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Negative room pressure is an isolation technique used in
hospital A hospital is a health care institution providing patient treatment with specialized health science and auxiliary healthcare staff and medical equipment. The best-known type of hospital is the general hospital, which typically has an emergen ...
s and medical centers to prevent cross-contamination from room to room.Negative Room Pressure to Prevent Cross-Contamination
Clean Air Solutions, Camil Farr, Retrieved 2010-03-10.
It includes a
ventilation Ventilation may refer to: * Ventilation (physiology), the movement of air between the environment and the lungs via inhalation and exhalation ** Mechanical ventilation, in medicine, using artificial methods to assist breathing *** Ventilator, a m ...
that generates
negative pressure Negative pressure may refer to: * Negative value of a pressure variable * Negative room pressure, a ventilation technique used to avoid contaminating outside areas * Negative pressure ventilator, also known as an iron lung * Negative-pressure wou ...
(pressure lower than of the surroundings) to allow air to flow into the isolation room but not escape from the room, as air will naturally flow from areas with higher pressure to areas with lower pressure, thereby preventing contaminated air from escaping the room. This technique is used to isolate patients with airborne
contagious disease A contagious disease is an infectious disease that is readily spread (that is, communicated) by transmission of a pathogen through contact (direct or indirect) with an infected person. A disease is often known to be contagious before medical ...
s such as:
influenza Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptom ...
(flu),
measles Measles is a highly contagious infectious disease caused by measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often greater than , cough, ...
,
chickenpox Chickenpox, also known as varicella, is a highly contagious disease caused by the initial infection with varicella zoster virus (VZV). The disease results in a characteristic skin rash that forms small, itchy blisters, which eventually scab ...
,
tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, ...
(TB),
severe acute respiratory syndrome Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1), the first identified strain of the SARS coronavirus species, ''sev ...
(SARS-CoV), Middle East respiratory syndrome (MERS-CoV), and
coronavirus disease 2019 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quickl ...
(COVID-19).


Mechanism

Negative pressure Negative pressure may refer to: * Negative value of a pressure variable * Negative room pressure, a ventilation technique used to avoid contaminating outside areas * Negative pressure ventilator, also known as an iron lung * Negative-pressure wou ...
is generated and maintained in a room by a ventilation system that continually attempts to move air out of the room. Replacement air is allowed into the room through a gap under the door (typically about one half-inch high). Except for this gap, the room is as airtight as possible, allowing little air in through cracks and gaps, such as those around windows, light fixtures and electrical outlets. Leakage from these sources can make it more difficult and less energy efficient to maintain room negative pressure. Because generally there are components of the exhausted air such as chemical contaminants, microorganisms, or radioactive isotopes that would be unacceptable to release into the surrounding outdoor environment, the air outlet must, at a minimum, be located such that it will not expose people or other occupied spaces. Commonly it is exhausted out of the roof of the building. However, in some cases, such as with highly infections microorganisms in biosafety level 4 rooms, the air must first be mechanically filtered or disinfected by ultraviolet irradiation or chemical means before being released to the surrounding outdoor environment. In the case of nuclear facilities, the air is monitored for the presence of radioactive isotopes and usually filtered before being exhausted through a tall exhaust duct to be released higher in the air away from occupied spaces.


Monitoring and guidelines

In 2003, the CDC published guidelines on infection control, which included recommendations regarding negative pressure isolation rooms. Still absent from the CDC are recommendations of acute negative pressure isolation room monitoring. This has led to hospitals developing their own policies, such as the Cleveland Clinic. Commonly used methods for acute monitoring include the smoke or tissue test and periodic (noncontinuous) or continuous electronic pressure monitoring.


Smoke/tissue test

This test uses smoke or tissue paper to assess room pressurization. A capsule of smoke or a tissue is placed near the bottom of the door, if the smoke or tissue is pulled under the door, the room is negatively pressurized. The advantages of this test are that it is cost efficient and easily performed by hospital staff. The disadvantages are that it is not a continuous test and that it does not measure magnitude. Without a measure for magnitude, isolation rooms may be under- or over-pressurized, even though the smoke/tissue test is positive. A 1994 CDC recommendation stated TB isolation rooms should be checked daily for negative pressure while being used for TB isolation. If these rooms are not being used for patients who have suspected or confirmed TB but potentially could be used for such patients, the negative pressure in the rooms should be checked monthly.


Continuous electronic pressure monitoring

This test uses an electronic device with a pressure port in the isolation room and an isolation port in the corridor to continuously monitor the pressure differential between the spaces. The advantages of this type of monitoring are that the test is continuous and an alarm will alert staff to undesirable pressure changes. The disadvantages of this monitoring are that pressure ports can become contaminated with particulates which can lead to inaccuracy and false alarms, the devices are expensive to purchase and install, and staff must be trained to use and calibrate these devices because the pressure differentials used to achieve the low negative pressure necessitate the use of very sensitive mechanical devices, electronic devices, or pressure gauges to ensure accurate measurements.


See also

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References

{{reflist Medical hygiene Infectious diseases Pressure Isolation (health care)