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Air quality in the Operating Room

Air quality in the Operating Room

If you are in the position to have elective surgery, you probably assume that the hospital does its best to mitigate infections by maintaining a sterile environment and using sterile procedures.  The Operating Room (OR) is where patients are at their most vulnerable because hospital-acquired infections (HAIs) can easily happen when the skin barrier is broken, resulting in a Surgical Site Infection (SSI).  Therefore, air quality is very important for patients’ protection, and there are a number of factors that govern the quality of the air.  In the U.S., OR air quality is regulated by three organizations: the American National Standards Institute (ANSI); the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE); and the American Society for Healthcare Engineering (AHSE). Operating rooms require positive pressure, a minimum of 20 air changes per hour (ACH), with a minimum of four outdoor changes per hour. The standard specifies a minimum effective reporting value for air filter efficiency (MERV 16) but does not recommend a type of air delivery system. (Operating Room Sterilization: A Complete Guide to Air Quality)  Here are some details about these requirements:

  • Positive or negative pressure: Traditionally, hospitals make operating rooms positive pressure in order to keep contaminants from the rest of the hospital from infecting the patient on the operating table.  According to ASHRAE 170, operating rooms require positive pressurization of at least +0.01 in.w.g.  However, as operations are sometimes necessary on patients who may have contagious diseases like MERS or SARS CoV-2, hospitals are beginning to rethink whether they want to put the rest of the ward at risk of spreading a microbe from a positive pressure OR room. Discussions are underway regarding alternatives such as a positively pressured OR with negatively pressured ante/setup rooms. Another possibility is to have a negatively pressured OR with positively pressured ante/setup rooms.  (Rethinking air pressure in operating rooms could save lives)

  • The air change rate is a key factor influencing the concentration of microbe-carrying particles (MCPs). The higher exposure risks of surgical incision in the surgical microenvironment may be mitigated with increasing air changes per hour (ACH). (The impact of air change rate on the air quality of surgical microenvironment in an operating room with mixing ventilation)  

  • A key design requirement within ASHRAE 170 for operating rooms is the primary supply diffuser array. The airflow in the primary diffuser array should be unidirectional and downward, with an average velocity of 25 to 35 cfm per sq. ft.  This is recommended with the sole intent of creating a large sterile zone around the patient and medical staff. The standard dictates that the coverage area of the primary supply diffuser array should include the surgical table and extend a minimum of 12 in. beyond the footprint of the surgical table on each side and that no more than 30% of this area may be used for nondiffuser uses (like lighting, surgical gasses, electrical outlets, televisions, etc). This recommendation ensures that enough clean, filtered air is dispensed above the patient while accommodating the complex medical equipment present in today’s modern operating rooms. (How is ASHRAE Standard 170 Applied to Hospital Operating Rooms?)

Although not it’s not mandated, it’s also a good idea to have restricted access to the OR during surgical procedures.  The number of door openings are related to the number of colony-forming units (CFU) in the OR.  According to this study, increased number of door openings and surgery duration increased CFU counts in the OR, but the relationship between these variables was only observed outside the Laminar Air Flow.(LAF). Within LAF conditions, only the number of staff was associated with higher CFU. 

There have been several key developments in systems that promote ultra-clean operating rooms.  Laminar Air Flow (LAF) systems were developed by Sir John Charnley in the 1960s for use during joint replacement implantations.  They are useful for maintaining sterile conditions in the center of the operating room (under the diffusers) because they produce a continuous flow of microorganism-free air, which improves air quality by reducing infectious microbes. However, a 2023 meta-analysis agreed with multiple studies that have found it ineffective for reducing SSIs, and even possibly increasing the likelihood of SSIs, during orthopedic procedures.  (Laminar airflow ventilation systems in orthopaedic operating room do not prevent surgical site infections: a systematic review and meta-analysis)  In addition, air outside of the sterile field (that which is supplied by the LAF system) is often called the “dirty donut” because it is not effectively sterilized by the LAF; air in the dirty donut can be up to 100 times more contaminated than the center.  There are several solutions to improving the air in the dirty donut; Aerobiotix has developed a mobile unit called Illuvia that can reduce the contaminants.  

Source: Cleaning up the Dirty Donut

There is no standard for LAF design in the US.  In addition to the filters employed, different sterilization devices can be employed within or outside the LAF cabinet to increase deactivation of pathogens.  According to Steris, a major design/manufacture/installation firm for OR suites, the following technologies are improving LAF cabinets: 

  • UV light: Use of mobile and ceiling mounted UV light systems is restricted to when patients and staff use full personal protective equipment.  This type of light is also limited to line-of-sight, meaning that disinfection is obstructed by ceiling mounted fixtures and other equipment.  UV light may also embrittle certain materials and fixtures.  Therefore, in-duct UV sterilizers are preferred.

