Negative pressure rooms and COVID-19
Sammy Al-Benna
Abstract
The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes 2019 novel coronavirus disease (COVID-19), has rapidly developed into a global pandemic and public health emergency. The transmission and virulence of this new pathogen have raised concern for how best to protect healthcare professionals while effectively providing care to the infected patient requiring surgery. Although negative pressure rooms are ideal for aerosol-generating procedures, such as intubation and extubation, most operating theatres are generally maintained at a positive pressure when compared with the surrounding areas. This article compares negative and positive pressure rooms and the advantages of a negative pressure environment in optimising clinical care and minimising the exposure of patients and health care professionals to SARS-CoV-2.
Keywords
Hospitals / Operating Rooms / Ventilation / Infection Control / Coronavirus / Severe Acute Respiratory Syndrome Coronavirus 2 / COVID-19 / Pandemics
Provenance and Peer review:Unsolicited contribution; Peer reviewed; Accepted for publication 22 July 2020.
Introduction
The recent emergence of a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has rapidly developed into a global pandemic and public health emergency (Wang et al 2020). As of 23 June 2020, a total of 9,369,381 accumulated cases and 480,095 deaths have been reported worldwide in 215 countries and regions, with an overall mortality rate of about 1% (Worldometer 2020). Coronavirus disease 2019 (COVID-19) primarily produces fever and respiratory symptoms, although involvement of other organ systems has been reported (McCloskey et al 2020). With any emerging disease, we must integrate a rapidly evolving evidence base into our understanding of the illness (Al-Benna 2020a, 2020b, Al-Benna & Gohritz 2020).
In these unprecedented times, it is critical that ventilation systems are in proper working order (Arora et al 2020, Ing et al 2020). COVID-19 has heightened this importance more than ever. Particularly in a hospital setting, certain populations are more vulnerable to airborne infections than others, including immune-compromised patients and the elderly (Nielsen 2009, Shajahan et al 2019). In addition, healthcare
professionals and visitors can also be at risk of contracting airborne diseases (Shajahan et al 2019).
Positive and negative pressure rooms
Effective positive and negative pressure rooms are an important part of healthcare facility climate control systems (Medical Advisory Secretariat 2005). In hospital settings, these rooms prevent the spread of infectious contaminants and maintain sterile or restricted spaces and are also referred to as 'protective environments' (positive pressure rooms) and 'airborne infection isolation rooms' (negative pressure rooms) (Shajahan et al 2019, Sundell et al 2011). Negative or positive pressure rooms are a necessary part of a wide range of medical and research environments, as they help maintain clean conditions in the smallest clinic to the largest hospital (Qian & Zheng 2018).
Division of Plastic and Reconstructive Surgery, Faculty of Medicine and Health Sciences, Stellenbosch University and Tygerberg Academic Hospital, Cape Town, South Africa
Corresponding author:
Sammy Al-Benna, Division of Plastic and Reconstructive Surgery, Faculty of Medicine and Health Sciences, Stellenbosch University and Tygerberg Academic Hospital, Francie van Zijl Drive, PO Box 241, Cape Town, 8000, South Africa.
Email: [email protected]
Journal of Perioperative Practice 2021, Vol. 31(1 & 2) 18–23
!The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1750458920949453 journals.sagepub.com/home/ppj
Understanding positive and negative pressure
rooms
Positive and negative pressure rooms are a common and essential part of controlling the spread of infectious diseases within hospital facilities (Luongo et al 2016). Air pressure in a room is influenced by whether air can enter and leave a room through gaps around windows, above and under doors, around lightfixtures and electrical outlets as well as through open doors and windows.
Positive pressure rooms maintain a higher pressure inside the treated area than that of the surrounding environment (Qian & Zheng 2018). This means air can leave the room without circulating back in. In this way, any airborne particle that originates in the room will be filtered out. Microbes, particles, and other potential contaminants in the surrounding environment will not enter the room. In medical settings, a positive pressure room (protective environment) allows staff to keep vulnerable patients safe from infections and disease (Judson & Muster 2019).
