An infant is born with cells that have the capacity to carry oxygen to all the tissues in the body. These red blood cells contain the protein hemoglobin, which carries the oxygen. Oxygen saturation is a measure of how much oxygen is bound to the hemoglobin, and is measured as a percentage. Oxygen saturation levels may be determined in several ways, including pulse oximetry probes, lab tests, or arterial pressure monitors. In infants, oxygen saturation levels are typically measured by a pulse oximetry sensor that is placed on the foot.
Normal Levels
A baby born after 37 weeks gestation should have an oxygen saturation between 93 and 100 percent, states Dr. Robin Steinhorn, a neonatologist at Children's Memorial Hospital in Chicago. This range is considered normal for a baby who is born without any problems surrounding the heart or lungs. A baby who has an oxygen saturation that drifts below 90 percent needs supplemental oxygen and should be tested for illnesses or genetic defects that may be causing the decline.
Preterm Infants
A premature baby, or one who is born before 37 weeks gestation, may have a lower oxygen saturation. For babies that are born several weeks early, lung tissue may be underdeveloped and the lungs cannot provide proper oxygenation. Because of this, oxygen saturations in a premature baby may be lower and may require supplemental oxygen to keep levels above 93 percent. Depending on hospital guidelines, some physicians allow oxygen saturation levels in premature babies to remain lower until the baby grows and her lungs mature.
High Levels
High levels of oxygen are associated with retinopathy of prematurity, an eye disease that causes blindness. Because oxygen saturation monitors only reach a level of 100 percent, babies who are given supplemental oxygen may be kept at high saturation levels without the ability to control exactly what the level should be. For example, a baby may have an oxygen saturation of 100 percent while using two liters of oxygen, but may also have the same outcome using only one liter. Continuously keeping a baby's oxygen saturation level at 100 percent with extra oxygen when he does not need it, can contribute to over oxygenation of the tissues. This leads to changes in the tiny vessels of the eye, resulting in retinopathy of prematurity.
References
- Stork Net: Oxygen Saturation
- The Low Vision Gateway: Understanding Retinopathy of Prematurity
- American Association of Critical Care Nurses: Oxygen Saturation Monitoring by Pulse Oximetry
- "Newborn Intensive Care: What Every Parent Needs to Know"; Jeanette Zaichkin; 2002
