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In FA pg 507 it says that in complete shunt 100% O2 does not help (which is correct)
it then says that in Dead space assuming its not complete, O2 improves Po2
It is true that 100% O2 doesnt help either a COMPLETE shunt or dead space.
I think its misleading tho:
it fails to mention that actually 100% O2 helps BOTH partial dead space and partial shunt, and that in fact 100% O2 is much much more helpful for partial shunt than for partial deadspace, and that 100% O2 only marginally helps dead space.
(the reason is because in dead space the defect is in perfusion, not ventilation, so the little amount of blood that does get through is already maximally saturated, and 100% o2 only improves dissolved o2, while in contrast in shunt there is a defect in ventilation, so providing 100% O2 will greatly change the Alveolar O2 conc.....)
it then says that in Dead space assuming its not complete, O2 improves Po2
It is true that 100% O2 doesnt help either a COMPLETE shunt or dead space.
I think its misleading tho:
it fails to mention that actually 100% O2 helps BOTH partial dead space and partial shunt, and that in fact 100% O2 is much much more helpful for partial shunt than for partial deadspace, and that 100% O2 only marginally helps dead space.
(the reason is because in dead space the defect is in perfusion, not ventilation, so the little amount of blood that does get through is already maximally saturated, and 100% o2 only improves dissolved o2, while in contrast in shunt there is a defect in ventilation, so providing 100% O2 will greatly change the Alveolar O2 conc.....)
