Classification 1. According to blood gas 1) type I(hypoxemic RF): Pao2 <60 mmHg(8.kpa) 2 )type Il(hypercapnic RF) PaO2 <60 mmHg(8.kpa) with PaCo2 >50 mmHg(6.67 kpa8 Classification 1. According to blood gas: 1) typeⅠ(hypoxemic RF) : PaO2 <60 mmHg (8.0kpa) 2) type Ⅱ (hypercapnic RF) : PaO2 <60 mmHg (8.0kpa) , with PaCO2 >50 mmHg(6.67kpa)