In contrast, a negative pressure room uses lower air pressure to allow outside air into the segregated environment (Qian & Zheng 2018). This traps and keeps potentially harmful particles within the negative pressure room by preventing internal air from leaving the space. Negative pressure rooms in medical facilities isolate patients with infectious conditions and protect people outside the room from exposure. A negative pressure room primarily keeps its air inside the room with controlled venting only, whereas a positive pressure room keeps unfiltered air from outside the room out of the room all together (Li et al 2007). Most homes have at least one negative pressure room: the bathroom. When a bathroom door is closed, if the bathroom has a quality working fan, unpleasant odours as well as moisture and humidity are vented out through the fan because the forced air ventilation creates a negative pressure room (Sepp€anen & Fisk 2004).
Definition of negative pressure rooms
A negative pressure room incorporates a ventilation system designed so that airflows from the corridor into the negative pressure room, ensuring that contaminated air cannot escape from the negative pressure room to other parts of the hospital area. Air naturally moves from areas of higher pressure to areas of lower pressure. When negative pressure exists, a continuous air current enters the room under the door, which prevents airborne particles generated in the room from escaping into the corridor. Typically, such rooms are used in the isolation wards of hospitals and medical centres, especially as part of the quarantine of contagious diseases such as chickenpox and tuberculosis. Negative pressure operating rooms are used when surgeries have to beperformed on patients who have communicable diseases.
Purpose of negative pressure rooms
A negative pressure room in a hospital is used to contain airborne contaminants within the room. Microbes (for example, viruses, bacteria, fungi, yeasts and moulds), pollens, gases, volatile organic compounds (VOCs), small particles and chemicals are part of a large list of airborne pathogens found in hospitals. Isolation rooms are negatively pressurised with respect to adjacent areas to prevent airborne contaminants from drifting to other areas and contaminating patients, staff and sterile equipment.
Rooms to negatively pressurise
Negative pressure rooms (airborne infection isolation rooms) are a common solution in infection control efforts (Chow et al 2006). Hospitals use them in patient rooms to ensure infectious microbes do not spread throughout the hospital via the heating, ventilation and air conditioning systems (Qian & Zheng 2018). Hospitals usually design the following areas as negative pressure environments:
• Public waiting areas, especially in the Emergency Department and Radiology
• Decontamination spaces
• Triage areas
• Bathrooms
• Airborne infection isolation rooms.
• Autopsy rooms
• Dark rooms
• Soiled laundry areas
• Most laboratory work areas
• Soiled workrooms or soiled holding rooms
• Soiled or decontamination rooms in sterile processing department
• Soiled linen sorting and storage
• Cleaners' closets.
It is worth noting how many of the areas listed affect not only patients, but also healthcare professionals and visitors in a hospital setting. Also of note is what is missingfrom the list. General patient rooms, nurseries, X-ray rooms, general examination rooms, and treatment rooms have no requirement of either negative or positive pressure.
Negative pressure isolation rooms
A negative pressure isolation room is commonly used for patients with communicable diseases, especially airborne infections. Many facilities are choosing to place potentially infected COVID-19 patients in isolation rooms when resources allow (Al-Benna 2020c). In order to ensure the safety of other patients, staff and visitors, it is
important that the isolation room contain negative air pressure. This will keep any microbes from entering the general airflow and infecting other healthcare
professionals, patients and visitors. A specially designed ventilation system installed in isolation rooms keeps contaminated air from escaping. In a properly
functioning negative pressure room, air is drawn into the room only through a 1cm gap under the door. Windows, lightfixtures and outlets are sealed so that air only exits the room through a filtered ventilation system.
Negative pressure isolation stations
In some hospital laboratories, healthcare professionals working with potentially hazardous materials may use a negative pressure station. Directly above the work space, a powerful ventilation andfiltration system will draw the air away and through a high-efficiency particulate air filter specifically designed to keep healthcare professionals, both in the room and in the building, safe from exposure to any hazardous fumes or airborne by-products.
Testing for negative pressure
A simple smoke test can ensure that a negative pressure room is working properly. To perform this test, close the door to the isolation room and stand in the corridor outside the door. Using a smoke tube, hold the bottom of the tube near the bottom of the door, 5cm away from the front of the door. Gently squeeze the bulb to release a stream of smoke. It is important that the smoke flow slowly from the tube so that the velocity of the smoke does not overpower the velocity of the air in the corridor. If the negative pressure room is functioning properly, the smoke will be drawn under the door and into the room. If the smoke remains stationary or is blown outward, negative pressure has not been established.
