Authors: Stanislas Chaussade, Anna Pellat, Ali Chamseddine, Felix Corre, Romain Coriat
Categories: Endoscopy, SARS‐Cov2, ambulatory unit, colonoscopy, endoscopy, transmission, Review Article
Source: United European Gastroenterology Journal
Doi: 10.1002/ueg2.12355
The SARS‐Cov‐2 disease disrupted essential hospital procedures, such as gastrointestinal (GI) endoscopy, due to concerns about air transmission and the risk of exposing health care workers. With the spread of the pandemic, air transmission was considered as the main source of SARS‐Cov2 transmission. This raised the problem of transmission by aerosolization of viral particles in operating rooms as well as endoscopy units. This is in line with the known airborne transmission of many other respiratory viruses. The risk of SARS‐Cov‐2 transmission during GI endoscopy was initially reduced by controlled measures, involving personal protections (mask…), restricted access to endoscopy rooms, and detection of infected patients. Gastrointestinal endoscopy generates aerosols, which may carry viruses. In addition, the endoscopy system may facilitate the diffusion of virus particles or fomites considering the forced‐air cooling system used to maintain a stable temperature inside the box (25°C). The volume of air that goes through the light source box is high (240–300 m^3^ for a 1‐h period). Moreover, the light system contains an air pump to inflate air inside the gut lumen. In order to isolate people from hazard, different levels of protection and solutions to avoid airborne transmission of microorganisms should be proposed, such as the reinforcement of personal protective equipment, the change in the way people work and engineering control of the risk.
Keywords: ambulatory unit, colonoscopy, endoscopy, SARS‐Cov2, transmission
The global outbreak of Coronavirus disease 2019 (COVID‐19 or SARS‐Cov‐2) has been characterized as a pandemic by the World Health Organization (WHO) on 11 March 2020 COVID‐19 has disrupted hospital procedures, such as gastrointestinal (GI) endoscopy. It was due to concerns about the risk of exposing health care workers (HCW) and the insufficient level of preparation to such pandemic in western country. ^1^ , ^2^ The first published data on COVID‐19 proposed common routes of direct transmission through droplets and indirect transmission through direct or indirect contact with contaminated surfaces. The route of contaminated surface is now considered less likely to occur. Now on, the transmission route is more a direct transfer via respiratory droplets, when coughing, sneezing or saliva, via direct person‐to‐person transmission. ^3^ With the spread of the pandemic and the emergence of more aggressive variants, air transmission was suspected in July 2020 and is now considered as the main source of SARS‐Cov2 transmission. Such hypothesis is in line with the airborne transmission of many other respiratory viruses, such as SARS‐CoV‐1, Middle East respiratory syndrome–Co, influenza virus, respiratory syncytial virus and non‐viruses such as mycobacteria and fungi. ^3^ This raised the hypothesis of air transmission of viral particles in hospitals. The presence of the SARS‐CoV2 have been identified in surgical smoke during laparoscopy leading to the recommendation to use smoke aspiration and filtration to avoid air contamination in the surgical room. Controversy surrounding how COVID‐19 is transmitted and what interventions are needed to control the pandemic has revealed a critical need to better understand the airborne transmission pathway of respiratory viruses and to propose measures for prevention of transmission. ^4^ , ^5^ Not surprisingly, SARS‐CoV‐2 RNA has been identified in air samples from rooms or wards housing unmasked patients with COVID‐19. ^6^ Meta‐analysis suggested that there is association between face mask use and reduction of COVID‐19 paving for the impact of infected respiratory droplets. ^7^ Few studies has been done on the risk of airborne transmission in the endoscopic room. European Society of Gastrointestinal Endoscopy and American Society for Gastrointestinal Endoscopy recommendations did not stressed the risk of microorganisms' airborne transmission. Endoscopes used in gastroenterology has a unique system to inflate air in the lumen of the gut. Meantime, it has been demonstrated that the gut and specially the small intestine epithelium have receptors allowing the entrance of the virus in the body. A better knowledge of airborne transmission in the endoscopic room is warranted to propose strategy to prevent the risks of transmission of respiratory infections during digestive endoscopy and to avoid the risk of contamination of patients and HCW.
