A blue colour of the tongue. The lips may also appear blue instead of the normal pink. Central cyanosis is a very important and dangerous sign which indicates that the cells are not receiving enough oxygen. Cold hands and feet may show peripheral cyanosis. Always look for central cyanosis if a child has peripheral cyanosis.

Pulse oximetry is a very useful method of assessing the oxygen saturation (the amount of oxygen being carried in the red cells of the blood). The normal oxygen saturation is above 95% (above 92 % in newborn infants). An oxygen saturation below 90% is abnormal and an indicator for oxygen therapy. A pulse oximeter (or oxygen saturation monitor) is used for measuring the oxygen saturation. The probe is clipped onto the child’s finger, hand or foot and the device displays the heart rate and oxygen saturation.

As central cyanosis is an important sign of respiratory failure, measuring the oxygen saturation is very useful.