Positive pressure isolation rooms
Positive pressure rooms are usually used in scenarios that must continuallyfilter harmful contaminants out of the environment. The most common application is in rooms for patients who have compromised immune systems. For these individuals, it is important that no common pathogens from the outside, even those that are harmless to healthy people, enter the room. They are also used in situations that must continually maintain a specific type of atmosphere in a room, such as neonatal areas. Other uses of positive pressure rooms include in vitro fertilisation labs and operating theatres.
The air pressure in the room is greater than that outside of it, so it pushes potential infection agents or chemicals away from the patient. The most common application is in rooms for patients who have compromised immune systems. For these individuals, it is important that no common pathogens, even those that are harmless to
healthy people, enter the room. For positive pressure isolation rooms, an anteroom is recommended and incoming air isfiltered through both high-efficiency particulate air filters and ultraviolet germicidal
irradiation systems, which kill bacteria by exposing them to ultraviolet light.
Positive pressure can be used in rooms adjacent to a negative pressure room. This means that the air pressure inside a positive pressure room is greater than the pressure outside of it which is achieved by pumping infiltered, clean air. The purpose of positive pressure is to ensure that airborne pathogens do not contaminate the patient or supplies in that room. For example, positive pressure could be used in an operating room to protect the patient and sterile medical and surgical supplies. Positively pressured rooms are typically considered the cleanest rooms in the hospital.
Positive and negative pressure elements
Positive and negative pressure rooms both require a number of additional components to remain effective. A minimum of 12 air-flow changes each hour must be maintained in order to sustain the desired environment and, depending on the size and purpose of the room, more may be necessary (Lee et al 2018). The construction of positive and negative pressure rooms requires the use of specialised construction and climate control equipment, including:• Recirculation of air through high-efficiency particulate air filters to control the movement of airborne contaminants.
• Self-closing entryway with an adequate seal.
• Thoroughly sealedfloors, ceiling, walls, and windows.
• Fans and ductwork to move air in the desired directions.
• A monitoring system that allows users to adjust pres-sure when necessary.
• Intermediate environment between the pressure room and outside environment for deliveries, obser-vations, and protective gear storage.
Some medical facilities additionally incorporate ultraviolet radiation into the system to help maintain a sterile environment. Using ultraviolet light in a filtration system sterilizes particles and reduces microbes (such as SARS-CoV-2) in the quarantine space, helping to protect healthcare professionals who enter the room to provide care for the quarantined patient. Existing building heating, ventilation, and air-conditioningfilters may be used as a method of detection for airborne viruses. As integrated long-term bio-aerosol sampling devices, they may yield valuable information on the epidemiology and aerobiology of viruses in air that can inform the development of methods to prevent airborne transmission of viruses. One study demonstrated the
presence of influenza A virus, influenza B virus, and parainfluenza virus 1 in hospitalfilter (Goyal et al 2011).
Smoke test
Air pressure in a room is influenced by whether air can enter and leave a room through gaps around windows, above and under doors, around lightfixtures and electrical outlets as well as through open doors and windows. A simple smoke test can ensure that a negative pressure room is working properly. Gently squeeze the bulb to release a stream of smoke. The air pressure in the room is greater than that outside of it, so it pushes potential infection agents or chemicals away from the patient.
Conversion of a room from positive pressure to
negative pressure
Patient room airflow patterns and ventilation capacity should be considered when developing measures to prevent aerosol transmission of airborne infectious agents (Chow & Yang 2004). Although negative pressure rooms are ideal for aerosol-generating procedures such as intubation, most operating theatres are generally maintained at a positive pressure when compared with the surrounding areas (Al-Benna 2012). These operating theatres, including cardiac, cardiac catheterisation and orthopaedic, use positive ventilation systems and are not designed for infection isolation (Al-Benna 2012). Positive airflow ventilation can help disperse microbe laden aerosols (for example, SARS-CoV-2) in the procedure area. Conversion of a positive pressure room to a negative pressure room may be accomplished by building an anteroom at the site of patient entry into the operating room and sealing off additional access points to the room (Chow et al 2006). Airflow within the operating room also must be reversed (Chow et al 2006, Miller et al 2017). The anteroom allows for the passage of equipment and personnel without contaminating the surrounding environment. It should be large enough for the passage of a large hospital bed and permit adequate space for donning and doffing of PPE. In addition, it should have a self-closing door so that negative pressure in the room remains. The considerations for these changes are complex and require close collaboration with hospital epidemiology, facilities management, and industrial hygiene specialists (Ing et al 2020).
