Theory 02/Space Medicine & Microgravity Physiology
Space Anaemia Is a Volume Reset
Spaceflight anaemia is a regulated reduction in red cell mass matched to a reduced plasma volume rather than destruction of healthy cells, so it should resolve with volume restoration rather than with iron or erythropoietin.
01The mechanism
Fluid shifts in microgravity reduce plasma volume. The body adjusts red cell mass to maintain a constant concentration, which registers as anaemia by count while oxygen-carrying capacity per unit volume is preserved.
On return, volume expands and the mass should recover without intervention; treating it as a deficiency risks overload.
02What this is not
Those attribute the drop to red cell destruction. This attributes it to a set point, which predicts recovery on volume restoration.
03Predictions
- P1Red cell mass should recover with plasma volume on return.
- P2Iron therapy should not accelerate recovery.
04Refutation
Persistent destruction with volume restored would favour haemolysis.