CHF, EF 55% 6.
 complains of shortness of breath 
(ROOT (NP (NP (NP (NN CHF)) (, ,) (NP (NP (NN EF) (CD 55) (NN %)) (CD 6))) (. .)))
(ROOT (NP (NP (VBZ complains)) (PP (IN of) (NP (NP (NN shortness)) (PP (IN of) (NP (NN breath)))))))
( ( ( CHF , ) ( ( EF ( 55 % ) ) 6 ) ) . )
( complains ( of ( shortness ( of breath ) ) ) )