自 COVID-19 疫情爆发以来，变化最大的活动之一就是工作。实施居家隔离令后，美国大部分地区被迫待在室内，导致许多人失业或在家办公。几个月后，企业重新开业并实施政策和程序，以防止 COVID-19 在员工和客户之间传播。CDC 建议使用呼吸防护和面罩作为感染控制设备。有几种类型的呼吸防护/面罩可供选择，效果各不相同。

医用口罩：已获 FDA 批准；可防护大滴飞沫

外科口罩的使用可以追溯到 20 世纪初，当时它们由多层纱布制成，医院的外科手术团队佩戴它们来防止开放性伤口受到污染。现代外科口罩在疾病预防方面的效果各不相同。标准外科口罩已获得 FDA 批准。外科口罩不能保护佩戴者避免吸入小颗粒。外科口罩可以防止大液滴、飞溅物和身体或其他危险液体。这种口罩可以有效地保护患者免受医疗服务提供者的呼吸排放。外科口罩不能提供紧密的面部密封，导致用户吸入时泄漏。在医疗环境中使用时，应在每位患者使用后将其丢弃。

呼吸器：从危害到医疗保健

The first respirators were also created in the early 1900’s, to protect those in hazardous positions, like miners, firefighters and soldiers. Healthcare providers began using them in the 1990’s. Today, there is the standard N95 respirator and the surgical N95 respirator. Both can be used as protection from small aerosol particles, as well as large droplets. Surgical N95 respirators are reserved for healthcare providers, in that they provide protection against airborne particles and hazardous fluids. When mandatory for the performance of an individual’s job, these devices must be fit tested to ensure a tight-fitting seal against the face. Some N95 masks are equipped with exhalation valves which makes breathing easier. These are not recommended for sterile environments, however.

Respirator effectiveness is measured by the percentage of particles being filtered, the amount of oil resistance and the APF (Assigned Protection Factor). For example, an N95 mask collects at least 95% of particles. The letter refers to the amount of resistance to oil aerosols, which reduces the filter’s effectiveness. An “N” type respirator offers no oil resistance; a respirator with the letter “R” is somewhat resistant to oils, and may be used for 8 hours in an industrial setting; “P” means the mask is strongly resistant to oils and has no time limits. An APF is the workplace level of respiratory protection that a respirator or class of respirators is expected to provide to employees…” (OSHA.gov, “Assigned Protection Factors for the Revised Respiratory Protection Standard,” February 2009) For example, N95 respirators have an APF of 10, which means only 1/10 of aerosols/particles in the air will be inhaled by the wearer. Respirators should be discarded after each patient, and when they become soiled, damaged or difficult to breathe in. NIOSH (National Institute of Occupational Safety and Health), an agency within the CDC, grants approvals for respirators.

NIOSH-approved Respirator Lists:

• https://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/
• https://www.cdc.gov/niosh/npptl/topics/respirators/cel/

Elastomeric Respirators: Best Kept Secret

A third type of protection is the Elastomeric respirator, which is a NIOSH-approved, reusable device utilizing N95 filter cartridges. This respirator is constructed of synthetic or natural rubber material. Because the Elastomeric respirator is reusable, less money is spent over time, when compared to the costs associated with disposable respirators. It is roughly 10 times less expensive than N95 respirators. The Elastomeric is also a viable substitute when disposable masks are in low supply. It is easily disinfected with a bleach and water solution and has an APF of 10. A supply of replaceable parts must be stocked, such as inhalation/exhalation valves (and valve covers), filters, cartridges, canisters and straps. The Elastomeric is available in half or full facepiece versions. Full facepiece respirators cover the eyes, which is very important in preventing the spread of illness.

Elastomeric respirators with exhalation valves are not suitable for surgical environments. Any of the three filter types may be used with this device: N, R or P. A fit test must be passed when first adopted and every year thereafter. In a study at Allegheny Health Network, close to 2,000 healthcare workers were given Elastomeric respirators for one month. The results were very favorable. Users felt the mask was comfortable, and patients did not have adverse reactions. All workers chose to continue using the Elastomeric respirators, instead of returning to N95 respirators.

