oksimeter

An oksimeter, commonly called a pulse oximeter, is a non-invasive device that estimates the oxygen saturation of arterial blood (SpO2) and, in many models, measures pulse rate. It is commonly used in medical settings such as hospitals and clinics, as well as at home, in sports, aviation, and high-altitude environments. A typical sensor is placed on a fingertip, toe, or earlobe and contains light-emitting diodes in red and infrared wavelengths and a photodetector. By transmitting light through the tissue and detecting how much is absorbed during the pulsing arterial blood, the device calculates the ratio of absorbed light at the two wavelengths, which is related to SpO2.

Operating principle and output: The reading is based on the differential absorption of red and infrared light by oxyhemoglobin and deoxyhemoglobin. The device displays an SpO2 value, usually as a percentage, and often also the pulse rate and a plethysmographic waveform. Some models provide additional data such as perfusion index, signal quality, or wireless connectivity.

Usage and interpretation: In healthy individuals, SpO2 typically ranges from 95 to 100%. Readings below 90% are generally considered hypoxemic and may require clinical evaluation. Pulse oximetry is a screening and monitoring tool, not a substitute for arterial blood gas testing or clinical judgment. Readings may be affected by factors such as poor peripheral perfusion, motion, cold extremities, ambient light, nail polish, artificial nails, skin pigmentation, or the presence of abnormal hemoglobins. Conditions like carbon monoxide poisoning or methemoglobinemia can also alter accuracy.

Limitations and maintenance: The device provides estimates of oxygenation, not oxygen content or ventilation status. Proper probe placement, appropriate sizing, and regular calibration or battery maintenance help ensure reliable readings.