How do I make sure I'm getting an accurate reading when I use pulse oximetry for my adult patient?-A.G., N.Y.
Richard L. Pullen, Jr., EdD, RN, replies: Choose a well-perfused sensor application site-the finger, toe, nose, earlobe, or forehead-then choose a sensor that's appropriate for the patient's age, weight, anticipated duration of monitoring, level of patient activity, and infection control issues. Avoid placing a sensor on edematous tissue or placing a sensor on the same extremity being used for automated noninvasive BP monitoring, which can interfere with SpO2 readings.
Apply sensors to clean and dry application sites, making sure that the photodetector and light-emitting diode are properly aligned. If you're using a finger for the application site, remove any nail polish or acrylic nail. Make sure the sensor is securely in place but isn't too tight, which could impair blood flow and reduce the accuracy of readings. Use the ring finger instead of the index finger because it's less prone to movement.
Ensure that all connections are secure and that the patient's radial or apical pulse rate correlates with the heart rate displayed on the monitor. Oximeters require a steady pulse signal; conditions that affect the consistency of the pulse, such as cardiac dysrhythmias, will reduce accuracy.
Other causes of possibly inaccurate SpO2 measurements include abnormal hemoglobin, such as methemoglobinemia, and significant carboxyhemoglobin levels caused by carbon monoxide poisoning. In addition, inaccurate measurements may occur with abnormally low oxygen saturation levels.
Read the SpO2 measurement on the digital display when it reaches a constant value, usually in 10 to 30 seconds. Because bright lights may interfere with the light source on the oximeter sensor, keep ambient lighting low or cover the sensor with a sheet or towel.
Assess circulation distal to the sensor site according to facility guidelines to ensure correct sensor application and optical alignment, as well as skin integrity. Change sensor sites according to facility policy.