Analysis of Wet Bulb Globe Temperatures with Regard to Patient Treatment and Management

This week, while experimentation and surgery go on, I am analyzing data regarding extreme temperatures.

Significance: 

While this is human data and not data we collect experimentally from rats, this is a retrospective clinical study that enables us to further understand patient outcomes when a patient has sustained and endured an injury in an extreme climate. While many cases occur in severe heat due to geographical reasons (all cases occur in Arizona or neighboring regions), there are many that occur in severe cold.

A clarification: When we say "extreme temperature," just because the temperature as indicated by the local weather station says "100 degrees Fahrenheit," does not necessarily make this temperature extreme (even though it undeniably is). What "extreme temperature" means in this context is the temperature as a person feels is, accounting for position of the sun (to determine heat stress accurately), solar irradiation, as well as what type of area a person is in. This type of temperature is called wet bulb globe temperature.

I had finished all 260 case files last year; however, the data was unusual. In the summer, we were seeing low wet bulb globe temperatures. After a lot of backtracking, we determined that we calculated wet bulb temperature, rather than wet bulb globe temperature. The difference being: wet bulb temperature is the temperature that a sample of air would have if it were cooled to 100% relative humidity (saturation) by the evaporation of water into it, with the latent heat being supplied by the sample. For example, this temperature implies 100% relative humidity, while wet bulb globe temperature takes the true humidity into account. In Arizona, our summers are hot and dry; therefore, the wet bulb temperature is lower in the summer than the wet bulb globe temperature. 

Now understanding this calculation error, I am starting from scratch, along with a few modifications in calculations to accommodate for specific locations were patients sustained injuries.

What we're looking at:

• ID Number: In the trauma registry, patient cases are listed under ID numbers. These ID numbers list patient data, while allowing the patient to maintain confidentiality.
• GPS Coordinates: This enables us to look at where a patient was located and what type of region (rural or urban) a patient sustained injury. From these GPS coordinates, I locate the three closest weather stations and record their data for the specific day, time, and year a patient was injured. We look at the elevation of the weather station to determine atmospheric pressure (see below) and the distance of the place of injury from the weather station to accurately weight wet bulb globe temperature.
• Air temperature (in Celsius)
• Relative Humidity: The amount of moisture in the air compared to what the air can "hold" at that temperature.
• Solar Irradiation: The power per unit area produced by the Sun in the form of electromagnetic radiation.
• Atmospheric Pressure: The force per unit area exerted against a surface by the weight of the air above that surface.

This clinical study is very unique and it is a privilege to be a part of it, as it has huge implications for patient treatment and management when patients endure extreme temperatures. Meaning, how should we address a patient's treatment differently when we know that he or she has been exposed to cold weather, rather than hot and dry temperature? This is essentially what we hope to determine from this retrospective study.