The health of an infant is assessed in various ways, including observation and measurement of important blood components. Measurement of oxygen saturation provides information about a child’s respiratory, heart and circulatory health. It is part of an assessment of vital signs for an infant, particularly if the newborn is premature or experiences breathing difficulty.
Oxygen saturation reflects the quantity of haemoglobin in the blood that is saturated with oxygen. Haemoglobin is the component of red blood cells that binds oxygen and transports it to body tissues. Oxygen saturation is commonly measured by pulse oximetry. This instrument uses an infrared light source to detect oxygen saturation without collecting a blood sample. A pulse oximeter is typically wrapped around an infant’s foot or hand to obtain a measurement.
A healthy, full-term baby should have an oxygen saturation of 95 to 100 percent. Some health care facilities may have slightly different parameters. Full-term newborns who require supplemental oxygen after birth may have slightly lower oxygen saturation levels.
Babies born prematurely have lower oxygen saturation levels initially because their lungs are not fully developed. Normal oxygen saturation for a preterm infant is roughly 84 to 90 percent. A newborn who is unable to maintain a minimum oxygen saturation level — whether full-term or premature — may be placed on supplemental oxygen. The health care team monitors an infant’s oxygen saturation level and adjusts the flow rate and concentration of supplemental oxygen to maintain a normal level.
Infants with an oxygen saturation level below a normal level have hypoxemia — or oxygen deficiency. For an infant not wearing a pulse oximeter, hypoxemia may not be readily apparent. For example, a bluish discolouration around the lips called cyanosis is a physical sign of low blood oxygen. However, this sign often does not develop until the oxygen saturation drops to 75 percent or less in a full-term infant.
RETINOPATHY OF PREMATURITY
Maintaining a lower oxygen saturation than typically considered normal may be acceptable or preferable in some situations. Because lung tissue is one of the last to fully develop in a fetus, premature babies frequently require supplemental oxygen. Treatment with high levels of oxygen may lead to retinopathy of prematurity, an eye disorder that can lead to blindness. Adjusting the supplemental oxygen to maintain oxygen saturation at a lower level decreases the occurrence of ROP.