The climate scientists were all wrong when projecting future increases in the Earth’s temperature… it is happening much faster than they thought it would. These hotter temperatures turn out to have a big impact on hospital’s operating rooms. June 2016 was the 14th straight month that broke the monthly record for the hottest of those months on Earth ever recorded by NOAA. The average land temperature on Earth during June 2016 was 2.23° F higher than the 20th century average for June. In Central Ohio, not only are the temperatures higher this summer, but so is the humidity.

No matter what the outside weather, the inside of an operating room has to be in constant climate of 68-74° F and 30-60% humidity with up to 25 room changes of air per hour (that is a lot more room changes than your home central air conditioner has to do). Air handler units built into hospitals in the northern United States in the 1960’s and 1970’s were not built for the high temperatures and humidity that we are now experiencing. To understand why this is a problem, I had to take a crash course in HVAC systems from our director of facilities.

For air to get from the outside atmosphere into the operating room, it has to go through several steps. First, air is drawn into the HVAC system from intake vents. The air then passes through a heating coil (turned on in the winter) and a cooling coil (turned on in the summer). The cooling coil circulates a cooled liquid, in our hospital’s case, it is cooled water that comes from a refrigeration unit in our boiler room. The air then goes through a filter so that it is 99.997% pure. Next come additional heating and cooling coils to get the air to the proper temperature for any given location in the hospital.

If the room is too hot, then surgeons with gowns on and patients with drapes on can get overheated. Humidity comes into play also because if the humidity gets high, then the air will seem several degrees hotter even if the temperature doesn’t change (this is the difference between the actual temperature and the “heat index”).

In order to maintain constant temperature and humidity, it can require a lot of frequent adjustment in air handler controls. Recently, the temperatures and humidity in Columbus were really off the charts for long periods of time and we started seeing our operating rooms’ temperature and humidity rise excessively.

So here is what we had to do. The first cooling coils were set to 42° F. The air doesn’t get that cold but this does maximally reduce the humidity (i.e., dries the air out). The air gets down to about 56° F. Although that is plenty cold for operating room air, the air was still too humid so we next heat the air up to 68° F with the secondary heating coils in order to further reduce the humidity. So, in order to get it right, we had to supercool the air then warm it back up to get the humidity down.

This works OK for now but if  we continue to have heat record breaking months in the next few years, then hospitals in areas of the country where constant high heat and high humidity were not previously a problem are going to have to invest in expensive new HVAC systems in order to maintain the tightly controlled climates that our operating rooms require.

August 5, 2016

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