Health & Wellbeing

Nordic-style ventilation could reduce hospital-acquired infections

Nordic-style ventilation could reduce hospital-acquired infections
Two of the mannequins used in the study
Two of the mannequins used in the study
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Two of the mannequins used in the study
Two of the mannequins used in the study

In Nordic countries, where cold winters can keep people indoors, buildings often feature what are known as "displacement ventilation" systems. A Spanish study now suggests that such technology may also help keep patients from acquiring infections while in hospitals.

According to scientists at the University of Cordoba, over 90 percent of hospitals utilize the more commonly-seen "mixed ventilation" systems. This means that new air is introduced from vents placed near the ceiling, after which it gradually mixes with air already in the room. Eventually, most of the room's "old" air gets diluted by the fresh air.

By contrast, displacement ventilation systems introduce new air from vents located near the floor, closer to the patient. That fresh air then pushes the old air up to removal vents near the ceiling, with the warmth of that old air helping it to rise. Described as working like a piston, this system results in a quicker, more thorough turnover of air within a room.

In U Cordoba tests that incorporated life-size mannequins equipped with simulated human respiratory systems, it was found that use of displacement ventilation systems in hospital rooms could significantly reduce airborne pathogens.

Additionally, the technology may help hospitals save money on power bills. While mixed ventilation systems are required to be capable of refreshing the air in a room 12 times per hour in order to sufficiently remove pathogens, it is estimated that displacement systems would only need to do so nine times an hour for the same level of protection from infections.

A paper on the research was recently published in the journal PLOS ONE.

Source: University of Cordoba via EurekAlert

Nordic countries use radiators, so I guess they are saying radiators are better? Spent two weeks in the winter at a Swedish hospital, the air is not better.
How energy efficient is this proposed system?
Sebastian Brudell
No, Nordic countries uses radiators or under-floor tubes for heating. The modern venting systems (from the 80-ties =>) are called ERV or (more sophisticated ones) HVAC. At least ERV is required standard in all new buildings, including private homes. The exhaust air passes a heat exchange (or heat pump) before vented out to atmosphere, thus taking care of the heat energy. The incoming air is preheated and filtered before blown into the building. We recycle some 80-90% in EVR. For HVAC this figure is higher. Older hospitals don't have EVR or HVAC yet.
There are many commercially available systems, that constantly draw air in from outside the building, and it then passes through a heat exchanger, which sucks the air from inside the building and blows it to the outside, through the heat exchanger, so transferring the heat from the stale air to the fresh air. There is no mixing of air, so no possibility of pathogens being recirculated. The air is ducted, so that the ventilated internal air is released far from the intake. The intake and exhaust vents can be placed where it is most effective, and normally the exhaust is placed high, and the inlet low. It would also be possible to add a UV steriliser, and pollen filter, or similar to the inlet. It seems that this group are trying to re-invent the wheel.
Fresh air intake and HEPA filters accomplish this just fine. We even did it in the evac clinics in the war zone, in tents or borrowed buildings. Keeping the equipment running in that environment was a nightmare, but in temperate regions it's easy.
It is good to see, though, that attention is being paid to the relevant airflow and contamination factors.
Douglas Bennett Rogers
I actually have an ERV (RecoupAerator) which I bought in 1988. It is a window unit which I eventually installed in a duct system. Your main problem is sealing all of the other leaks so that the flow is entirely through the unit. The unit is in the basement and the air comes out of the unit into the basement. It enters the upstairs through two floor vents. It returns to the unit through the coat closet. It provides an air change about every five hours on the low 90 watt setting on about 15000 cubic feet.
I have a real simple version in my greenhouse 21,180 CF by pulling in the winter air thru 4" metal venting about 5' long. The bottom of the pipe is frosty but the top is warm. This must be done for heater performance so that the oxygen sensor doesn't shut the heater down.
Don Duncan
I have found forced air heat to be less comfortable/efficient than radiant. The best temp control is radiant floor heat/cooling.
amazed W1
Displacement ventilation is used in UK hospitals, both new constructions and refurbs, when it is desirable to isolate staff from a patient as far as possible and to collect and filter the air leaving the patient's immediate surroundings. That is both in acute infection wards and where a patient's treatment involves suppression of their immune systems. The airflow direction is upwards, and so in exactly the opposite direction to that used in manufacturing "clean rooms" where it is (conventionally) downwards. Doing this allows much reduced quantities of air to be used. But the efficiency with which the relative isolation occurs relies on the "plumes" of warm air generated by the human bodies to be strong enough to rise to a "pool" of warm air on the ceiling and not to be significantly influenced by temporary draughts from other sources, like people moving about. It is possible where really good isolation is required to supply relatively larger quantities of air through outlets surrounding the patient's bed, much more like an inverted "clean room."