Early in the COVID‐19 pandemic, it was assumed that droplets and fomites were the main transmission routes based on the relatively low basic reproduction number. Initial recommendations have focused mainly on protection against droplets and fomite transmission, whereas the airborne route has not been considered. The airborne transmission was suspected later and is now considered as the main way of transmission with the emergence of new variants. The “airborne transmission” definition was referred to the inhalation of infectious aerosols, defined to be smaller than 5 μm, and traveling for a distances of more 1–2 m away from the infected individual. ^3^ In fact, respiratory aerosols are produced during all expiratory activities, including breathing, singing, coughing or sneezing and during some medical procedures such tracheal intubation, oropharyngeal aspiration or otolaryngology surgery (ENT). It has recently been suggested that the distinction between airborne and droplets transmission was artificial and there was a continuum between particle size and the duration of aerosols in the air. Residence time of aerosols of varying size in air can be estimated for spherical particles. Particles sized more than 100 μm can remain suspended in air for more than 5 s from a height of 1.5 m. Particles are able to travel beyond 1 m from the infected person. ^3^ Particles sized more than 1 μm can remain suspended in air for more than 12 h from a height of 1.5 m and are able to travel beyond several meters from the infected person. From an infected person, those aerosols are able to accumulate virus in poorly ventilated spaces. Smaller aerosols have shown higher pathogen concentrations than droplets when both were measured. ^8^ The risk of transmission is link to the quantity of virus, which is related with the duration of the stay into the endoscopy room by infected persons. In hospital setting, close contacts between an infected patient and HCW are the most common way to catch the virus that causes COVID‐19. The infectivity of virus‐laden aerosols will depend of their properties, including physical size, viral load, infectivity, and airflow velocities. ^3^
Nosocomial outbreak of SARS‐COV2 infection have been described suggesting aerosol transmission across long and short distances. ^9^ Aerosol generating procedures (AGP) are a risk factor of nosocomial transmission of SARS‐Cov2. Aerosol generating procedures are considered as a risk factor of transmission of SARS‐Cov2 and it have been highlighted to require a higher grade of personal protective equipment (PPE) during the pandemic. Aerosol transmission has been suggested with the new variants (alpha, delta and omicron). It explained the higher risk of transmission observed with those variants. Aerosol generating procedures also promote long‐range transmission from inhalation of small infectious respiratory particles that remain suspended in air for long periods.
The persistence of virus particles in aerosols and its infectivity will also depend of environmental factors such temperature, humidity, airflow and ventilation. Such situations help to an inhalation of a virus by non‐infected persons and favor the spread of the virus. Endoscopy room and digestive procedures aggregate a poorly ventilated zone and a medical procedure at risk of spreading viruses. It call for taking into consideration the air circulation of an endoscopy room.
A recent review demonstrated that SARS‐CoV‐2 contamination is widely found in the air and surfaces of patient and non‐patient areas of hospitals which creates a notable hazard of hospital‐associated infections by this virus. ^10^ Multivariate analyses of risk factors of SARS‐Cov‐2 transmission identified that patient areas and AGP increase the risk of room contamination, whereas patient masking decreases both air and surface‐borne SARS‐CoV‐2 contamination. ^10^ In a recent study, SARS‐CoV‐2 was found on the floor beneath the patient bed of the endoscopic room, on the endoscopy cart monitor and on the ventilator, but air contamination was not evaluated. ^10^ However, air samples containing positive SARS‐CoV‐2 particles have been detected in hospitals since the virus can remain viable in aerosols for over 3 h with an estimated half‐life of 1.1–1.2 h. ^11^ Nosocomial outbreak resulting from aerosol‐borne SARS‐CoV‐2 introduced by HCW or patients have been shown recently. These data suggest that air could be a way of transmission of respiratory virus in hospital settings. ^9^
The introduction of the endoscope through the mouth or the nasopharynx generates aerosols of particles due to insufflation, the vomiting reflex or coughing. In infected patients, an upper endoscopy may induce aerosolization of infected particles who may expose HCW or patients who came into the endoscopic room (Figure 1). In the context of the SARS‐CoV‐2 pandemic, upper and lower endoscopy were initially classified in the 10 top procedures generating an aerosol. ^12^ The top three procedures are the autopsy, the cleaning tasks and GI procedures.
