Pulse oximetry is a non-invasive method to measure blood oxygen saturation levels and heart rate. A pulse oximeter uses light absorption characteristics of oxygenated and deoxygenated hemoglobin to measure oxygen saturation and pulse rate. Readings between 95-100% are considered normal. While convenient, pulse oximetry has limitations and may provide inaccurate results in conditions like poor perfusion, dyshemoglobinemia, or arrhythmias. Nursing responsibilities include applying the sensor properly, documenting readings, and troubleshooting inaccurate results.