PF Ratio, PAO2, P-Little AO2 Divided by FIO2

A to A gradient, it's like the millimeter in mercury difference. So you have X amount in your alveoli. It's going down as concentration gradient into the, into the PA, P-little AO2. That's pretty much making it through. And then your P, your A to A ratio, that's going to be looking at the percent of oxygen. Those will really start to show up when your PAO2 gets high and it can show you maybe how much of that LV-yield or hypoventilation is contributing to your patient being hypoxemic. The oxyhemoglobin desaturation curve was a nice little puzzle piece in between those two numbers