Answer : Peripheral cyanosis reduces or disappears , while central cyanosis persist.
This is how , 99% of cardiology fellows answered in one of my classes ! And they were quoting few references for it .
Is that correct ? If so , what is the mechanism of oxygen response ?
Comments welcome . Discussion will start soon .
Dr.S.Venkatesan MD 
Dear sir,
Cynocis or blueish discoloration is because of reduced oxygen saturation in blood and cause can be anything from hypoxia to cold or poisoning, or any mechanism where oxygen fixation to haemoglobin is hampered.
In pherifheral cynocis, blueness is obvious externally and may help with oxygen but not always.
But in central cynocis (cong. heart disease, in one lung ventilation and other lung is normaly inflated and perfused,) there is a mis match of ventilation and perfusion, if V/Q is less than 25% or so, cynocis improoves with O2 but beyond that it is very difficult unless a high atmos. pressure O2 supply is given.
so improvement will depend on cause of cynocis and is not absulatly depend on central or peripheral type