A．PaO2≤8kPa(60mmHg)，PaCO2≥6kPa(45mmHg)，SaO2<90%
B．PaO2≤8kPa(60mmHg)，PaCO2≥6.7kPa(50mmHg)，SaO2<90%
C．PaO2≤6.7kPa(50mmHg)，PaCO2≥6.7kPa(50mmHg)，SaO2<85%
D．PaO2≤6.7kPa(50mmHg)，PaCO≥8kPa(60mmHg)，SaO2<85%
E．PaO2≤6.7kPa50mmHg)，PaCO2≥6.7kPa(50mmHg)，SaO2<90%