Unable to keep fluid down.
 Patient has no problem drinking fluids
(ROOT (S (S (ADJP (JJ Unable) (S (VP (TO to) (VP (VB keep) (NP (NN fluid)) (PRT (RB down))))))) (. .)))
(ROOT (S (NP (NN Patient)) (VP (VBZ has) (NP (NP (DT no) (NN problem)) (NP (NN drinking) (NNS fluids))))))
( ( Unable ( to ( ( keep fluid ) down ) ) ) . )
( Patient ( has ( ( no problem ) ( drinking fluids ) ) ) )