The feasibility of rapidly converting operating theatres into negative pressure rooms should be in hospital planning for COVID-19; portable high-efficiency particulate airfilters, for instance, can be set up to create negative pressure areas around the operating theatres (Chow et al 2006). A negative pressure anteroom can be established outside the operating theatre to be used for doffing and as an airlock, for use by staff who need to enter mid-case or pass supplies or specimens into and out of the procedure room (Chow
et al 2006). In addition, by adding two portable high-efficiency particulate airfilters and directing the high-efficiency particulate air-filtered exhaust into the operating theatre ventilation return columns, they were able to establish negative pressure airflow in the operating theatre (Chow et al 2006).
Intubation and extubation
As a rule, COVID-19 patients are best be accommodated in negative pressure isolation rooms on the ward. When these patients require operative procedures, a negative pressure theatre is considered to be more suitable than a positive pressure environment (Arora et al 2020, Ing et al 2020). In principle, a positive pressure operating theatre with adequate air changes could quickly eliminate the virus from the environment, and it has been shown that the risk of cross-contamination from airborne infection is low if operating theatre
professionals are adequately protected with appropriate personal protective equipment. However, a negative pressure operating theatre offers optimal protection to personnel working in adjacent areas.
Advance planning can help to ensure a safer intraoperative period when a COVID-19 patient is brought to the operating theatre suite (Al-Benna 2020d). Consideration should be given to intubating the patient prior to transport to the operating theatre suite, particularly if the patient originates in a respiratory isolation room with negative pressure airflow. Similar to intubation, extubation poses a risk of generating aerosolization of infectious airborne microbes, such as SARS-CoV-2 (Judson et al 2019). Extubation is performed when the intensive care/ anaesthetic team has determined the patient meets extubation criteria and has passed a spontaneous breathing trial (Arora et al 2020). Postoperative patients with COVID-19 should be transported intubated to a reverse airflow or negative pressure room in the post anaesthesia care unit or intensive care unit (Arora et al 2020, Chow et al 2006, Ing et al 2020). When a negative pressure room in the intensive care unit is not available for recovery, extubation may be performed in the operating theatre (Arora et al 2020, Chow et al 2006, Ing et al 2020). In this last circumstance, the patient remains in the operating theatre for 30 minutes after extubation to allow for turnover of air in the room prior to the doors opening for patient transport to the post anaesthesia care unit or intensive care unit (Arora et al 2020, Jensen et al 2005). A surgical mask can be placed over the patient's oxygenating face mask to reduce droplet spread during transport. Patients who are not intubated for the anaesthetic may befirst recovered in the operating room or transported under droplet precautions directly back to a negative pressure isolation room (Arora et al 2020).
Conclusion
The COVID-19 pandemic has resulted in extreme stresses and strains on the general running of hospitals. In the current COVID-19 pandemic, it is recommended that operating rooms be converted to negative-pressure rooms so that infectious transmission originating from within the room does not occur (Ing et al 2020). Efficiently installed positive and negative pressure rooms mean the difference between a healthy
environment for patients, healthcare professionals, and visitors and one compromised by infectious pathogens. Overall, although the risk of cross-contamination from airborne infection is low if staff are adequately protected with appropriate personal protective equipment, a negative pressure operating theatre can offer optimal protection to personnel working in adjacent areas. When rooms are not properly pressurised (negative or positive), airborne contaminants can escape putting the health of patients, healthcare professionals, and visitors at risk. This has never been more important than right now. No matter what systems are used, the need for properly functioning negative and positive pressurised rooms in the hospital is well documented to provide positive patient outcomes.
Declarations
Contributorship
The named author was actively involved in the planning, enactment and writing up of the study.
Disclosure
The author is not aware of any affiliations, memberships, funding, orfinancial holdings that might be perceived as affecting the objectivity of this study.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Competing Interests
None.
Acknowledgments None.
ORCID iD
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