Púlsoxímeter

A puls oxímetro, also written as pulsoxímetro in some languages, is a non-invasive medical device used to estimate the oxygen saturation of arterial blood (SpO2) and the user's pulse rate. It is commonly employed in clinical settings, as well as for home health monitoring, sports, and aviation. The device typically consists of a small sensor probe placed on a fingertip, earlobe, or sometimes a toe, connected to a compact display and control unit. The sensor contains light-emitting diodes (LEDs) that emit red and infrared light and a photodetector that measures transmitted or reflected light.

Principle and readings

The sensor relies on photoplethysmography: it detects changes in light absorption caused by arterial pulsations. By comparing absorbance at the red and infrared wavelengths, the device estimates the proportion of hemoglobin carrying oxygen (SpO2) and provides a heart rate. In many models, a perfusion index or a plethysmographic waveform is also displayed.

Normal ranges and interpretation

In healthy individuals, SpO2 is typically 95–100%. Readings below 90% are often treated as clinically significant and may prompt supplemental oxygen or further evaluation, depending on the clinical context. Readouts should be interpreted by clinicians, as device readings can be influenced by several factors.

Limitations and accuracy

Pulse oximeters can be affected by poor peripheral perfusion (e.g., cold fingers, hypotension), motion, nail polish or artificial nails, skin pigmentation, ambient light, and sensor quality. Conditions such as carbon monoxide poisoning, methemoglobinemia, or abnormal hemoglobin can cause misleading readings. The accuracy is generally within about ±2% to ±3% under ideal conditions, and may be reduced at lower saturations or with artifacts.

Types and usage

Common forms include finger clip, earlobe, and wrist-worn devices, including some wearable smart devices. Proper placement, regular calibration, and adherence to manufacturer guidelines improve reliability.