25 minute read
COVID-19: New Considerations for Respiratory Protection in Dental Practice
Bruce L. Whitcher, DDS
ABSTRACT Dentistry has been identified as a “very high-risk” occupation due to the risk of SARS-CoV-2 transmission via aerosol-generating procedures, which are integral to the practice of dentistry. This makes respiratory protection a concern for every practicing dentist, their staff and their patients.
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AUTHOR
Bruce L. Whitcher, DDS, practices oral and maxillofacial surgery in Paso Robles, Calif. He served as a member of the Dental Board of California from 2009 to 2019, serving on the licensing, enforcement and anesthesia committees as well as on the Dental Assisting Council. Dr. Whitcher is a past CDA trustee and a past member of the California Association of Oral and Maxillofacial Surgeons board of directors, serving as president in 2007. Conflict of Interest Disclosure: None reported.
On July 13, 2020, Gov. Gavin Newsom announced statewide restrictions to again halt all indoor dining and close bars, movie theaters, zoos and museums. In addition to these restrictions, more than 25 counties, including Los Angeles, were forced to close gyms, places of worship, hair salons, malls and nail salons. On Aug. 22, 2020, California reported 644,751 confirmed positive cases of COVID-19, the most of any state. [1] This includes 5,920 new cases representing a 0.9% increase. California’s positivity rate — a key indicator of community spread (the positivity rate is the percent of tests that come back positive) — is at the time of this writing 5.7% and decreasing. Hospitalization rates are also decreasing in the 14-day average, with 4,890 new hospitalizations reported for a 3.3% decrease and a 2.1% decrease in ICU patients.
As of Aug. 21, 2020, a total of 11,686 deaths were attributed to COVID-19 in the state. There is currently no vaccine to prevent COVID-19. The best way to prevent illness is to avoid being exposed to this virus. The virus spreads mainly from person to person between people who are in close contact with one another (within about 6 feet). This occurs by respiratory droplets produced when an infected person coughs or sneezes. These droplets can land in the mouths or noses of people who are nearby or can possibly be inhaled into the lungs. Surfaces can also transmit infection. Older adults and people who have severe underlying medical conditions such as hypertension, obesity (BMI > 30), heart or lung disease, diabetes, chronic kidney disease, sickle cell disease or immunocompromised systems seem to be at higher risk for developing more serious complications from the COVID-19 illness. [2]
The differences in health outcomes related to COVID-19 are most stark in COVID-19 deaths. We have nearly complete data on race and ethnicity for COVID-19 deaths, and we are seeing the following trends: Latinos, African Americans and Native Hawaiians and Pacific Islanders are dying at disproportionately higher levels. More males are dying from COVID-19 than females, in line with national trends. [3]
In early July, some California counties began utilizing the “attestation process” to certify that the spread of COVID-19 was under control locally. To qualify, counties had to prove they had stable hospitalizations, COVID-19 cases on the decline, adequate contact tracing and other criteria.
In response to the increasing numbers of cases, the state created a monitoring list of counties where COVID-19 trends were particularly concerning. It started with about a dozen counties at the end of May. As of late July, more than half of California counties were on the monitoring list. On July 13, 2020, the state health director issued an order to require specified indoor businesses to cease operations. In addition, counties that remained on the county monitoring list for three consecutive days were required to shut down specified industries including gyms, fitness centers, places of worship, personal care services and other activities unless they could be modified to operate outside. Due to difficulties with data transmission from testing laboratories to the California Reportable Disease Information Exchange (Cal REDIE) tracking system, the county monitoring list was frozen between Aug. 1 and Aug. 16. There was considerable concern about the effects of inadequate transmission of testing data on COVID-19 case statistics because this affected the day-over-day reported case data. [4] The backlog of 300,000 cases was quickly cleared by collaboration between the California Department of Public Health (CDPH) and the California Department of Technology (CDT) and was most likely the result of overburdened data management systems.
