( ( ( ( ( ( The ( two-stage regulator ) ) ( allows ( ( compressed air ) ( to ( be ( inhaled ( at ( the ( ambient pressure ) ) ) ) ) ) ) ) ) , ) so ) ( ( the ( scuba diver ) ) ( can ( ( maintain ( normal ( lung volume ) ) ) ( at ( all depths ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT The) (JJ two-stage) (NN regulator)) (VP (VBZ allows) (VP (VBN compressed) (NP (NN air)) (S (VP (TO to) (VP (VB be) (VP (VBN inhaled) (PP (IN at) (NP (DT the) (JJ ambient) (NN pressure)))))))))) (, ,) (IN so) (S (NP (DT the) (NN scuba) (NN diver)) (VP (MD can) (VP (VB maintain) (NP (JJ normal) (NN lung) (NN volume)) (PP (IN at) (NP (DT all) (NNS depths)))))) (. .)))
The two-stage regulator allows compressed air to be inhaled at the ambient pressure, so the scuba diver can maintain normal lung volume at all depths.
(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)))))) (. .)))