Oxygen saturation (SpO2) measures the percentage of hemoglobin in the blood carrying oxygen. Hemoglobin, a protein within red blood cells, transports oxygen from the lungs to the rest of the body. This measurement indicates respiratory function and how efficiently the lungs exchange oxygen and carbon dioxide.
Monitoring an infant’s oxygen level is relevant during sleep because breathing patterns naturally fluctuate. As a baby cycles through different sleep stages, their breathing rate and depth change, which can lead to temporary variations in oxygen saturation. Understanding what constitutes a normal reading is important for parents using home monitoring devices to avoid unnecessary concern.
Defining Normal Oxygen Saturation in Infants
For a healthy, full-term baby sleeping at sea level, the expected oxygen saturation range is generally between 95% and 100%. The median saturation for healthy infants during sleep often settles between 97% and 99%. These values indicate that the baby’s respiratory system is functioning effectively to meet oxygen demands.
It is normal for infants to experience brief, transient dips in saturation, especially during periods of active or rapid eye movement (REM) sleep. These momentary drops are physiological and typically resolve as the baby’s breathing regulates. However, any reading that remains sustained below the expected range warrants closer attention, as it suggests the body is not receiving adequate oxygen.
Understanding Pulse Oximetry Technology
Blood oxygen saturation is measured non-invasively using a pulse oximeter. This small device passes two different wavelengths of light—one red and one infrared—through a thin part of the body, such as a finger or toe. The light absorption characteristics of oxygenated and deoxygenated hemoglobin differ significantly.
By measuring the ratio of light absorbed at each wavelength, the oximeter estimates the proportion of hemoglobin carrying oxygen. The device simultaneously measures the pulse rate, which confirms the reading is accurately detecting arterial blood flow. A steady pulse reading accompanying the saturation number indicates a reliable measurement.
For infants, specialized sensors are typically placed on the foot, hand, or great toe. It is important to ensure the light emitter and the detector are positioned directly opposite each other on the limb, with no gaps, to prevent inaccurate light detection. Proper sensor placement and a good signal are necessary for a trustworthy estimate of the baby’s true oxygen status.
Factors That Influence Oxygen Readings
Several factors unrelated to a baby’s health can influence the accuracy of an oxygen saturation reading. One common issue is movement artifact, where a baby’s shivering, wiggling, or crying interferes with the sensor’s ability to detect a steady pulse, leading to falsely low or erratic readings. The sensor must be held still to capture a stable waveform for an accurate result.
Environmental conditions are also a factor. People living at high altitudes naturally have slightly lower baseline oxygen levels, meaning the accepted normal range for infants may shift downward by a few percentage points depending on the elevation. Furthermore, darker skin pigmentation may sometimes cause the device to overestimate or underestimate the reading due to how light is absorbed by the skin.
The baby’s medical history, particularly prematurity, must also be considered. Infants born prematurely may have an acceptable baseline oxygen saturation lower than 95%, often defined by their pediatrician as being above 90%. These variations highlight why a single reading should not be interpreted in isolation but rather as part of a broader clinical picture.
Identifying and Responding to Low Oxygen Levels
A sustained drop in oxygen saturation below a specific threshold is medically defined as hypoxemia. While the threshold can vary, a reading that remains below 90% for a prolonged period is generally considered a low oxygen level requiring intervention. Some clinicians may recommend seeking advice if the SpO2 is consistently below 93%.
When a low reading occurs on a home monitor, the first step is to immediately check the sensor placement to rule out an artifact or poor connection. Gently stimulating the baby, such as by picking them up or repositioning them, can often cause them to take a deeper breath, resolving a transient dip. If the reading remains low after adjusting the sensor and stimulating the baby, medical attention should be sought immediately.
Critical physical signs that signal a medical emergency include cyanosis, which is a bluish discoloration of the lips, face, or nail beds. Other signs of serious respiratory distress include labored or heavy breathing, flaring nostrils, visible indrawing of the chest (retractions), or excessive lethargy and difficulty waking. A sustained low saturation reading combined with any of these physical symptoms requires an immediate call to emergency services.