Government Oversight
Several state and federal government agencies provide guidance or oversee the health care workplace, including the Centers for Disease Control and Prevention (CDC), Occupational Health and Safety Administration (OSHA), Cal/OSHA, CDPH, the Dental Board of California and international organizations such as the World Health Organization (WHO).
CDC Recommendations for Dental Care
The CDC recommends respiratory protection during treatment of patients with suspected or confirmed COVID-19 disease and that these patients should receive medically necessary emergency dental care according to the CDC’s Interim Infection Prevention and Control Recommendations for Patients with Suspected or Confirmed Coronavirus Disease 2019 (COVID-19) in Health Care Settings. [5] The decision to treat these patients should be made in conjunction with the patient’s medical provider to determine the appropriate setting for care.
Due to evidence of transmission by asymptomatic individuals, the CDC recommends that during aerosolgenerating procedures (AGPs) conducted on patients assumed to be noncontagious, dental health care workers (DHCWs) should use an N95 respirator or a respirator that offers a higher level of protection such as other disposable filtering facepiece respirators, powered air purifying respirators (PAPRs) or elastomeric respirators, if available. [6]
Respirators should be used in the context of a respiratory protection program, which includes medical evaluations, training and fit testing if necessary. Of note, it is uncertain if respirators with exhalation valves provide source control though they provide adequate respiratory protection for the DHCW. Cal/OSHA approves their use during respirator shortages and recommends using a full-face shield to deflect expiration. If a respirator is not available for an AGP, use both a surgical mask and a full-face shield. Ensure that the mask is cleared by the U.S. Food and Drug Administration as a surgical mask. Use the highest-level mask available. If a surgical mask and a full-face shield are not available, do not perform any AGPs.
CAL/OSHA
The California Division of Occupational Health and Safety (Cal/OSHA) is the state’s agency that regulates employee safety under the California Department of Industrial Relations. Unlike the CDC, Cal/OSHA has enforcement authority and may carry out workplace inspections.
Cal/OSHA recently proposed new industry guidance for dentistry. An early version is similar to CDC and OSHA guidance published to date.
OSHA
OSHA has identified dentistry as a “very high-risk” occupation due to the risk of SARS-CoV-2 transmission by AGPs utilized during dental practice. [7] AGPs are integral to the practice of dentistry, making respiratory protection a major concern for every practicing dentist, their staff and their patients. Although the CDC, OSHA, CDPH and others have indicated that wearing an effective N95 mask or, under some circumstances, an approved Level 3 surgical mask provides adequate respiratory protection, these guidelines recommend use of the highest level of respiratory protection available for highrisk procedures. The CDC currently recommends that dentists not treat known or suspected COVID-19 patients in a dental practice setting because they typically lack a negative-pressure room to contain virus spread. To date, the CDC reports no cases of clinical transmission due to dental treatment. Dentists may wish to consider whether a higher level of protection is advisable for procedures that generate significant amounts of aerosol, may involve mucosa with a high viral load or where the duration of exposure is extensive.
Until more is known about how COVID-19 spreads, OSHA recommends using a combination of standard precautions, contact precautions, airborne precautions and eye protection (e.g., goggles, face shields) to protect health care workers. []8
OSHA regulations require that respirators appropriate for workplace safety must be provided through a respiratory protection program. Any employee using a respirator voluntarily must be medically able to use that respirator. The respirator must be cleaned, stored and maintained so that its use does not present a health hazard to the user. The employer shall designate a qualified program to administer or oversee the respiratory protection program and conduct the required evaluations of program effectiveness. The employer shall provide respirators, training and medical evaluations at no cost to the employee.
