pulsoximeters

Pulse oximeters are noninvasive medical devices that estimate the oxygen saturation of arterial blood (SpO2) and monitor pulse rate. They typically use photoplethysmography, emitting red and infrared light through a thin part of the body such as a fingertip or an earlobe and detecting the amount of light that passes through or is reflected. By comparing the absorption at the two wavelengths, the device derives an estimate of SpO2 and, from the pulsatile component of the signal, the heart rate. Many models also display a waveform and a perfusion index.

Pulse oximeters are widely used in hospitals, clinics, and home settings to assess respiratory status, monitor patients under anesthesia, and guide treatment for conditions such as chronic obstructive pulmonary disease, heart failure, sleep apnea, and during high altitude exposure. They come in several form factors, including fingertip, handheld, and wearable wrist or ear devices, with some enabling continuous monitoring and wireless data transmission.

The accuracy of pulse oximetry is influenced by factors such as motion, poor peripheral perfusion, skin pigmentation, nail polish or artificial nails, ambient light, and the presence of abnormal hemoglobins such as carboxyhemoglobin or methemoglobin. In ideal conditions, SpO2 readings are typically within about 2 percentage points of arterial oxygen saturation measured by co-oximetry, but performance can degrade in low flow states or critical illness. Therefore, pulse oximetry complements, rather than replaces, blood gases or clinical judgment.

Pulse oximeters are noninvasive and generally safe for home and clinical use, but readings should be interpreted by qualified personnel for diagnosis and treatment decisions.

The technique was developed by Takuo Aoyagi in the 1970s and widely commercialized in the 1980s, becoming a staple in patient monitoring.