Powered Air Purified Respirators (PAPR): Highly Effective and Flexible

The Powered Air Purified Respirator (PAPR) is a battery-operated system which removes aerosols and droplets (as well as gases and vapors) from the air through filters, cartridges and canisters. There are three versions: full facepiece; loose-fitting hood/helmet; tight-fitting half-mask. The full facepiece has an APF of 1,000 and requires fit testing; tight-fitting units require fit testing and have an APF of 50; loose-fitting devices do not require fit testing and have an APF of 25. These devices are very effective, allowing only a minute percentage of airborne contaminates to reach the user. However, some of the drawbacks include the loud blower, limited field of vision, and higher initial costs.

Face Shields: From the Hospital to the Classroom

Face shields are made from rigid, clear plastic and cover the entire face, from the top of the forehead to beneath the chin. They protect the wearer from sprays of hazardous substances, such as coughs, sneezes or vomit. In some healthcare environments, face shields are worn along with N95 respirators. Face shields are wonderful options for teachers because students having the ability to see facial expression is a major key to learning.

Cloth Face Coverings: Wear These to Protect Others

Finally, there are the cloth facemasks, which became popular when the volume of available N95 respirators was limited. Many retailers are selling cloth masks with a plethora of stylish designs, making them appealing to large numbers of consumers. The jury is still out on their effectiveness, however. The CDC does not recommend cloth masks for children under 2 years old, or anyone who has trouble breathing, is unable to remove mask without assistance, or is unconscious or incapacitated. The CDC recommends that individuals wear cloth masks to prevent spreading the virus to others. The mask should cover the nose and mouth and fit snugly against the sides of the face. Cloth masks should be washed after each use.

There are many options for respiratory protection and face coverings, depending on the environment. It is important to keep in mind that a face covering, regardless of its effectiveness, is only one element of a prevention plan. The CDC maintains that people should continue practicing preventative habits, even while wearing a face covering, such as social distancing, regular hand washing (or using hand sanitizer when soap is not available), and avoiding sick people. As the economy struggles to re-open, it is crucial that everyone do their part in preventing the spread of this illness. A collective effort is required to see a substantial reduction in the number of COVID-19 cases.

References

“Use of elastomeric respirators could reduce providers’ need for N95 masks,” McKnight’s Long-Term Care News, June 15, 2020. [Online]. Available: https://www.mcknights.com/news/clinical-news/use-of-elastomeric-respirators-could-reduce-providers-need-for-n95-masks/

“Understanding respiratory protection options in Healthcare: The Overlooked Elastomeric,” NIOSH Science Blog, CDC, July 6, 2017. [Online]. Available: https://blogs.cdc.gov/niosh-science-blog/2017/07/06/elastomerics/

“Elastomeric Respirators: Strategies During Conventional and Surge Demand Situations,” Coronavirus Disease 2019 (COVID-19), CDC, April 20, 2020. [Online]. Available: https://www.cdc.gov/coronavirus/2019-ncov/hcp/elastomeric-respirators-strategy/

“Considerations for Optimizing the Supply of Powered Air-Purifying Respirators (PAPRs),” Coronavirus Disease 2019 (COVID-19), CDC, April 19, 2020. [Online]. Available: https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/powered-air-purifying-respirators-strategy.html

“Personal Protective Equipment: Questions and Answers,” CDC, March 14, 2020. [Online]. Available: https://www.cdc.gov/coronavirus/2019-ncov/hcp/respirator-use-faq.html

“How to Wear Cloth Face Coverings,” Coronavirus Disease 2019 (COVID-19), CDC, March 22, 2020. [Online]. Available: https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-to-wear-cloth-face-coverings.html

信息图：“了解差异”（医用口罩/N95 口罩），CDC，[在线]。网址：  https ://www.cdc.gov/niosh/npptl/pdfs/UnderstandDifferenceInfographic-508.pdf

“修订后的呼吸防护标准的指定防护因素”，美国职业安全与健康管理局，2009 年。[在线]。网址：  https://www.osha.gov/Publications/3352-APF-respirators.pdf

L. Brousseau 等人，《N95 呼吸器和外科口罩》，NIOSH 科学博客，CDC，2009 年 10 月 4 日。[在线]。网址：  https: //blogs.cdc.gov/niosh-science-blog/2009/10/14/n95/