( ( When ( you ( ( descend ( under water ) ) ( while ( breathing ( compressed air ) ) ) ) ) ) ( , ( ( ( the ( increased pressure ) ) ( of ( ( the air ) ( you ( 're breathing ) ) ) ) ) ( ( causes ( more ( nitrogen ( to ( dissolve ( in ( ( the blood ) ( ( circulating ( through ( your lungs ) ) ) ( than ( exists ( in ( ( the blood ) ( when ( you ( are ( above water ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (PRP you)) (VP (VBD descend) (PP (IN under) (NP (NN water))) (SBAR (IN while) (S (VP (VBG breathing) (NP (JJ compressed) (NN air)))))))) (, ,) (NP (NP (DT the) (VBN increased) (NN pressure)) (PP (IN of) (NP (NP (DT the) (NN air)) (SBAR (S (NP (PRP you)) (VP (VBP 're) (VP (VBG breathing)))))))) (VP (VBZ causes) (NP (JJR more) (NN nitrogen) (S (VP (TO to) (VP (VB dissolve) (PP (IN in) (NP (NP (DT the) (NN blood)) (VP (VBG circulating) (PP (IN through) (NP (PRP$ your) (NNS lungs))) (SBAR (IN than) (S (VP (VBZ exists) (PP (IN in) (NP (NP (DT the) (NN blood)) (SBAR (WHADVP (WRB when)) (S (NP (PRP you)) (VP (VBP are) (PP (IN above) (NP (NN water))))))))))))))))))) (. .)))
When you descend under water while breathing compressed air, the increased pressure of the air you're breathing causes more nitrogen to dissolve in the blood circulating through your lungs than exists in the blood when you are above water.
(ROOT (S (SBAR (IN As) (S (NP (DT a) (NN diver)) (VP (VBZ descends)))) (, ,) (NP (NP (DT the) (NN increase)) (PP (IN in) (NP (NN pressure)))) (VP (VBZ causes) (NP (NP (DT the) (NN body) (POS 's)) (NN air) (NNS pockets)) (PP (IN in) (NP (NP (DT the) (NNS ears) (CC and) (NNS lungs)) (PP (TO to) (NP (NNS compress)))))) (. .)))