FIGURE 1 Mode of transmission of SARS‐CoV‐2 in the endoscopic room.
Endoscopic procedures often need tracheal intubation and aspiration of oropharyngeal secretions which are clearly associated with a higher risk of aerosolization and which could increase the risk of air and surface contamination in the endoscopic room. ^12^ Since 2020, several studies have clearly shown that upper endoscopy was associated with aerosolization of oropharyngeal secretions and that this procedure was definitively classified as an aerosol generating procedure. ^13^ , ^14^ , ^15^ These studies showed that esophagogastroduodenoscopy and nasogastroscopy was associated with aerosol generation, especially during coughing and burping, and that sedation did not decrease the risk of aerosol generation. ^15^ Interestingly, the use of a dental sucker, which allow saliva aspiration, could reduce the number of particles expelled during the procedure whatever the size of the particle (> or <5 µm). ^14^ Whether colonoscopy is also an aerosol generating procedure is still debated. Nevertheless, viable SARS‐Cov2 viruses have been found in human feces sometimes for a longer time than in oro‐pharyngeal secretions. Such data suggested that the gut could be a reservoir of the virus. Fecal aerosol transmission has been suspected after toilet flushing through the air of the pipe of the system. ^16^ Therefore, gas or air leaks are frequently seen during colonoscopy and could lead to bio aerosolization and production of virus‐laden fecal aerosols in the endoscopic room. Another way of dissemination of SARS‐Cov‐2 in the air and close environment of the HCW is through the valve of the endoscopes. Indeed, gas and liquid leakage from the biopsy valve and device handles have been demonstrated during endoscopic procedures. ^17^
Recently, it has been suggested that the air circulation system of the endoscope could participate to the diffusion of virus‐laden aerosols and to the possible contamination of patients or HCW through the fan system and the air pump of the light box (Figure 2). ^18^ , ^19^ The light source and the processor of the endoscopic system contains many microprocessors and a lamp, which induces high temperature in the box up to 323°C for a xenon lamp. The light source temperature is controlled by a forced‐air cooling system to maintain a stable temperature inside the box (25°C). The air used by the forced‐air cooling system is sucked from the patient's closed environment through several aeration ports. The air is evacuated outside the box by several fans. The volume of air that goes through the light source box is very high (4–5 m^3^/min, i.e., 240–300 m^3^ for a 1‐h endoscopy). During a 1‐h procedure, volume of the endoscopic room is used several times to decrease the temperature inside the light box. Such system may facilitate the diffusion of virus particles or fomites outside the light box and processor and could facilitate virus' contamination.
FIGURE 2 Role of the fans of the light system and the air pump of the endoscopic system in the diffusion of virus particle induced by aerosol generating procedures (upper endoscopy, tracheal intubation…).
