier is not infectious. Experiments with influenza, SARS, and COVID-19 show that the face mask's protective effect is not significantly worse than that of an FFP2 mask. FFP2 masks, on the other hand, are strongly advised when treating patients infected with coronaviruses, avian influenza, or tuberculosis (TB). An FFP3 mask must be worn when dealing with MDR-TBC.
There was a temporary shortage of MNS and FFP masks during the 2009 swine flu pandemic and the 2020 coronavirus pandemic. As a result, some self-made masks, mostly made of textile, were used.
The BfArM referred to these masks as community masks in the context of the corona pandemic:
Community mask (makeshift mouth-nose mask)
Medical face masks (MNS, surgical mask)
Filtering half masks (FFP1-3)
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