Should Respiratory Protection Be Used In All Anorectal Operations That Generate Smoke?

The current coronavirus disease 2019 (COVID-19) global pandemic has led to an increased demand for personal protective equipment and, specifically, an increased demand for N95 respirator masks. The consequence of this has been the limited availability for use of N95 respirator masks in protecting health care workers. To counteract this shortage, the White House and the Secretary of Labor have instituted steps to increase the availability of respirators.¹ The shortage of N95 respirator masks and these measures have caused our group both to examine why we use respiratory protection during cases such as high-resolution anoscopy or fulguration of anal condyloma, and to reconsider the use of personal protective equipment during anorectal surgery, in general.

Approximately half of the US population carries the genital form of human papillomavirus (HPV), with the prevalence in adults being 42.5%; and 22.7% of the population carry high-risk viral types.² Electrosurgery, laser ablation, and ultrasonic scalpel dissection use energy to destroy tissue which creates a gaseous by-product commonly referred to as surgical smoke or plume. This smoke can contain viable cells³ and viruses⁴; specifically, the presence of HPV in this smoke has been demonstrated.^5,6 Human papillomavirus in smoke does pose a risk of infection, with animal studies showing transmission of papillomavirus between individuals via a surgical smoke plume.⁷ In an actual clinical setting, although the presence of HPV from surgical smoke has been demonstrated in the surgeon’s nasopharynx,⁸ true transmission appears rare and confined to case reports.⁶ Yet even though this risk is rare, extrapolating from the prevalence of disease and known components of smoke, about half of all anorectal operations using electrocautery have HPV present in the surgical smoke. As such, standard surgical masks may not be adequate protection in these cases.

Current Occupational Safety and Health Administration standards on control of air with potentially harmful substances state that “surgical masks used to prevent contamination of the patient are not certified for respiratory protection.”⁹ Major factors contributing to the efficacy of masks or respirators in providing adequate protection are: size of particles that may transmit disease, filtration performance, and seal against the wearer’s face. Most particles in surgical smoke are less than 1.1 μm in diameter,¹⁰ with viruses specifically ranging from 0.01 to 0.3 μm in size. Standard surgical masks are able to filter particles roughly 5 μm in diameter, making them inadequate to filter most of the particles in surgical smoke.¹⁰ The efficiency of these masks to filter particles of this size is also quite variable and can range from less than 10% to nearly 90% for different manufacturers when tested using standard parameters for certification.¹¹ Seal is also lacking in surgical masks, because they are designed not to be tight-fitting, further contributing to ineffectiveness. Respirators are an alternative to surgical masks. Respirator filtration performance is measured using an aerosol of 0.3-µm latex spheres. The subsequent rating is based on the percent of these particles filtered; for example, those that collect at least 95% of the challenge are given a 95 rating. These respirators are also rated as “N” if they are not resistant to oil, “R” if somewhat resistant to oil, and “P” if strongly resistant.¹¹ For fit, these respirators are also superior to surgical masks and designed to minimize the degree of leakage around the face piece. Given these factors, respirators of at least N95 grade or greater likely provide better protection against HPV particles in surgical smoke than a standard surgical mask.¹¹

In addition to personal protective equipment, surgical smoke evacuation techniques can provide additional means of protecting operating room staff from potential harmful effects of surgical smoke. These measures include ensuring that operating room air circulation and exchange is adequate, and the room is maintained at a positive pressure. Wall suction may be used to evacuate smoke; however, if the suction does not use an in-line filter, it will not provide any protection. Specifically designed smoke evacuation systems have several features that make them advantageous for mitigating smoke exposure. The distance between a suction device and the smoke has a large impact on the amount of particles captured because smoke disperses rapidly. To counteract this dispersion, the closer to the plume the device is, the more smoke is captured with an evacuator at full power capturing 99% of smoke at 1 inch from the source versus 53% when placed 3 inches from the smoke source.¹² The rate of capture is also dependent on the airflow across the device, which is a product of many factors such as resistance of the filter, tubing diameter, and suction power. A recommended minimum air flow of 25 to 35 cubic feet per minute is currently recommended.¹² Even with adequate evacuation and smoke capture, appropriate filtration is essential to sequester any hazardous particles from air that may be recirculated into the operating room. Commercially available systems often use an ultra-low particulate air filter that removes 99.9% of contaminants larger than 0.12 µm.¹²

Despite the data, it is still common practice to reserve the use of N95 respirator masks and smoke evacuation devices to cases with known HPV or condyloma. However, given the high prevalence of HPV and its presence in surgical smoke, we believe all anorectal surgery should be viewed as a case with HPV or condyloma, because about half of patients will have HPV. As such, picking and choosing which cases to use respiratory protection and smoke evacuation defies this logic. If you are confident in the data and the potential risks, then N95 respirator masks and smoke evacuation devices should be used in all anorectal cases generating smoke. If you do not, they should never be used, and the personal protective equipment and resources should be spared.