Getting the Right Medical Room Pressure

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Getting the Right Medical Room Pressure

With airborne infectious diseases that can easily spread from one person to another, such as the COVID-19 virus, isolation is critical. In a hospital or clinic, an isolation room needs negative pressure to have airflow into the room and avoid pathogens, or germs, from escaping. In addition to viruses, other undesirable contaminants to keep away from the rest of the population and sterile equipment in a hospital include bacteria, fungi, yeasts, molds, pollens, gases, volatile organic compounds (VOCs), small particles and chemicals.

The airflow to create and maintain the negative pressure (vacuum) in the room requires a consistent pressure differential of about 0.01 inch water gauge (in. w.g.) or 2.5 Pascals (Pa).

According to the Facility Guidelines Institute’s (FGI’s) most recent 2018 FGI Guidelines ANSI/ASHRAE/ASHE Standard 170-2017, other rooms that should be negatively pressurized include:

  • Emergency Department Public Waiting Areas
  • Emergency Department Decontamination
  • Radiology Waiting Rooms
  • Triage
  • Bathrooms
  • Airborne Infection Isolation (AII) Rooms
  • Most Laboratory Work Areas
  • Autopsy Rooms
  • Soiled Workrooms or Soiled Holding Rooms
  • Soiled or Decontamination Rooms in Sterile Processing Department
  • Soiled Linen Sorting and Storage
  • Janitors’ Closets

In contrast, protecting the patient and sterile medical and surgical supplies in an operating room requires positive pressure to keep undesirable contaminants outside. The positive pressure room is achieved by pumping in filtered, clean air.

Isolation (Low) vs. operating room (High) pressure

Isolation (Low) vs. operating room (High) pressure.
Source: Minnesota Department of Health

In fact, some portable, headgear-mounted air purifying respirator systems use positive pressure to protect the wearer.

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The Pressure for Ventilators

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

The Pressure for Ventilators

In addition to the pressure to get more ventilators, pressure is an integral part of a ventilator’s operation. Breathing involves inspiratory (inhaling) pressure and expiratory (exhaling) pressure and a ventilator has to take the user’s values into account. Peak Inspiratory Pressure or PIP is the maximum pressure inside the lungs during each inhaled breath and the normal range is 25-30 cm H2O. Positive End Expiratory Pressure or PEEP is the amount of pressure left inside the lungs at the end of a breath to keep the alveoli, tiny air sacs of the lungs, open. The normal range is 3-5 cm H2O.

The pressure inside a patient’s lungs depends on the compliance of their lungs. While the suggested range of pressures during ventilation is 20-35 cm H2O with an absolute maximum of 40 cm H2O, someone with damaged lungs may need a higher pressure.

 

Airway pressure and flow waveforms during constant flow volume control ventilation show PEEP and PIP

Airway pressure and flow waveforms during constant flow volume control ventilation show PEEP and PIP.
Source: http://rc.rcjournal.com/content/59/11/1773/tab-figures-data

With pressures below 50 cm H2O (19.7 in H2O or 4,903 Pa) for dynamic measurements, a pressure sensor designed specifically for these low pressures, such as All Sensors’ DLC, DLLR, and others, provide the required accuracy.

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Pressure and a Properly Flushing Toilet

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Pressure and a Properly Flushing Toilet

Replacing a toilet fill valve can solve some of the common toilet problems including excessive noise. With the proper adjustments, an adjustable universal fill valve works on a variety of toilet models. For example, one manufacturer’s fill valve has a gross height adjustment that extends the unit from 9 to 14 inches and a fine water level adjusting screw to set the level of water in the tank. While adjusting the water level lower to be more conservative and save water for each flush may seem like a good idea, the difference in as little as ½ to 1-inch of water height in the tank can mean the difference between the toilet flushing properly or requiring a second flush.

A ½-inch of water is only 0.018 psi, 124.5 Pa or 0.0368 millimeter of mercury (mm Hg). Measuring this low pressure is often a problem for pressure sensors but the All Sensors MLDX Series has 5 and 10 inH2O ratings to measure the low pressures found in many medical and heating, ventilation, and air conditioning (HVAC) flow applications, as well as other ratings up to 100 psi. Fortunately, for toilet adjustments, it is simply a matter of observing the situation to make the proper adjustments and no pressure sensing is involved.

Fluidmaster Toilet Fill Valve

Image courtesy of Fluidmaster

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Pressure and Sneezing

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Pressure and Sneezing

Don’t cover a cough or sneeze with your hand — cough or sneeze into your upper sleeve. It just makes sense, since the hand will be used to touch something including another person’s hand and spread any germs in the cough or sneeze unless the hands are washed immediately.

According to one author, “a sneeze is an expulsion of air from the lungs through the nose and mouth.” Without any covering at all, a sneeze can project droplets at a speed of up to 100 miles per hour for a distance of as much as 26 feet (8 meters) due to the pressure in the windpipe. While the sneeze only last for as long as 150 milliseconds, the droplets can stay suspended in the air for up to 10 minutes.

In either case, covered or uncovered,  the pressure developed during the sneeze can be around 1 psi (51.7 mmHg) in the windpipe. Another author measured the pressure developed in the mouth/pharynx during a sneeze as about 135 mmHg (2.6 psi) reached in about 0.1s. In contrast, a person exhaling hard during strenuous activity has a windpipe pressure of about 0.03 psi (1.55 mmHg). If you try to hold the sneeze back, the pressure inside the respiratory system can increase to a level of about 5 to 24 times the sneeze pressure. In rare instances, this pressure level can have detrimental side effects including:

  • Ruptured eardrum
  • Middle ear infection
  • Damaged blood vessels in the eyes, nose, or eardrums
  • Diaphragm injury
  • Aneurysm
  • Throat damage
  • Broken ribs

WikiHow Stop a Sneeze

Image source: https://www.wikihow.com/Stop-a-Sneeze

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