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NBME 22 Answers

nbme22/Block 1/Question#33

A 32-year-old woman begins to hyperventilate and ...

Cerebral blood flow

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submitted by keycompany(127),

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.

keycompany  EDIT: Via the **Haldane Effect**, not the Bohr Effect. +  
impostersyndromel1000  excellent response +  

 +1  upvote downvote
submitted by seagull(461),


Vasovagal Syncope. Much easier