A pulse oximeter is a small, non-invasive device that measures the oxygen saturation level in your blood (SpO2). It works by shining a light through your skin to measure oxygen carried by red blood cells. Using the device correctly helps ensure accurate readings, including proper finger selection and placement.
Selecting the Best Finger
For accurate readings, the index or middle finger are generally recommended. These fingers offer optimal blood flow and suitable tissue thickness for the device’s sensors. Some studies suggest the right middle finger might provide the highest oxygen saturation values.
Position your finger with the nail facing upwards, fully inserted into the clip. Maintaining a steady hand and avoiding movement during the measurement is also important. While other fingers like the pinky or thumb can be used, they may be less ideal due to variations in size or reduced circulation, which could affect consistency.
Other Factors Affecting Accuracy
Beyond finger selection, several factors influence accuracy. Nail polish, especially dark colors, can interfere with the device’s light signals. Artificial nails also block this light, leading to inaccurate results. It is advisable to remove any nail polish or artificial nails before taking a reading; if removal is not possible, try placing the sensor sideways on the fingertip.
Cold hands or poor circulation can reduce blood flow to the fingertips, making it difficult for the oximeter to detect a strong signal. Warming your hands before a reading can help improve signal strength and accuracy. Additionally, any movement during the measurement, whether from the patient or the device itself, can cause erratic readings or signal loss. Remaining still and resting your hand below heart level can help ensure a stable measurement.
Improper placement of the probe, such as not fully inserting the finger or using a finger-specific probe on another body part, can lead to incorrect readings. External light sources (e.g., bright sunlight, fluorescent lights) can interfere with sensors. Shield the device from direct bright light. Skin tone can also play a role, as some studies indicate oximeters may overestimate oxygen levels in individuals with darker skin pigmentation, particularly when actual levels are lower. Research is ongoing to improve device performance across all skin tones.
Understanding Your Readings
A pulse oximeter displays two main readings: oxygen saturation (SpO2) and pulse rate (BPM). SpO2 indicates the percentage of oxygen in your blood; BPM is your heart rate. For most healthy adults, normal SpO2 falls between 95% and 100%. A healthy pulse rate typically ranges from 40 to 100 beats per minute.
Understand what your readings mean for your health. An SpO2 level consistently below 95% may suggest a potential issue. Readings below 92% are considered low, indicating a more significant concern. If your SpO2 consistently reads 88% or lower, or if you experience symptoms like shortness of breath, chest pain, or significant changes from your usual readings, consult a healthcare provider promptly.