In addition, the light system contains an air pump to inflate air inside the gut lumen. This air pump sucks the air inside the light source box and pushes it into the air pipe and then to the distal tip of the endoscope and to the water tank. The air pump does not have a dedicated high‐efficiency particulate air filter (HEPA) to avoid transmission of microorganisms, such as bacteria and viruses. The system is located inside the processor box and he is not accessible for microbiological control. The processor and the light box cannot be cleaned and disinfected between two procedures. A contamination of the processor box will contaminated the air pump and increase the risk of a patient nosocomial infection. The infection could be a transmission of either a virus, a bacteria or fungi. All these mechanisms lead to the contamination of the endoscopic room's air and the surface close to the patient. Those transmission modes could also explain the risk of bacteria exposure of the endoscopist's face during endoscopy, which has been described before the SARS‐Cov2 pandemic. ^20^
The spread of the pandemic raised the question of the potential risk of SARS‐Cov‐2 transmission during digestive endoscopy. So far, European Society of Gastrointestinal Endoscopy recommendations have not taken into consideration the risk of airborne transmission of SARS‐Cov‐2 and other microorganisms in the endoscopic room and have failed to propose guidelines. ^21^ During the pandemic acceleration phase of the Alpha variant in December 2020 in the United Kingdom (UK), a prospective study was conducted to evaluate the risk of SARS‐Cov‐2 transmission risk during GI endoscopy. ^22^ This study identified a 1.27% and 0.65% risk rate to develop either suspicious symptoms for COVID‐19 or confirmed symptoms with a positive testing on nasopharyngeal swab respectively. Considering those numbers, controlled measures developed in the earlier pandemic phase to prevent SARS Cov‐2 infection appeared in line with the low risk of an airborne contamination. These controlled measures mainly involved personal protection (mask…), restricted access to endoscopy rooms, and detection of infected patients. Nevertheless, the second phase of the COVID‐19 pandemic, with the development of multiple mutations and variants (Delta and particularly Omicron), showed us an increased risk of transmission and particularly of air‐transmission contamination. Usage of PPE together with a vaccination against COVID‐19 might be strategy to substantially reduce the risk of SARS‐CoV‐2 transmission to endoscopy staff. ^23^ In the period of the new variants of the SARS‐Cov‐2 it appeared of interest to reassess the risk of transmission during GI endoscopy and to reinforce preventive procedures in endoscopy units.
Recent acknowledgment of airborne transmission of the SARS‐CoV‐2 by the WHO and the demonstration of SARS‐COv2 in the air of hospital rooms, reinforced the necessity of implementing protection against the air transmission route at both short and long ranges in the endoscopy room. During the initial phase of the pandemic, infection prevention and control in the endoscopy room have been effective in assuring the safety of both patients and HCW. More recently, viral variants (e.g. the Delta or Omicron variant) have shown an increased transmissibility and have become dominant drivers of the pandemic in Europe and throughout the world. This has led to uncertainty regarding infection prevention with PPE and to reinforced recommendations against aerosol transmission of SARS‐Cov‐2 or other microorganisms, especially in hospitals. In this context, different levels of protection and solutions to avoid airborne transmission of microorganisms should be proposed in order to isolate people from hazard. The first solution is PPE, the second is reinforced administrative controls to change the way people work and the third is to propose engineering control of air contamination. Engineering control seems to be the most efficient solution since it will also be useful after the end of the pandemic in order to prevent airborne transmission of other diseases as tuberculosis or fungi in the endoscopy unit.
The latest ESGE‐Nurses and Associates (ESGENA) guidelines ^17^ recommend the use of a standard surgical mask when performing an endoscopy (upper and/or lower GI endoscopy procedures) in patients with a negative polymerase chain reaction (PCR) test within 48 h before their exam. Other PPE (e.g., gloves, hair cover, protective eyewear, waterproof gowns, shoe covers…) should continue to be used. Health care facilities, such as endoscopy units, are more likely to accommodate patients infected with respiratory viruses or other microorganisms like respiratory virus, fungi and tuberculosis. Thus, HCW should be provided with proper PPE to reduce airborne exposure. Facemasks initially provided significant source control with a reduction of viral aerosols in indoor air by half, making a significant contribution to reducing the spread of COVID‐19. Recent data obtained with the new SARS‐Cov‐2 variants showed that protection with surgical masks is lower than expected ^24^ and the use of FFP2 masks is recommended during AGP. Recommendations are based on the evolutionary pressure of the virus due to variants that are able to increase the transmission rate. This emphasizes the necessity to control the quality of air in the endoscopic room by improving ventilation and filtration and to decrease all the potential route of contamination.