OSHA specifies that the employer shall provide a powered air-purifying respirator (PAPR) if the medical evaluation finds that the employee cannot use a negative-pressure respirator; if a subsequent medical evaluation finds that the employee is medically able to use a negative-pressure respirator, then the employer is no longer required to provide a PAPR. A negative-pressure respirator means any tight-fitting respirator in which the air pressure inside the facepiece is negative during inhalation with respect to the ambient air pressure outside the respirator. The disposable N95 filtering facepiece respirator is a negative-pressure respirator. OSHA requires fit testing for negative-pressure respirators. [9] Nearly all PAPRs are positive-pressure respirators that use a blower to provide clean filtered air; PAPRs do not require fit testing.
Review of SARS-CoV-2 Transmission Among Dental Health Care Workers
Reports of SARS-CoV-2 transmission to health care workers appeared early in the pandemic. By the end of January 2020, 11 hospitals in Wuhan, China, had reported over 15 confirmed cases among health care workers. [10] Unfortunately, a substantial number of health care workers were infected in health care settings before the end of January 2020. On Feb. 24, 2020, the WHO-China Expert Group conference stated that a total of 3,387 infected cases (2,055 confirmed cases, 1,070 diagnosed cases and 157 suspected cases) were health care workers in 476 health care settings, of whom 3,062 were in Hubei, China (90.4%). Although SARS-CoV-2 itself is significantly infectious, it should not be held fully responsible for the extensive spread of the infection. In fact, the main reasons for earlier virus transmission to health care workers were due to lack of awareness of adequate protection of health care workers and leaders in health care settings, and later transmissions were the result of an insufficient supply of PPE. [9]
The risk of SARS-CoV-2 transmission to DHCWs by aerosolgenerating dental and medical procedures was identified early in the pandemic. The Center for EvidenceBased Stomatology, School and Hospital of Stomatology, Wuhan University in Wuhan, China, reported nine cases of COVID-19 among 169 staff members after treating more than 700 patients at their facility since January 2020. [11] There have been no further cases among colleagues or patients who had close contact with them. According to analyses of epidemiologic investigation and medical history, all of these cases are without documented association, except two nurses from the same department (patients 2 and 3), one of whom (3) had been in contact with a family member with COVID-19. For cases 1 and 2, the staff and the student with confirmed COVID-19 stated that they did not contact one another closely, and most of them had been away since Jan. 22 or 23, 2020, because of the Chinese Spring Festival. These cases were therefore determined unlikely to result from cross infection among staff members.
Treatment at this facility was limited to dental emergencies and utilized infection control measures that included prescreening patients for signs and symptoms of COVID-19. The lack of transmission among staff members was attributed to the use of PPE, including masks, gloves, gowns and goggles or face shields. As respiratory droplets are the main route of SARS-CoV-2 transmission, N95 masks were worn in clinical treatment areas. []
A report from Zhejiang University Hospital in Hangzhou, China, reported no cases of COVID-19 transmission in the dental setting but described the difficulty of identifying asymptomatic patients who may carry and transmit the virus. 11 In addition to the “standard precautions,” the authors recommend specific precautions for dental practices to reduce the risk of transmission of SARS-CoV-2 that can be applied in dental care settings during this outbreak. These recommendations are based on the COVID-19 interim guidance set forth by the WHO (2020) and current clinical practice in China.
It remains unclear if any DHCWs are being infected in the work setting despite effective droplet precautions as opposed to those who are infected because of inadequate PPE. Wang et al. [14] suggest that the considerable number of early health care infections and deaths may have been due to a combination of inadequate PPE due to lack of awareness early in the epidemic, large-scale exposure to infected patients, shortage of PPE and inadequate infection prevention training.
