Hyperventilation decrease PaCO2. Central chemoreceptors respond to low PaCO2 by vasoconstricting cerebral blood vessels.

A) Arterial Blood Oxygen Concentration: Blood Oxygen Concentration is directly related to Hb concentration and saturation (SaO2) FA2019, p. 653. Via the Bohr Effect, decreased PaCO2 will increase SaO2, thus increasing blood oxygen concentration.

B) Arterial Blood PO2: PaO2 changes in response to decreased PAO2, PIO2, or diffusion. There would be no change in PaO2 during hyperventilation (theoretically).

C) Aterial Pressure: Decreased PaCO2 is associated with vasoconstriction, which would increase blood pressure.

E) Cerebral Tissue pH would increase due to respiratory alkalosis.

One thing that always helps me remember this concept is that in the patients post brain surgery, we often HYPERventilate their vent to decrease ICP (I.E. decrease cerebral blood flow).

This is due to lower PaCO2 in the blood, and resultant vasoconstriction of the cerebral vessels.

https://en.wikipedia.org/wiki/Reflex_syncope

Vasovagal Syncope. Much easier

There is literally a UW question on this, this young lady is having a panic attack, as a result she is hyperventilating and decreasing her PaCO2, leading to hypocapnia, this stimulates vasoconstriction-> decreased cerebral blood flow -> decrease in ICP.