To maintain safe and high‐quality endoscopic practice, reinforced administrative controls and measures regarding operational reorganization of endoscopy units are also important. These measures include modification of the endoscopy unit, stockage of essential supplies, screening of COVID‐19 and other respiratory virus in patients by a mandatory questionnaire, PCR testing for COVID‐19, and limitation of HCW numbers and contact in the endoscopy unit. ^25^ Reprocessing of endoscopes and accessories should be performed according to existing guidelines. Studies have shown that SARS‐CoV‐2 is readily inactivated by commonly used disinfectants. ^26^
Airflow strongly influences the transport of virus‐laden aerosols in contrast to droplets which are rapidly deposited because of gravity. With the dominance of newer, more contagious variants, increased attention to improved ventilation, filtration and air sanitation will be important for controlling the risk of airborne disease transmission. Engineering measures to reduce aerosol concentrations through ventilation and filtration remain critical strategies for reducing airborne transmission risks in the endoscopy room. ^22^ Methods to reduce the concentration of SARS‐CoV‐2 particles in indoor air include ventilation, filtration, and disinfection. In the UK, new recommendations regarding management of operating theaters, including endoscopy rooms, were written before the COVID‐19 pandemic. These recommendations must be applied to new installations and major refurbishments of existing installations. They emphasize the need for an environmental supplied with good‐quality filtered air that is maintained at a positive pressure with respect to surrounding areas. Filtration and sterilization means coupled with high voltage alternating current systems are capable of removing airborne pathogens before entering the room or after leaving the exhaust to avoid contamination. These ventilation systems reduce airborne transmission of infectious virus‐laden aerosols in contrast to droplets. Patients on airborne precautions for possible « aerosolizing infections » shall be placed in endoscopic rooms with HEPA filters to reduce their risk of cross‐contamination (Figure 3). ^27^ Portable and commercially available HEPA air cleaners can be use without modifying the building's existing air handling system.
FIGURE 3 Role of a HVAC system with HEPA filtration system to decrease the risk of airborne transmission of microorganisms in the endoscopy room. HEPA, high‐efficiency particulate air filter; HVAC, high voltage alternating current.
Different strategies to prevent the risk of droplets and aerosol transmission of microorganisms by patients during endoscopy have been proposed. These strategies mainly involve the design of various boxes able to isolate the patient from the area close to him. ^28^ , ^29^ , ^30^ , ^31^ Theses boxes are difficult to use in routine practice but could be useful during pandemics. Another box (ENDOBOX SC) has been designed to secure the air circulation system of the endoscope in the endoscopy room (Figure 4). This box uses medical air identical to the air used by anesthesiologists for patient ventilation. The medical air is germ and viral free, cheap, and present in all operating rooms. The medical air is used to decrease the temperature induced by the air lamp and microprocessor of the light source. This medical air is also used by the air pump to inflate the gut. Endobox SC allowed inflating in the gut medical air and avoiding the diffusion of airborne particles in the endoscopic room. Finally, new design of biopsy valves and device handles are warranted to avoid the risk of contaminated aerosols and fluid particles in the close environment of patients. ^32^
FIGURE 4 Photo of the Endobox SC.
The risk of SARS‐Cov‐2 transmission during GI endoscopy is low and probably the consequence of efficient PPE by HCW. Digestive endoscopy is clearly an AGP and airborne transmission has been a major and neglected pathway for the spread of SARS‐CoV‐2 but also of many other respiratory viruses or bacteria. Although our knowledge is increasing with the occurrence of new aggressive SARS‐Cov‐2 variants, which are probably more air‐transmitted, enough is already known to justify adding reinforced measures for better protection against airborne transmission of respiratory viruses in the endoscopy room.
Recommendations from scientific societies are warranted to control the risk of airborne transmitted infections during and after pandemics or seasonal epidemics. These measures have important implications for infection‐control procedures in gastroenterology to reassure patients from a hypothetical risk of viral, bacterial or fungi transmission during endoscopy. Engineering control of air inside the endoscopic theater is a key point as well as the modification of the design of the valve and the protection of the air system of the endoscope used in gastroenterology.
Endobox patent is the property of APHP and S Chaussade. All other authors have no conflict of interest to declare.
Chaussade S, Pellat A, Chamseddine A, Corre F, Coriat R. Airborne transmission of SARS‐Cov2: what consequences for digestive endoscopy? United European Gastroenterol J. 2023;11(2):171–8. 10.1002/ueg2.12355
The data that support the findings of this study are available from the corresponding author upon reasonable request.
The data that support the findings of this study are available from the corresponding author upon reasonable request.