WHO Guidance
WHO guidance on infection prevention and control of acute respiratory infections includes a discussion of the significant knowledge gap regarding AGPs and the lack of agreement as to which procedures should be included. Guidance is based on the widely referenced systematic review by Tran et al. [15] that identifies tracheal intubation as the only procedure that is consistently associated with SARS transmission. At present, no guidelines can be established based on specific evidence of infectivity of SARS-CoV-2 during AGPs. This knowledge gap leaves clinicians unsure whether procedures are safe to undertake. Lack of clarity of risk may in turn lead to preventable infections of health care workers if procedures are undertaken without appropriate PPE or to worse outcomes for patients if procedures are withheld due to safety concerns. [16,17]
AGPs are performed worldwide in oral health care settings. AGPs are defined as any medical, dental or patient care procedure that results in the production of airborne particles < 5 μm in size that can remain suspended in air, travel over a distance and may cause infection if they are inhaled. The risk of airborne COVID-19 transmission when AGPs are performed can therefore not be excluded.
Management of AGPs in the COVID-19 Era
It is likely that there is a hierarchy of AGPs in the sense that each will convey a different degree of risk of infection transmission. It is generally advised that for AGPs in addition to standard precautions, patients suspected or known to be infected with SARS-CoV-2 should, if possible, be treated in a negative-pressure room, that health care workers (HCWs) should always wear a gown, gloves, face shield and goggles and an N95-level mask and that these procedures should only be undertaken when absolutely necessary. [18]
Givi et al. [19] suggest that health care workers should consider using PAPRs for certain high-risk ear, nose and throat aerosol-generating medical procedures performed on patients with probable or confirmed COVID-19.
Does Airborne Transmission of SARS-CoV-2 Occur?
The role of airborne transmission of SARs-CoV-2 is debated extensively in the literature. [20] WHO guidance indicates that the possibility of airborne transmission during dental procedures cannot be excluded. Much remains unknown about whether the aerosolized virus is infectious and what amount of virus one needs to be exposed to become sick, known as the minimal infectious dose. Even if aerosol transmission does occur, it is not clear how common it is compared with other transmission routes, such as droplets or surfaces. [21] It has been shown that SARSCoV-2 can survive in aerosols for at least three hours (with a similar reduction in titer as occurs with SARS-CoV-1). This does not confirm airborne transmission, but it establishes that airborne transmission is feasible and supports comparisons between SARS-CoV-2 and SARS-CoV-1 transmission routes.
Testing
Is preprocedural laboratory testing for COVID-19 advisable to apply more effective use of PPE for respiratory protection? Depending on testing availability and how rapidly results are available, facilities may consider implementing preadmission or preprocedure testing for COVID-19, which might inform implementation of PPE for respiratory protection, especially in the situation of PPE shortages. However, limitations of this approach should be considered, including negative results from patients during their incubation period who could become infectious later and false negative tests depending on the test method used.
Due to difficulties with contact tracing, the CDC has advised facilities to consider forgoing formal contact tracing and work restrictions for DHCWs with exposures in favor of universally applied symptom screening and source control strategies.
HCWs who have been present in a room during an AGP for a patient with COVID-19 while not wearing the full complement of PPE, such as a gown, gloves, eye protection and a respirator, are classified as having high-risk exposure and should be excluded from work for 14 days and monitored for symptoms. HCWs who were in the room during an AGP while wearing the full complement of PPE, such as a gown, gloves, eye protection and respirator, do not need to be placed on work restrictions but should be monitored for fever and symptoms of COVID-19. [18]
Data are insufficient to precisely define the duration of time that constitutes a prolonged exposure. Until more is known about transmission risks, it is reasonable to consider an exposure of 15 minutes or more as prolonged. However, any duration should be considered prolonged if the exposure occurred during performance of an aerosol-generating procedure (TABLE, "Respirator Selection Guide for Aerosol Transmissible Diseases", SEE TABLE IN FULL ISSUE OF THE JOURNAL ).
Do PAPRs, Elastomeric Respirators or N95 Filtering Facepiece Respirators Provide Greater Protection?