  • In-duct hydroxyl generator systems ultraviolet energy to produce reactive oxygen species known as hydroxyls. Airborne hydroxyls are ideal sanitizing agents which reduce pathogens and neutralize volatile organic compounds (VOC) and a broad range of chemicals. Atmospheric hydroxyls are natural-occurring molecules produced by the action of the sun’s ultraviolet energy on oxygen and water in our atmosphere. The hydroxyls are a natural oxidant and safe for patients and staff to be present during treatment without additional PPE. The system can run continuously and year-round, providing the potential for maximum surgical uptime. An added benefit is that hydroxyls help mitigate odors caused by surgical smoke and cauterized tissues.

According to this 2018 paper, it may be wise to adopt some standards of cleanrooms in ORs.  One such principle is maximizing the use of ceiling space to make the ceiling one large diffuser.  The reason for this is that every gap in airflow delivery (for instance, around a light connection) causes a low pressure area into which airflow is directed, producing turbulence.  Therefore, the operating room would look more like this: 

Source: How is ASHRAE Standard 170 Applied to Hospital Operating Rooms?

LAF is also described as Uni-Directional Air Flow (UDAF), but UDAF may not always be laminar.   Here’s the difference: UDAF describes the direction of flow, however the velocity must be below 90 feet per minute in order to be described as laminar (non-turbulent).  It’s easy to see that the periphery (outside the Ultra Clean Ventilation area in the center) has a lot of turbulent air flow.  Although the large lights over the operating table do produce some turbulence, it is not visualized here.

Source: Air Quality in the Periphery of Operating Rooms during Surgery

Previous LAF systems utilized fans to force air down.  A new type of LAF system called Opragon was developed by the Swedish firm AvidCare, and the system uses Temperature-controlled AirFlow (TcAF).  The technology behind TcAF is based on the ventilation system pumping out slightly cooled air into a zone around the operating table. By taking advantage of the fundamental laws of nature, TcAF breaks the convection currents in an effective and energy-efficient manner. Since cool air is denser than the surrounding warmer air, it drops towards the floor. The air speed is dictated by the temperature difference in the room.  a temperature difference (ΔT value) of -1.5 to -3°C is required between the ultra-clean air and the ambient room air at the operating table to guarantee a fall speed of about 0.25 m/s at the level of the operating table. The technology continually checks to ensure that the ultra-clean air maintains a constant under-temperature of 1.5–3°C regardless of the temperature of the ambient room air. (Temperature-controlled AirFlow)

Air curtain systems like Mediclean emit an air curtain around the perimeter of the sterile area.  The Mediclean system uses Continuous Particle Monitoring (CPM) to measure airborne particles in real-time and uses simple visual alarms. When particles are detected, Mediclean® CPM systems automatically increase the airflow from the UCV to quickly flush the contamination away from the safety-critical area, protecting both patients and surgical staff.

Other innovations include:

  • Surgicube, which is positioned just above the operating table, emits sterile air for minor surgeries.

  • Surgibox, a portable sterile surgical field with self-supporting battery and filter system

  • Air Barrier System, which is a portable diffuser to bathe the surgical site in ultra-clean air 

  • A novel upward-flow design to ventilate using natural stack effect, which is less complex requiring fewer scarce components, lower maintenance commitments, lower energy requirements and operating costs.

And, it’s likely that even more innovations are in the pipeline.  We thought it would be helpful to let you know that even the air in operating rooms is important for the operation’s success and your healing, so you might want to check into it if you need to have surgery!

The Consequences of Flushing the Toilet with the Lid Open

The Consequences of Flushing the Toilet with the Lid Open

Spoiler alert: the consequences are not pretty.  This calming (Australian?) voice and wonderful orchestral soundtrack in this December 2022 video belie the serious and gross subject: how much germs and fecal matter shoot out of a toilet when you flush it.  The University of Colorado Boulder researchers who produced the video found that airborne particles ejected from the toilet traveled at speeds of up to 6.6 feet per second (that’s a very fast walk at 4.5 miles per hour) and reached 4.9 feet above the toilet and smaller particles measuring less than 5 microns hung in the air for more than a minute. 

It’s not a new subject (the subject was first revealed in a 1975 study, and another 2013 study warned about the toilet plume) but the video using UV light brings it to the forefront of our minds and hopefully, engages us in healthier bathroom habits such as closing the lid and sanitizing surfaces more frequently in our own private bathrooms. 

So what should we do?

Ever since Febreeze informed us that odor can be caused by bacteria, bathroom odors are particularly noxious, as we know that the substances that cause it definitely have dangerous bacteria.   There are different ways of removing/preventing bathroom odor (and thus bacteria).  In light of the knowledge of toilet plumes, toilet sprays like PooPourri, although emitting a pleasant odor, seem to be one of the least effective because while spraying on the bowl creates a scented vapor, it does not prevent the emission of bacteria and particulates into the atmosphere.  Other products on the market that have been invented to remove toilet odors at the source, using hardware to pull vapors from the bowl area.  These include:

  • Potty Sniffer Toilet Odor Ventilation System ($271 and up): fan directs air from bowl into a nearby vent.  This is the preferred place to direct these gasses.  However, installation is a bit more complicated as connecting to a vent may require to drill into drywall or cabinets, which needs work to conceal. 
  • JonEvac  Toilet Seat Ventilation System ($300): Replaces your toilet seat with a special seat that has ventilation channels on the underside.  Fan needs to be plugged into a regular wall outlet and activated carbon filter ($80) needs to be replaced every 1-2 years.
  • Splashblocker was invented primarily for hospital settings.  It is a portable “shield” to protect healthcare workers from disease and hazardous drugs (like chemotherapy) that are excreted in patients’ waste, which are aerosolized whenever the toilet is flushed. Previous to this invention, caregivers often placed plastic-backed absorbent pads (such as are used in keeping beds dry from incontinence) over the toilet before flushing, but the cost of these adds up and can easily be sucked down the toilet, creating big plumbing issues.
  • According to this 2020 study, a redesigned toilet seat that can spray a “liquid curtain” of water or sanitizing solution over the bowl when you flush can effectively impede upward movement of particulates, and only 1% of (bacteria/virus-laden) aerosols enter the air above the toilet seat.

The forceful flushing of vacuum-assisted flush toilets, which are commonly used in public restrooms (and all airplanes), actually do a great job of eliminating the toilet plume.  This video uses blacklight just like the study at the beginning of the article, and the difference between regular toilets and this vacuum system seem to be huge.  There were no particles coming out of the vacuum-assisted toilet, but many coming out of the regular flush toilet.  Vacuum-assist toilets still use water to help flush, but nowhere near the amount of regular gravity systems.   This fact comes from the AcornVac website (a manufacturer/supplier of vacuum toilet systems): “a 500 person commercial office building that is serviced by a single vacuum center and 1/2 gallon per flush vacuum toilets will save over 265,000 gallons per year, compared to conventional low flush toilets.”  Water savings aside, I think that the absence of a toilet plume when using a vacuum toilet is their greatest benefit, and it makes me feel a whole lot better about using the bathroom on airplanes!

What happens when the lid is lowered?

Since vacuum-assist toilets and shields are not commonly installed in residences, most people have only a lid to guard against the toilet plume.  What happens when you put the lid down and flush?  Obviously, there are particulates and germs landing on the inside of the lid.  (This is an area that gets skipped over when cleaning, I’m sure!)  The rest of the particulates exit through the spaces between the toilet, seat and lid.  Here are the good and bad results of flushing with the lid down, assessed by researchers at University College Cork:

  • Reduced the number of both visible and smaller droplets during and after flushing by 30-60%
  • increased the diameter and concentration of the bacteria in these droplets.
  • airborne microdroplets were detected for 16 minutes after flushing the toilet with the lid down, 11 minutes longer than when the toilet was flushed with the lid up. 
  • Another study concluded that lowering the lid before flushing “reduced 48% of total number concentration, 76% of total surface area concentration, and 66% of total mass concentration, respectively.”

Using the lid when flushing definitely helps, however some aerosols are still shooting out, and hanging around even longer.  What are the other things we can do to protect from THE PLUME?

  1. If you are in a public place and concerned about transmission of disease, put on an appropriate mask before going into the restroom–at least the aerosols should be filtered out of your air, and germs will not land on your nose or mouth.  As always, wash your hands thoroughly, and don’t touch your mask or face!
  2. If you’re at home, it goes without saying to clean regularly.  
    1. Use a non-toxic disinfectant on all surfaces in the bathroom.  Check out our article on the differences and methods of cleaning, sanitizing and disinfecting. 
    2. Change hand towels frequently, at least twice per week.  For towels and clothing that have been exposed to toilet plume, you can add Borax to your laundry, or pre-soak with it, as it turns into hydrogen peroxide when hot water is added to it.  It’s also generally safe for colored clothes.
    3. Use a HypoAir bipolar ionizer like Germ Defender or Upgraded Air Angel Mobile to sanitize the air and surfaces in your bathroom 24/7!
    4. Leaving your toothbrush in an open place on the bathroom counter sounds icky (for obvious reasons), but stashing it away in a plastic container or drawer is not advised either.  According to a meta-study published in 2012,  toothbrushes stored in aerated conditions had a lower number of bacteria than those stored in plastic and bacterial growth on the toothbrush increased 70% in a moist, covered environment.  What should we do with our toothbrushes?  Sanitize your toothbrush regularly by soaking it in hydrogen peroxide, Listerine, or using an approved UV sanitization device (but not in the microwave). (Is your toothbrush covered in poop? Here's how to thoroughly clean it)
    5. It’s best to switch on your bathroom exhaust fan before every flush, and leave it running for at least 15-20 minutes afterwards.  If your exhaust fan does not seem to remove odor very quickly, then you know it’s not removing the “toilet plume” aerosols.  It may be under-sized, or just old and inefficient.  Because the bathroom exhaust fan is also a very important appliance to remove humidity (and thus prevent mold), check out our article on how to check its size and where it should be vented!

Sorry, I know after seeing that first video, I couldn’t “un-see” it, but I’m grateful that non-toxic cleaners and laundry methods have been invented.  We just need to somehow lower the cost of vacuum-assisted toilets, and bathrooms will get a lot cleaner!