CHF - no more Lasix?

[Kiwiology]

They certainly have been used to deal with the fluid shift, but on the erroneous assumption that there is an overload of fluid. The key term is 'fluid shift'. Eliminating the fluid in the system does not necessarily correct the fluid shift (it's not systemic overload we are usually worried about with ACPE - it's fluid in the wrong place, not too much fluid) and can lead to further problems with electrolytes (K+ in particular of course) and long term poor outcomes. Nitrates and ACEI's all serve to better correct the imbalance between hydrostatic and colloid oncotic forces that are the main problem to allow the fluid to shift back (or rather be taken up by the lymphatic system) and CPAP splints alveoli open to improve oxygenation and the problems that come from the V/Q mismatch (and shunt if really bad) (hopefully someone else can explain that better than me)

You are pretty much dead on; the key term here is a SHIFT of fluid and a mismatch between the intravascular and interstitial fluid. That which is in the vasculature of the pulmonic circulation is not being ejected into the systemic circurt by the heart hence the osmotic presssure increases and ... suprise, simple fluid dynamics tells us that the fluid will take the path of least resistance in this case straight into the lungs.