The PAO2 to FiO2 Ratio

The PF ratio is comparing how much oxygen is going in versus how much is actually making it into the blood. It's a nice number to look at because if somebody's got a bunch of boogers in their lungs or they got pneumonia, a significant pulmonary shunting, you're not all going to make it into their blood. But when you are looking at that, one of the faults of the PF ratio is that one, it's very hard to communicate from one ventilator strategy to another. And so then you're like defining the disease process by the person's ventilator knowledge that's titrating the knobs and turning up the eye time and playing with the peep