April 7, 2020
Background: As COVID-19 cases become more frequent across the country, healthcare workers are becoming increasingly infected. In order to continually provide care to our unique set of patients, it is important that efforts are taken to not only care for our patients, but also protect our colleagues and ourselves (and families). COVID-19 is spread through person to person transmission, predominantly the virus being secreted through the airway of the infected (although coronavirus has been isolated from feces and urine). In order to prevent disease acquisition, respiratory droplet barriers combined with minimization of virus entering the airway through a person’s hand carrying virus to mucosal surfaces have proven effective. During the SARS epidemic (also a coronavirus), much was learned about barrier and hygiene protection.
The basis for this summary is the experience of existing practices (CDC guidelines and others), literature review of prevention of SARS infection of healthcare workers and Cochrane review (2011, “Physical Interventions to Reduce the Spread of Respiratory Viruses”). As multiple areas of potential contamination exist with potential for various infectious inocula, the COVID-19 Strike Force attempts to “risk stratify” exposures by likelihood of exposure. It is now thought that up to 25% of people with COVID-19 infection may be asymptomatic, making community acquisition a real possibility, especially for those around children. RNA viral infections in immunosuppressed transplant recipients often have high viral loads (super shedders) suggesting that when the transplant provider is in contact with COVID-19 infected organ recipients, it would be prudent to take self-protection seriously. The risk mitigation for the health care provider centers on the reduction of viral entry into the airway through social distancing and isolation of the infected person to reduce inoculum exposure. For those who must be in close contact with infected people, frequent hand washing/hygiene and airway and physical barriers (masks and skin protection) are the underpinnings of risk mitigation of contracting COVID-19.
Respiratory droplet: The best way to stop the spread of respiratory infections is for uninfected people not to inhale or self-inoculate themselves with virions. This is the basis for self-isolation and social distancing of > 6 feet between people. This is also the most effective method to stop community person to person spread. Use of homemade masks appear to be effective in reducing the distance that droplets travel and are now accepted by the CDC as a means to decrease community transmission. Routine surgical masks will reduce the amount and distance travelled by droplets expelled from a person with respiratory illness and limit somewhat the numbers of virions entering the wearer’s airway. Masks on coughing or suspected COVID-19 people being evaluated should be routine. Health care workers caring for the ill should use available barriers proportional to the extent and degree of their exposure to infectious inocula. The infectious inoculum must reach the cells where the virus can replicate to cause disease (respiratory epithelium and alveolar cells with ACE2). Without any barrier, large droplet (>10 micron) mostly become stopped in the upper airway, while aerosols (<10 microns) can reach the alveoli. The closer one is to the source of an expelled inoculum, the greater the number of virions that enter the airway. The goal is either to eliminate or reduce the inoculum size to a subinfectious dose.
Airway Barriers in the Healthcare setting
Surgical Masks: There is evidence to suggest that the simple barrier of a surgical mask will reduce the infectious droplet inocula 4 fold (van der Sande, 2008) and is non-inferior to N95 masks in the prevention of influenza acquisition in an outpatient setting (Radonovich,2019). The non-inferiority may be related to the “loss of N95 fit” over the prolonged outpatient shifts, rather than an actual equivalence of the two types of masks. This recognition forms the recommendation that in a high prevalence area (such as a hospital with COVID-19 patients) or in public with high densities of people in midst of infectious outbreak, that healthcare providers wear surgical masks.
N95 Masks These devices prevent the passage of 95% of particles smaller than 0.3 microns. An important factor in their effectiveness is “fit testing” to reduce leakage of air exchange around the sides of the mask. When used properly, these masks are highly effective in the reduction of droplets that carry COVID-19 into the wearer’s airway. However, over time and with repetitive activity (such as with children) the seal and effectiveness decreases. There is literature that N95 is no more effective than routine surgical masks in an outpatient setting where use compliance was not routine. Healthcare workers should wear fitted N95 masks while working directly with COVID-19+ patients, standards for products from other countries/jurisdictions can be found at: https://multimedia.3m.com/mws/media/1791500O/comparison-ffp2-kn95-n95-filtering-facepiece-respirator-classes-tb.pdf . Previous recommendations for the use of a single mask per day has had to be modified with PPE shortages. It is recommended that N95 masks be discarded when the integrity is compromised or there is loss of seal. Re-use of N95 masks is often a necessity.
Hazmat suits: the ultimate respiratory protection can have a hermetically sealed self-contained respiratory system. They are impractical for routine healthcare as currently designed.
