Pressurization

Temporary negative pressure: How long is too long?

Negative pressure has become a hot button topic for all those in the front lines working with patients afflicted with the SARS-CoV-2 (COVID-19) virus. There is a significant amount of guidance from various organizations and regulatory agencies for temporary solutions along with explanations of why facilities should attempt to provide temporary negative pressure spaces. Specifically, the CDC recommends placing COVID-19 positive patients in a single patient room and keep the door closed. Additionally, the CDC recommends:

• Limiting transport and movement of the patient outside of the room to medically essential purposes.
• Housing patients in the same room for the duration of their stay.
• Whenever possible, perform procedures/tests in the patient’s room.
• Reserve Airborne Infection Isolation Rooms (AIIRs) for patients who will be undergoing aerosol-generating procedures.

Even with these recommendations, the risk of aerosol propagation of COVID-19 within the patient room increases. Temporary negative pressure rooms help mitigate the transmission of the aerosolized virus to adjacent spaces, containing contaminates and particles. How to achieve temporary negative pressure in a room will significantly depend on the design of the patient room and the ventilation system serving the patient room. The ASHE COVID-19 Negative Pressure webpage offers different negative pressure room concepts. 

Since these temporary negative pressure patient rooms and spaces are not a normally recognized health care space, there are not established requirements. As frontline clinical staff continue to be at the forefront of this battle with the virus, it is important that facilities leaders weigh the impacts of temporary negative pressure; what impact is it having on the building and how to continue to provide a safe environment while maintaining regulatory compliance if temporary negative pressure was implemented. 

The conundrum becomes, how long is temporary? The Merriam-Webster Dictionary defines temporary as “lasting for a limited time”. That does not give enough definition to use to assess how long these temporary negative pressure environments can be sustained. We can then look at, what other factors allow for temporary solutions to maintain active. One of those factors is emergency declarations, national, state and local declarations. If these declarations are in place, it allows waivers and loosened regulations to allow healthcare facilities to implement temporary solutions to respond to patient care needs, including negative pressure environments. 

What happens once the emergency declarations cease? If they cease at the national level but are maintained in the state or local level where the facility resides, that facility could continue to maintain temporary negative pressure with guidance from their local department of health and a well-documented plan. 

But what happens if all emergency declarations are lifted, what are the next steps to assess if facilities are compliant maintaining temporary negative pressure? The next course of action may be to work with the local authority having jurisdiction (AHJ) such as the department of health and fire marshal office to assess the needs of the individual facility and the continued use of temporary solutions for negative pressure environment. Consultation with the facility accrediting agency would also be advised to ensure compliance. 

In all these scenarios, continued documentation through the facility emergency operations plan will be essential to establish that the facility is still functioning outside of the normal operations and that the temporary negative pressure solutions are essential to ensuring safe patient care. If the facility returns to normal operations and discontinues the use of its emergency operation plan, it might prove challenging to continue to use temporary negative pressure since ASHRAE/ASHE 170 has no requirement for a pressure relationship for patient rooms. If the facility leadership continues to use a temporary negative pressure solution, an updated risk assessment with partnership of clinical, facilities, infection prevention, and senior leadership will be important to have well documented for the continued use of these temporary environments. 

Reassessment, risk assessments and continued documentation of the need and state of the facility to support temporary negative space will be important. Ultimately, it will be up to each individual facility to assess the continued use of temporary negative pressure measures implemented.

Patient Placement

Patient care spaces require careful consideration to ensure staff and patient safety. Space within a health care facility is designed to allow for routine situations and mitigate the spread of infection through engineering controls that address a number of different patient needs. The built environment is not designed to accommodate many patients with comparable needs, as is necessary with this pandemic. It is important to examine these changing facility needs with the assistance of qualified facilities professionals that can assess the facilities engineering controls and patient flow and help verify that your COVID-19 response will properly protect patients. We strongly recommend using a multidisciplinary approach, with professionals including but not limited to:

• Facility Manager
• Architect
• Professional Engineer
• Infection Preventionist

For patients with COVID-19 or other respiratory infections, evaluate need for hospitalization. If hospitalization is not medically necessary home care is preferred.

If hospitalization is necessary and ample airborne infection isolation rooms (AIIRs) are available:

• CDC doesn’t require placement in AIIRs, but consider using if resources allow.
• Limit transport and movement of the patient outside of the room to medically essential purposes.
• Patients should be housed in the same room for the duration of their stay.
• Whenever possible, perform procedures/tests in the patient’s room.
• Aerosolizing procedures should be done in an AIIR.

