I stumbled upon this presentation which deals how to approach to a problem of congenital heart disease. In a newborn or an infant . It is clearly a master piece . A life time experience of a pediatrician condensed in 130 slides . It is from Kerala .India.
To quote an example from this presentation.
When you want to rule out urgently a congenial cyanotic heart disease in the bed side * What will you do ?
What is hyperoxia test ?
Axminster 100 % O2 . Measure satutration.If the PO2 crosses 200 , virtually any cyanotic heart disease is ruled out.
If it is less than 150 , it is very much likely the baby has a CHD !
(* Echocardigram may not be available everywhere . Even if it is there it needs a certain expertise to do it new-born )
Dr.S.Venkatesan MD 
• Hyperoxia test
1. This test is used for diagnosing cause of cyanosis i.e. whether due to
cardiac or noncardiac
2. 100% oxygen is administered through plastic hood for at least 10mins
3. In patient with cardiac cause i.e. right to left shunt, arterial PO2 does not
raise more than 10-30mmhg.
4. But in respiratory diseases with cyanosis, arterial PO2 raises more than
100mmhg.
5. Limitation of Hyperoxia test:
a. Total anomalous pulmonary venous connection (TAPVC) patients with
large pulmonary flow may show increase in arterial PO2 more than
100mmhg
b. Massive intrapulmonary shunts due to lung disease without cardiac
illness may not show increase in arterial PO2 more than 100mmhg