For both groups , the levels of plasma ET-1 were positively correlated with values of mPAP , RVOT , and RV ( r = 0.710 , 0.853 , and 0.766 , respectively , all P = 0.000 ) , and negatively correlated with plasma NO and PaO2 ( r = - 0.823 , and - 0.752 , respectively , all P = 0.000 ) .