Yeah, but why does dead space only affect CO2? Since Q goes up, V/Q goes down - that's V/Q mistmach which causes hypoxemia. Areas of lung that are perfused in PE have very high blood flow (Q) since blood cannot go through all normal channels due to clot. Hypoxemia occurs in PE due to V/Q mismatch. Also there is hypoxemia in PE, but not because of the dead space (because dead space doesn't case low O2). This is because patients hyperventilate to keep Co2 normal despite dead space. There is dead space, but usually not hypercapnia. Leaves more CO2 behind in the blood so CO2 rises. Air goes in and out without picking up CO2. Dead space is ventilated but not perfused. Net result: oxygen fails to improve O2.ĭead space: Has nothing to do with O2, only CO2. So oxygen does not help because it can't get to shunt areas (no ventilation) and it can get to non-shunt areas which are already fully oxygenated. Non-shunted areas are fully oxygenated (100%). In a shunt, blood good from right heart to left heart without passing ventilated areas (i.e., does not pick up oxygen).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |