O2 supplement

I wonder if what she is getting at is, what is the cause of the decreased tissue perfusion? I don't have supplemental O2, but I am perfusing just fine. What is the difference between me and them. What role does O2 play for this specific patient and their comorbidities?

There is a difference between oxygenation and perfusion. Think of perfusion as the body's ability to move blood from point A to point B. It has to do vessel patency or flow and the heart's ability to pump. Blood vessels constrict to improve perfusion. Raising blood pressure helps with perfusion. The pumping of the heart is the actual perfusion mechanism, regardless of the oxygen levels. O2 supplementation increases oxygenation....the amount of oxygen in the blood, but it doesn't increase the amount of blood perfusion. If a drop of blood has an oxygen saturation of 50% or 100%, it won't matter if the vessel is blocked, occluded, or spasming. If you give someone oxygen who has heart failure, that isn't going to help with perfusion, but you can put them on a medication that causes the heart to squeeze better which delivers the oxygen. Another example if CPR. You give oxygen to raise their o2 levels, but you do chest compressions to perfuse the organs. You can't prevent hypoxemia unless the blood is openly moving. Perfusion = circulation. Make sense?

As hodgieRN has said, circulation = perfusion. Oxygenation is something different, and that part is addressed with the oxygen that you give to supplement the patient's need. In other words, a patient could have excellent perfusion, and still be hypoxic at the tissue level because something is wrong with the body's ability to exchange gases, either in the lungs, or the capillary beds. It's also possible for a patient's blood to be very well oxygenated, but again, results in hypoxia at the tissues because of a circulatory problem (perfusion). In order to maintain good oxygenation at the tissues, oxygenation (gas exchange) and circulation (perfusion) have to work well together because a failure on either and will result in tissue hypoxia. As we all know, that is a bad thing.

There is a saying: "air goes in and out, blood goes round and round, any deviation from that is bad." The only thing missing from that saying, is that gas exchange must occur at two places, the alveolar capillary beds, and the tissue capillary bed. Where the thinking comes into play, is how do we correct a deficiency that results in tissue hypoxia. Start with the basics and go from there!

Remember that, simplistically, breathing is ventilation, circulation is perfusion.

The idea of oxygen supplementation is to put more oxygen on the leetle red cells. Whether those leetle red cells get delivered to the cells that need the oxygen they carry is a matter of perfusion, but the oxygen doesn't cause the perfusion.