A newborn baby is found to be apparently healthy at birth but after some weeks he does not seem to be thriving. When
examined, the baby is found to be centrally cyanosed, i.e. his tongue and lips appear rather blue in colour. This indicates
that the oxygen saturation of arterial hemoglobin is abnormally low. It is suspected that the cause is a congenital
abnormality of the heart, leading to abnormal shunting of the blood from one side of the circulation to the other.
Catheters are inserted allowing blood samples to be taken from a number of sites. The partial pressure of oxygen (PO2) is
measured for each sample and the results obtain are given in Table as following: