Postoperative PPM was defined as absent if the indexed effective orifice area ( EOA ) was > 0.85 cm ( 2 ) / m ( 2 ) , moderate if the indexed EOA was 0.65 but 0.85 cm ( 2 ) / m ( 2 ) , or severe if the indexed EOA was < 0.65 cm ( 2 ) / m ( 2 ) .