get pumped 👊 for more pulm #twearls from @galbamd tomorrow, but here's what we learned after part 1 of gas exchange today...
1/ 72yoM with COPD (FEV1 0.5L ~25% predicted) is admitted with a COPD exacerbation with accessory muscle use, RR 33, SpO2 84% and ABG 7.3/80/55. He is placed on NRB with improvement in SpO2 to 100%. He becomes obtunded and repeat ABG is 7.1/110/50. Why?
1. loss of pulmonary hypoxic vasoconstriction👉V/Q
mismatch
2. Haldane effect: during conditions of increased oxygen
tension, there is increased CO2 displacement from Hgb
in the pulmonary circulation
2/ just a reminder: 😅hypoxia (state of O2 deficiency)=/= hypoxemia (low arterial blood O2 tension) BUT...
causes of hypoxia include:
--insufficient O2 delivery to tissues (ischemia, anemia, CO poisoning etc)
--insufficient utilization of oxygen (mitochondrial disorders, sepsis)
3/ here's an easy to remember rule of thumb 👍
-PaO2 40-50-60
👇👇👇
-SaO2 70-80-90
4/ Remember! A VBG is pretty good for most of what you need when on the wards.
-pH is ~0.02-0.04 units lower
-pCO2 is ~3-8mm Hg higher
5/ Causes of reduced DLCO?
-abnormal membrane (ILD, emphysema)
-abnormal Hgb (anemia, CO-Hb)
-⬇️ capillary blood volume (PAH, CTEPH, emphysema)
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