The premise behind barrier protections is to minimize the amount of virus that is transmitted to the individual’s respiratory system after touching a surface and then transferring the virus to the mouth and nose (entry to airway). Frequent hand washing with soap is the time proven technique to reduce transmission of respiratory viruses. However there are a variety of situations where an extraordinary exposure to droplets and secretions occur and precautions need to be taken when one is confronted with high levels of bodily secretions containing infectious particles (areas with intubations, Emergency department, ventilators, suctioning, and close contact of COVID-19 patients). The basic premise is: keep the virus off your skin. In areas of large amounts of secretions take extra precautions. Cover everything; mouth and nose through use of N95 mask, hair, face, skin on face and neck, clothes, hands and boots. Single coveralls are probably more efficient than piecemeal additions. However, the barrier protections should prevent COVID-19+ secretions and droplets from making direct contact with the skin of the healthcare worker’s face and neck where the hand can/will transfer virus to the airway. Other parts of the body should also be considered as a reservoir, depending upon the degree of secretion exposure.
Removing protective gear is critical and often the source of contamination of the healthcare worker. The CDC has excellent donning and doffing materials available. Initially designed for the Ebola outbreaks, they thoroughly go over the processes of donning and doffing protective equipment to minimize exposure. It is highly recommended that individuals caring for COVID-19+ patients review the processes in order to minimize their risk for exposure to respiratory and bodily secretions. (videos on Youtube and materials on Donning: https://www.cdc.gov/HAI/pdfs/ppe/ppeposter148.pdf, doffing: https://www.cdc.gov/vhf/ebola/hcp/ppe-training/n95respirator_coveralls/doffing_01.html)
Barrier protection choices: The more likely that your skin will be exposed to COVID-19+ fluids (ER in pandemic, ICU, airway intubation/extubation, OR, COVID-19 unit are high risk), one should attempt to minimize skin exposure with the fewest possible gaps in coverage (face, neck, hair, feet etc). Start with clean skin, clean scrubs and shoes/clogs limited to hospital use. The donning of PPE should start with respiratory/mask barrier and then the physical barriers between you and the outside world. In high risk zones, do not remove or break the barrier until ready to end the shift. While providing care, it is appropriate to routinely change outer gloves and decontaminate instruments and inner gloves with antiseptic wipes, but do not break protective coverage of the skin/clothes. At the conclusion of the time in a high exposure zone, a formal doffing of PPE is required. If it is necessary to utilize the bathroom, the doffing and donning procedure will need to be repeated. It is during the removal of the garment that the risk for self-contamination is significant. After doffing the PPE, reclean/wash your skin and put on fresh scrubs. If there is limited availability of PPE it may be necessary to become more creative.
Hospitals are high concentration areas for COVID-19 people. Wear a mask and keep your hands clean. Frequent surveillance for possible infected persons with placing a mask on the individual will help to diminish viral environmental load.
The ultimate goal for disease prevention is to limit the inhalation of viral particles and prevent large numbers of virions on the skin that can be introduced into the mouth and nose. While it is felt that the respiratory route is the most common source of transmission, surface/hand contamination of respiratory track is feasible.
Much was learned during the SARS epidemic when another coronavirus caused significant disease and death. Below is the practice in a Hong Kong pediatric center during the SARS epidemic. The ultra high risk area is for known coronavirus patients or highly suspected infection with a patient having fever and contact with a SARS patient. The high risk area was for all other febrile admissions, but without known SARS contacts and other admissions to the hospital and the moderate risk was defined as seeing patients in the out-patient clinic. Note the changes in protective measures in the different settings:
Using this protocol with effective donning and doffing oversight, no staff or visitor acquired known infections. It is feasible to prevent acquisition of respiratory infection in the midst of an outbreak, but strict adherence to personal protection is necessary. Be safe.
- Physical interventions to interrupt or reduce the spread of respiratory viruses. Cochrane database of systemic review (Online). July 2011
- van der Sande M, Teunis P, Sabel R, “Professional and Home-Made Face Masks Reduce Exposure to Respiratory Infections among the General Population” PLoS ONE 3(7): e2618. doi:10.1371/journal.pone.0002618
- 4Radonovich LJ, et al “N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel, A Randomized Clinical Trial”. JAMA. 2019;322(9):824-833.
- 5Leung TF et al “Infection control for SARS in a tertiary paediatric centre in Hong Kong” J Hosp Infect 2004; 56: 215-222.
- 6Viscusi DJ et al “Evaluation of Five Decontamination Methods for Filtering Facepiece Respirators” Ann. Occup. Hyg., Vol. 53, No. 8, pp. 815–827, 2009