Give 100% O2 for 10 min → measure pre-ductal ABG (R radial)

• PO2 < 150 mmHg → cardiac causes
• PO2 > 250 mmHg → noncardiac causes

*arterial blood gas =/= oxygen saturation

In !Cyanotic CHD (cardiac causes):

• O2 Sat can improve with O2 therapy

• arterial blood gas cannot improve with O2 therapy

  • With O2 therapy, PO2 can go to 600

    

  Source 2: < 150