Before and at the end of 2 week treatment , the clinic responses of the two regimens were evaluated , plasma levels of endothelin-1 ( ET-1 ) and nitric oxide ( NO ) were determined ; arterial oxygen partial pressure ( PaO2 , mean pulmonary arterial pressure ( mPAP ) , outflow tract of right ventricle ( RVOT ) , and internal diameter of right ventricle ( RV ) were measured .