A pulse oximeter is a clip-like instrument, typically placed on a fingertip, that monitors the efficiency of the body’s respiratory system. It uses beams of light to estimate the amount of oxygen carried by the blood. The primary function is to measure oxygen saturation (SpO2) and simultaneously determine the user’s pulse rate. The device provides a quick, convenient way to see how well oxygen is being distributed throughout the body.
Getting an Accurate Reading
To ensure the reading from a pulse oximeter is reliable, proper technique and preparation are necessary. The finger being tested should be warm, relaxed, and held still, ideally below the level of the heart, to promote good blood flow. Cold hands or any movement during the measurement process can cause unreliable readings, as the device struggles to detect a strong, consistent signal.
The presence of fingernail polish or artificial nails can interfere with the light beams the oximeter uses. These coatings can block the light transmission, so they should be removed from the chosen finger. Furthermore, skin tone is a consideration for accuracy, as the natural pigment melanin absorbs the light the device emits. For individuals with darker skin tones, this absorption can potentially cause the oximeter to give a falsely high reading.
Understanding the Displayed Numbers
A pulse oximeter provides two primary measurements: Oxygen Saturation and Pulse Rate. The oxygen saturation level (SpO2) represents the percentage of hemoglobin in the red blood cells that is fully saturated with oxygen. For a healthy adult at sea level, the SpO2 reading should be between 95% and 100%.
A reading below 95% may suggest hypoxemia, a reduction in blood oxygen levels. The second number displayed is the Pulse Rate (BPM), which reflects the user’s heart rate. For most healthy adults at rest, a normal pulse rate falls within the range of 60 to 100 beats per minute, though well-conditioned athletes may have a lower resting rate.
The pulse oximeter works by shining two different wavelengths of light, red and infrared, through the tissue to measure how much is absorbed by the blood. Oxygen-rich blood absorbs less red light than blood with lower oxygen levels, allowing the device to calculate the saturation percentage.
When to Consult a Healthcare Provider
Monitoring readings over time can help establish a personal baseline, but certain numerical thresholds indicate a need for medical consultation or immediate care. For healthy individuals, a consistent SpO2 reading that falls below 92% warrants contacting a healthcare professional for advice.
A reading that is consistently 88% or lower signals severe hypoxemia and requires immediate medical attention. People managing chronic lung conditions, such as COPD, may have a lower “normal” baseline, and they should discuss their acceptable range with their doctor. The pulse rate is also a factor, and if it is unusually high or low when combined with symptoms like shortness of breath or chest pain, seek professional guidance.