PAPRs, reusable elastomeric respirators and filtering facepiece respirators (e.g., N95 masks) represent different methods of filtering out aerosols in the air. Although cost estimates vary, a PAPR has the highest initial cost, as much as $1,400. A PAPR [22] contains a battery-powered, high-efficiency particulate air filter that delivers clean air into a hood or a full-face mask and blows off exhaled air. The hood is either hard and tight fitting or loose. The risk of leakage with PAPRs is negligible and, unlike reusable elastomeric respirators and N95 masks, there is no need for a fit test or additional eye protection because the head is completely enclosed within the system. This feature of the PAPR benefits individuals who fail fit tests and those whose religious beliefs prevent them from shaving. Decontamination protocols for PAPRs must be in place and adhered to meticulously before they are reused.
Reusable elastomeric respirators, which typically cost less than $100, are used more commonly in heavy industry than health care. Such devices are made to meet National Institute for Occupational Safety and Health (NIOSH) standards and are defined by the ability of the device to filter out oil or nonoil particulate. They may either cover the lower half of the face (and require additional eye protection) or cover the entire face. [23] Like PAPRS, they are not often used in dentistry, but have advantages over the N95 for high-level respiratory protection, including a single fit test, lower long-term costs because only the filters are replaced, more comfort breathing especially over long periods and can be reused for future aerosol transmissible disease protection. [24]
Respirators are classified according to their particulate filtration efficiency. Both reusable elastomeric respirators and filtering facepiece respirators come in N100 (99.7%), N99 (99% filtration efficiency) and N95 (95% filtration efficiency) varieties. An “N, R or P” prefix indicates the relative resistance to oil. A highefficiency filter has at least 99.7% efficiency and is found only in PAPRs. The familiar N95 mask can cost more than $10 each, and the cost is highly dependent on availability. In addition, the cost of annual fit testing can be substantial and there have been persistent problems with the availability of quality N95 masks. The use of PAPRs could help alleviate N95 supply chain problems until production of N95 masks can be increased to meet the demand. [22] Although PAPRs have long been used in hazardous industrial environments and to some extent in hospital and medical research environments, they are a new option for hazard reduction in dentistry. A combination of N95 masks and PAPRs is being used in some health care facilities to help overcome shortages of masks. [26] Other facilities have successfully adopted a PAPR-only approach when there is an ongoing need for respiratory protection.
No studies exist that directly compare the different respirators’ abilities to prevent transmission of viral illness in the health care setting. Such studies would need to incorporate doffing and reprocessing procedures in the experimental design because there is high risk of transmission if doffing is performed incorrectly, and the risk may be modified by the type of PPE used.
Experimental studies in the occupational health literature compared how well different respirators filter aerosols (typically sodium chloride aerosols) in simulated industrial environments. Respirators are assigned a protection factor (APF) that is a measure of the ratio of airborne contaminant inside and outside the respirator. [23] The APF for PAPRs is usually 25 versus 10 for filtering facepiece respirators, 10 for half-mask elastomeric respirators and 50 for full-facepiece elastomeric respirators. Higher APFs from 1,000 up to 10,000 are usually assigned to atmosphere supplying systems such as supplied air systems (SARs) and selfcontained breathing apparatus (SCBA) designed for immediately dangerous to life or health (IDLH) environments.
A major risk with filtering facepiece respirators and reusable elastomeric respirators is that the airtight seal can leak during a procedure, compromising their performance. In a study of eight subjects each tested on six different N95 masks, thermal imaging showed that leakage (mainly in the nasal and malar regions) occurred in all failed leak tests and the majority (26 of 35) passed fit tests. The risk of leakage would be expected to increase with the length of time the N95 mask is worn, for example, during long cases. [25]
There is concern that the unfiltered exhaust from PAPRs may increase the risk of transmission of virus particles to patients from users who are unknowingly infected with COVID-19, but this risk would likely be diminished if PAPR users wore surgical masks. PAPRs may be cumbersome to use, may fog up and prevent the use of headlights, but these concerns are also true of masks, face shields and goggles.
