When a baby’s oxygen level appears low on a monitor, it raises immediate concern about their health and ability to breathe. Oxygen saturation (SpO2) is a measurement that estimates the percentage of hemoglobin in the blood carrying oxygen. Oxygen is transported from the lungs to all the body’s tissues via red blood cells. A significantly low reading, known as hypoxemia, indicates that the infant is not delivering enough oxygen to meet their needs. Understanding the causes behind a drop in this number is the first step toward determining the right course of action.
Normal Oxygen Saturation Levels and Measurement
For most healthy infants, the expected oxygen saturation level is between 95 and 100 percent when breathing room air. Readings consistently below 95% are considered abnormal and may warrant further evaluation by a healthcare professional. The device used to obtain this measurement is called a pulse oximeter, which is a non-invasive tool commonly applied to a baby’s foot, hand, or finger.
The oximeter works by shining two wavelengths of light—red and infrared—through the skin and measuring how much light is absorbed by the blood. Oxygenated hemoglobin absorbs light differently than deoxygenated hemoglobin, allowing the device to calculate the estimated oxygen saturation level. This reading, presented as a percentage, is a quick estimate of the oxygen content in the arterial blood.
Non-Disease Related Causes of Low Readings
Sometimes, a low SpO2 number is a false alarm caused by technical or environmental factors rather than a true medical problem. Poor sensor placement is a frequent culprit, as the oximeter requires a clear pulse signal to function accurately. Excessive movement or crying by the baby can also disrupt the reading, leading to a temporarily unreliable display.
Physiological factors, such as cold extremities, can cause a low reading because reduced blood flow at the sensor site makes it difficult for the oximeter to detect a strong pulse. Ensuring the baby’s foot or hand is warm and still can often correct these transient issues. Environmental conditions like high altitude, where the air naturally contains less oxygen, can also result in a slightly lower but normal baseline saturation.
Respiratory System Conditions
The most frequent medical causes for an infant’s low oxygen level are related to the respiratory system, affecting the lungs’ ability to exchange oxygen and carbon dioxide. Infections are a prime example. Viruses like Respiratory Syncytial Virus (RSV) commonly cause bronchiolitis, which inflames and clogs the small airways. Pneumonia, a bacterial or viral infection that causes fluid and inflammation in the air sacs, similarly impairs gas exchange efficiency.
In premature infants, Respiratory Distress Syndrome (RDS) is a common concern because their lungs lack sufficient surfactant, a substance that keeps the tiny air sacs open. Without surfactant, the lungs can collapse, requiring the baby to work much harder to breathe and limiting oxygen uptake. Airway obstruction, whether from severe nasal congestion or an inhaled foreign object, also physically blocks the path of air. Periods of apnea, the temporary cessation of breathing, are particularly concerning in premature babies.
Circulatory and Systemic Causes
When the low oxygen level is not solely due to a lung issue, the cause may lie in the circulatory system or a body-wide condition. Congenital heart defects (CHD) can directly lead to low saturation if the heart structure causes oxygen-rich and oxygen-poor blood to mix, or if blood bypasses the lungs entirely. Defects referred to as “cyanotic” heart disease result in a visible bluish tint to the skin.
Severe anemia is another systemic cause, a condition where the baby has too few red blood cells or insufficient hemoglobin, the protein that carries oxygen. Even if the lungs are functioning perfectly, the blood lacks the necessary vehicles to transport adequate oxygen to the body’s tissues, leading to hypoxemia. Furthermore, severe body-wide infections like sepsis can cause shock, resulting in low blood pressure and poor circulation. This circulatory shock impairs the delivery of oxygenated blood to the tissues.
Recognizing Signs of Distress and Seeking Help
A low oxygen saturation reading is often accompanied by observable signs that indicate the baby is struggling to breathe. Cyanosis, a bluish or grayish discoloration of the lips, tongue, or skin, is a significant sign of severe hypoxemia. The baby may also exhibit signs of increased work of breathing.
These signs include nasal flaring, where the nostrils widen with each breath, and retractions, which are visible pulling in of the skin between the ribs or at the base of the neck. Audible signs, such as grunting with every exhale, indicate the baby is trying to keep their air sacs open. If a baby appears lethargic, is difficult to wake, or displays these severe signs of respiratory distress, immediate emergency medical attention is required.