Pulmonology, Denver style

I have run across an unforeseen complication of going to medical school in Denver. We're in the middle of the pulmonology section right now, and it turns out that altitude has an effect on lung function. Who'd have thunk?

Up here in the mile-high city, the atmospheric pressure is appreciably lower (thinner air) than the atmospheric pressure at sea level. Since this has real-world clinical relevance, especially during our third and fourth year clinical rotations, we have to know - and will be tested on - physiological values based on Denver's altitude.


PB = Barometric pressure (Torr)
PiO2 = Partial pressure of oxygen in inspired air (Torr)
PaO2 = Partial pressure of oxygen in arterial blood (mm Hg)
PaCO2 = Partial pressure of CO2 in arterial blood (mm Hg)
SaO2 = Saturation of oxygen in arterial blood (%)
CaO2 = Oxygen concentration in arterial blood (mL O2 / 100 mL blood)
CaCO2 = CO2 concentration arterial blood (mL CO2 / 100 mL blood)
[HCO3-] = Bicarbonate concentration in arterial blood (mM)

To be fair, every medical student in America has to learn (hopefully) a set of equations that relate all of these terms with each other. That means a medical student in Boston or New York or Los Angeles should be able to derive these values for a patient at any given altitude. The catch is that, here in Denver, we have to memorize two sets of values. It's worth noting that most USMLE Step 1 board questions will likely specify that the patient is at sea level.