The balance of evidence suggests that PAPRs and full-facepiece elastomeric respirators, when properly used, doffed and reprocessed, would be expected to reduce the risk of transmission of infection and/or severity of illness by reducing exposure during high-risk cases compared to N95 masks. Cost-effectiveness studies comparing different respirator types have not been performed, but it may be feasible for some dental practices to acquire a limited number of PAPRs for use during high-risk procedures. One of the challenges facing those considering using a PAPR is that very few dentists have experience using them. This limits the exchange of information among colleagues that traditionally occurs when dentists consider purchasing a new piece of equipment or adopting a new technique. Although a handful of manufacturers have provided virtual demonstrations of PAPRs for use in dentistry, this is a limited form of evaluation and does not give the dentist considering an expensive piece of equipment the opportunity to “try before they buy.”
In 2015, the Institute of Medicine convened a symposium to review the use of PAPRs in several medical facilities. [24] We interviewed for this article three dentists about their experience wearing PAPRs. They reported an experience similar to findings from this symposium that includes several studies of PAPRs conducted by the Veterans Administration (VA). [26] California dentists reported that PAPRs were more comfortable than an N95 mask worn with a face shield and other PPE, but that at times there were difficulties with missing PAPR components. Donning and doffing the units requires a trained assistant. Users experienced some difficulty with communication due to reduced hearing and some had heavy air-supply units that were difficult to wear for long cases. In addition, one dentist experienced drying of the cornea due to the constant flow of air from the supply duct.
VA employees found PAPRs more comfortable than half-face elastomeric masks or N95 respirators. However, among a variety of respirators studied, none of the tested devices were well tolerated for an entire eight-hour shift by all test participants. In one 2009 study, half of the study subjects had removed their respiratory protective device by the end of an eight-hour work shift, regardless of the type of respirator used. VA researchers found that PAPRs were primarily disliked, not because they were uncomfortable but because they might interfere with occupational activities and might be somewhat challenging to use in certain situations.[26] The major challenge with respirators lies not in designing an effective one, but in persuading people to wear it and to wear it correctly. Respiratory training is not taken as seriously as bloodborne pathogen training even though both promote a safe health care workplace.[26]
All respiratory protection devices have advantages and disadvantages. The major advantage of PAPRs is that many types do not require fit testing. It is estimated that close to 10% of workers cannot be fitted for an elastomeric or N95 respirator due to facial hair or other reasons. Another advantage to using PAPRs is their reusability. The major disadvantages are maintenance and cost. Disposable N95 respirators, while costing much less for an individual respirator, are not as economical if workers need to use respirators day after day for weeks during a pandemic. Other disadvantages that will have to be overcome before PAPRs become common alternatives for respiratory protection in dentistry include auditory communication, comfort, reduced bulk, headlight accommodation, airflow control and ease of donning and doffing.
The increasing risk of SARS-CoV-2 transmission now facing the public at large as well as the dental profession bears a striking similarity to the emergence of bloodborne pathogens as a health and safety issue during the AIDS epidemic of the 1980s. Although the transmission of bloodborne pathogens was and continues to be extremely rare, the profession quickly adopted enhanced infection control practices based on CDC guidance, primarily to reduce the risk of disease transmission and improve the quality of care for patients as well as to protect the health of DHCWs. At one time, glove wearing, eye protection and instrument sterilization were viewed as obstacles to the practice of dentistry, but infection control is now considered fundamental to the standard of care. The adoption of infection control in the 1980s conveyed an important message to the public: The dental profession makes patient safety its highest priority.
We may be experiencing now the same kind of shift in thought required by the AIDS crisis. We submit that one day, improved respiratory protection through the use of PAPRs in dentistry may also become commonplace and may eventually be considered integral to the practice of dentistry.
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THE AUTHOR, Bruce L. Whitcher, DDS, can be reached at whitcher.bruce@gmail.com.
