When a patient is admitted to a hospital, their care involves the continuous tracking of several physical measurements to assess their stability and overall condition. Continuous monitoring of vital signs allows the medical team to detect subtle changes that might signal an emerging health issue. Tracking oxygen levels is a particularly important aspect of patient care, as it provides real-time information about how effectively the body is supplying oxygen to its tissues. Understanding how to read this information can help family members and patients feel more informed about the care being provided.
Decoding the Hospital Monitor Display
The technology used to track oxygen levels non-invasively is called pulse oximetry, which typically involves a small clip placed on a finger, toe, or earlobe. This sensor shines light through the skin and measures how much oxygen is bound to the hemoglobin in the red blood cells as it passes through the capillaries. The resulting information is translated into two distinct numbers displayed prominently on the bedside monitor. These two values are the Oxygen Saturation, labeled as \(\text{SpO}_2\), and the Pulse Rate, often marked as PR or BPM. The \(\text{SpO}_2\) reading is usually displayed in a different color, such as blue or cyan, and appears as a percentage.
Interpreting Oxygen Saturation Levels (\(\text{SpO}_2\))
The \(\text{SpO}_2\) reading represents the percentage of hemoglobin molecules in the arterial blood that are currently saturated with oxygen. Hemoglobin acts as a vehicle carrying oxygen from the lungs to the body’s cells. For example, a reading of 98% means 98 out of 100 available oxygen-carrying sites on the hemoglobin are filled.
For most healthy adults, a normal \(\text{SpO}_2\) reading falls within the range of 95% to 100%. Levels below 95% can indicate hypoxemia, a lower-than-normal amount of oxygen in the blood. When the number dips into the low 90s, the body’s ability to oxygenate tissues is compromised and requires medical assessment.
A reading below 90% is considered low oxygen saturation and indicates a significant impairment in oxygen delivery. For patients with pre-existing lung conditions, such as Chronic Obstructive Pulmonary Disease (COPD), a physician may accept a slightly lower baseline, perhaps between 88% and 92%. A sustained reading of 88% or lower is considered critically low and usually requires immediate medical intervention.
Understanding the Pulse Rate Reading
The second number displayed by the pulse oximeter is the Pulse Rate, reflecting the patient’s heart rate in beats per minute (BPM). This reading is generated because the sensor detects the pulsating flow of blood through the capillary bed. The pulse rate offers important information about the heart’s function, even though oxygen level is often the primary concern.
For a resting adult, the normal range for the pulse rate is between 60 and 100 BPM. A rate above 100 BPM is known as tachycardia and may be caused by pain, fever, or anxiety. Conversely, a heart rate below 60 BPM is called bradycardia, which may indicate a medical issue unless the patient is a highly conditioned athlete.
Factors Affecting Accuracy and When to Call for Help
The \(\text{SpO}_2\) reading is a sensitive measurement that can be affected by several factors, sometimes leading to a temporarily inaccurate display. Patient movement is a common issue, as it disrupts the sensor’s ability to detect blood flow, causing the reading to drop or become erratic. Poor circulation to the sensor site, such as from cold hands or low blood pressure, may also result in a falsely low reading.
External obstructions like dark nail polish or artificial nails can interfere with the light transmission required for the device to function. Additionally, very dark skin pigmentation can lead to the pulse oximeter slightly overestimating the actual oxygen saturation level. If the number on the screen suddenly drops, first check the sensor’s position and ensure the patient is not moving.
Contact a nurse or doctor if the \(\text{SpO}_2\) reading remains consistently low (below 92%) despite repositioning the sensor, or if the monitor’s alarm sounds repeatedly. Alert the medical team if the patient reports new or worsening symptoms like shortness of breath, chest discomfort, or dizziness, regardless of the number displayed. The medical team should always be consulted for concerns about the patient’s condition.