If hospitalization is necessary and AIIRs are limited, the CDC suggests placement in a single-person room with the door closed:

• Room should have a dedicated bathroom.
• Limit patient transport and patient transfers.
• AIIRs should be reserved for patients who will be undergoing aerosol-generating procedures.

To limit staff exposure and conserve PPE:

• Consider designating entire units for COVID-19 patients separate from units designated for persons under investigation (PUIs).
• Dedicated staff should be assigned to care for these patients.
• If multi-patient rooms used, all patients should be confirmed with the respiratory pathogen.
• Limit transport and movement of patients outside of room and unit to medically essential purposes.
• Patients should be housed in the same room for the duration of their stay.
• Whenever possible, perform procedures/tests in the patient’s room
  • AIIR’s should be reserved for patients who will be undergoing aerosol-generating procedures
• Terminal cleaning should occur after sufficient time has elapsed for enough air changes to remove potentially infectious particles, as indicated in the CDC table duplicated on this page. 

Air Changes Clearance Rates

Terminal cleaning should occur after sufficient time has elapsed for enough air changes to remove potentially infectious particles. For information on determining air changes per hour (ACH), see this instructional video. The facility should determine the desired efficiency for removal based on the CDC table duplicated below. The original table and references in the note may be found at the following link: https://www.cdc.gov/infectioncontrol/guidelines/environmental/appendix/air.html#tableb1erminal

* This table is revised from Table S3-1 in reference 4 and has been adapted from the formula for the rate of purging airborne contaminants presented in reference 1435.
+ Denotes frequently cited ACH for patient-care areas.

Surge Capacity

Individual Room Considerations
CDC does not require AIIR’s but the optimal situation is to create additional AIIR’s if resources allow

• AIIRs provide an extra layer of protection for staff and other patients:
  • For staff and other patients
  • COVID-19 patients may be coughing which aerosolizes the virus. While the virus is not itself airborne, some studies have estimated the time which the virus can be suspended within droplets in the air. 
    Source: The New England Journal of Medicine
  • AIIR Requirements:
    • Negative pressure relationship
    • Two outdoor ACH
    • Twelve total ACH
    • Exhausted directly to the outside
    • No air recirculation

If temporary creation of AIIR’s is not practical, the next consideration is creating negative pressure patient rooms. While these rooms may not comply with all of the requirements of an AIIR, negative pressure rooms may help control the virus within the room without spreading throughout the corridors. 

ASHE suggests consideration of the following methods for creating negative rooms:  

• HEPA to corridor
• HEPA to outside
• HEPA to return
• Multi-bed zone-within-zone room

See below for a detailed description of each type of room.

It is important to note that each negative pressure room will affect the air balance of the entire unit. Careful testing and balancing for all areas served by the air handling unit will be required.

Unit Conversion Considerations

Designate entire unit or units within the facility to COVID-19 patients

• CDC recommendations for these units:
  • Dedicated staff should be assigned to care for these patients
  • If multi-patient rooms used.
    • all patients should be confirmed with the respiratory
  • Limit transport and movement of the patient outside of room and unit to medically essential purposes.
  • Patients should be housed in the same room for the duration of their stay.
  • Whenever possible, perform procedures/tests in the patient’s room
    • Aerosol-generating procedures should be performed in AIIR’s.
  • Terminal cleaning should occur after sufficient time has elapsed for enough air changes to remove potentially infectious particles, as indicated in the CDC table duplicated on this page.  

Additional considerations for COVID-19 units

• If possible, create negative pressure environment within unit
  • Air handler should only serve area being dedicated to COVID-19 patients. This will increase pressure drop, so must verify T&B throughout unit and
    • need to verify impact of negative pressure to all rooms
  • Patient rooms should be made more negative than rest of unit
  • Rooms with required positive relationship should remain positive:
    • PE Rooms, Clean Linen, Clean Workroom/Holding
  • Limit access to the unit to only essential personnel
    • Create a Control Vestibule with Neg Air Machine at entrance
  • Verify negative pressure prior to placing unit in service and monitor negative pressure while in service
  • Do not place PUI’s in COVID-19 Units until positive test result confirmed
• Designate units specific to triage / PUI’s. It’s important that these types of spaces have negative pressure rooms. Comingling patients is not recommended.

It's important to consult the facilities manager and maybe a professional mechanical engineer before these systems are altered. To make large scale unit conversions you may need to modify the air handling unit in one of the following ways:

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