Pulse oximetry is a simple but fundamental medical tool used to measure blood oxygen saturation, a critical indicator of a person's respiratory health. Its operation is based on principles of photometry, involving the emission of light through a tissue, usually the end of a finger, and the measurement of the amount of light absorbed by oxygenated and deoxygenated haemoglobin in the blood.

The pulse oximeter, the device used to carry out this measurement, consists of a small clip or probe that is placed on a finger, ear or toe. When activated, it emits two types of light: red and infrared. These wavelengths of light are absorbed differently by oxygenated and deoxygenated haemoglobin. The information on the amount of light absorbed is processed to determine the oxygen saturation of the blood, expressed as a percentage.

Pulse oximetry is an invaluable tool in the medical field and is used in a variety of clinical situations. It is commonly used to monitor patients during surgery, invasive medical procedures or after traumatic events. It is also used in the care of patients with chronic respiratory conditions, such as chronic obstructive pulmonary disease (COPD) or cystic fibrosis, to assess the effectiveness of oxygen therapy and detect early respiratory problems.

In addition, pulse oximetry is a crucial tool in the monitoring of patients with COVID-19, as it helps detect early signs of hypoxia, a dangerous condition in which oxygen levels in the blood are low. It is also used in intensive care settings to monitor critically ill patients to ensure they receive adequate oxygen.

In short, it is a non-invasive technique that provides vital information on blood oxygen saturation and plays a crucial role in medical care, from monitoring surgical patients to managing chronic respiratory diseases and early detection of oxygenation problems. This small device has proven to be an essential tool in modern medical care.