The P/F ratio is a quick calculation you can do that will give you some clues as to whether your patient is A-OK pulmonary wise or heading toward ALI (acute lung injury) or ARDS (acute respiratory distress syndrome).
First, find your PaO2 from your blood gas and the FIO2 on your vent. For this example, let’s say your PaO2 is 83 and your vent is set at 45% FIO2.
Next, convert your FIO2 into a decimal…in this case it is 0.45
Then, just simply divide your PaO2 by the FIO2…it will look like this: 83/0.45 = 184.
A P/F ratio less than 300 is suggestive of ALI, while a P/F ratio less than 200 is suggestive of ARDS, which is the most severe form of ALI and super scary. Of course, you never just go by numbers alone…always look at your patient and take in the whole picture (suddenness of onset, chest x-ray, etc….).
In another post, we’ll look at the alveolar-arterial gradient and then you’ll be feeling super smart as you chat with those awesome respiratory therapists and make recommendations to the MD. You got this!
Be sure that you never miss a post…sign up for the email list in the top right sidebar!