Kluver_Bucy said:
What would be the effect of giving oxygen to a patient with ARDS, Pulmonary Shunt, Emphysema, Fibrosis, and Pleural Effusion. Which conditions would increase oxygen saturation in a patient?
Thanks for your help 😍
You should categorize these.
1. Diffusion defect: CHF, interstitial fibrosis, pulm edema, etc. In these people, there is increased thicknes btwn alveoli and capillaries. However, giving them O2 increases the gradient, and therefore, they respond to increase in O2. A-a gradient decreases as a result.
2. Pulm shunt: atelectasis (ARDS), congenital R-->L shunts. Here, there is another story. Arterial PaO2 is going to be less than PAO2 (in addition to the normal minor decrs). In the case of atelectasis, alveoli are compressed. Remember, when alveloi are compressed, you get hypoxic vasoconstriction shunting the blood away from these collapsed alveoli. Basically, there is no alveoli to perfuse these vessels, so you have deoxygenated blood comming back to the left heart. Likewise, in R--L shunts, same scenario. And, giving these people O2 will not increase in the PO2 significantly (this is usually how u can differentiate a diffusion deefct vs. shunt, because in the latter you won't see an increase in PaO2 after giving O2). And, again, this is because you have collapsed alveoli, no matter how much O2 you give, it won't make a difference.
3. Perfusion defect - dead space: PE, etc. Think of this as acting like the "apex" (ventilation > perfusion, so you get better gas exchange-->increased O2, decreased CO2-->resp alk)--so these people have increase V/Q with a small thrombus (unless of course there is a saddle embolus or something, where there is complete loss of blood flow). But, usually, there are other capillaries that can compensate. So, here, giving O2 will increase PaO2.
4. Emphysema (COPD): think of this as the "apex" as well. Here the alveoli are dilated (ventilation>>perfusion, despite ventilation being decrs), but this produces different acid base distrubances because, despite having dilated alveoli, and increased ventilation compared to the little blood flow, you have increases in C02 and decrease in O2, becuase you are not able to expel the CO2 out. And, pt will respond with O2. And, that's simply because their ventilation is decreased (not able to expel CO2 and exchange for O2).
Hope this helps.
