( ( Because ( ( the ( brain stem ) ) ( regulates ( breathing ( by ( monitoring ( ( the level ) ( of ( blood CO2 ) ) ) ) ) ) ) ) ) ( , ( hypocapnia ( ( can ( suppress ( ( breathing ( to ( ( the point ) ( of blackout ) ) ) ) ( from ( cerebral hypoxia ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN Because) (S (NP (DT the) (NN brain) (NN stem)) (VP (VBZ regulates) (S (VP (VBG breathing) (PP (IN by) (S (VP (VBG monitoring) (NP (NP (DT the) (NN level)) (PP (IN of) (NP (NN blood) (NN CO2)))))))))))) (, ,) (NP (NN hypocapnia)) (VP (MD can) (VP (VB suppress) (S (VP (VBG breathing) (PP (TO to) (NP (NP (DT the) (NN point)) (PP (IN of) (NP (NN blackout))))) (PP (IN from) (NP (JJ cerebral) (NN hypoxia))))))) (. .)))
Because the brain stem regulates breathing by monitoring the level of blood CO2, hypocapnia can suppress breathing to the point of blackout from cerebral hypoxia.
(ROOT (S (NP (DT The) (NN brain) (NN stem)) (VP (VBZ regulates) (NP (NP (DT the) (NN rate)) (PP (IN of) (NP (NN breathing))))) (. .)))