Peripheral cyanosis is common in children at any age and is not important. Central cyanosis is always important but may be missed in a child with severe anaemia or children with pigmented skin. It is detected by looking at the colour of the tongue – blue colouration suggests a saturation of less than 85%. Central cyanosis is not improved by breathing 100% oxygen and its presence should be confirmed by a pulse oximeter. Long standing cyanosis may be associated with ‘clubbing’ of the nails of the hands and feet. Children who have long standing cyanosis develop compensatory polycythaemia and possibly.
