Pulse oximeter

A pulse oximeter is a medical device that allows the monitoring of a patient’s hemoglobin oxygenation by a non-invasive method.

A pulse oximeter uses a sensor that shines light in both red and infrared wavelengths on a part of the body that is relatively “transparent” and has good arterial pulse blood flow (e.g. finger, earlobe). The percentage of oxygen saturation is calculated and reported as the % SpO2.

Pulse oximetry was developed in 1972 by Takuo Aoyagi and Michio Kishi, bioengineers, of Nihon Kohden using red infrared light at the point of measurement.

In 1981 pulse oximetry was commercialized, finding its place in respiratory care after being used in operating rooms to monitor oxygen levels in the user.

Prior to the application of oximetry technology, measurement of patient oxygenation could only be determined invasively from arterial blood gases.

With the introduction of oximetry, a non-invasive, continuous measurement of patient oxygenation is possible. It revolutionized the practice of anesthesia and greatly improved patient safety.

From the operating room, the use of oximetry quickly spread throughout the hospital, first in the recovery room, and then in various intensive care units. Pulse oximetry was of particular value in the neonatal unit, where patients do not progress well with inadequate oxygenation. In addition, obtaining arterial blood gases from sick neonatal patients is extremely difficult.

In 2009, the world’s first Bluetooth-enabled finger pulse oximeter was created by Nonin Medical, allowing physicians to remotely monitor patients’ pulse rates and oxygen saturation levels. It also allows patients to monitor their health through online records thus contributing to the evolution of telemedicine.

Acceptable physiological limits are 95 to 99 %.

Pulse oximetry is a particularly convenient non-invasive method of measurement. It uses a pair of small light-emitting diodes (LEDs) that emit a light diode through the patient’s body.

A pulse oximeter is a medical device that indirectly monitors the patient’s blood oxygen saturation (as opposed to measuring oxygen saturation directly, through a blood sample) and changes in blood volume in the skin, creating a pleth curve graph.

Most monitors also display heart rates.

A pulse oximeter is useful in any setting where the patient’s oxygenation is unstable. Assessing the patient’s need for oxygen is the most essential element for life. Human life does not thrive in the absence of oxygen. Although a pulse oximeter is used to monitor oxygenation, it cannot determine oxygen metabolism or the amount of oxygen used by a patient. For this purpose, it is necessary to measure carbon dioxide (CO2). However, the use of a pulse oximeter to detect hypoventilation is reduced by the use of supplemental oxygen.

Because of their simplicity and speed, oximeters are critical in emergency medicine and are also very useful for patients with respiratory or cardiac problems, especially COPD, or for diagnosing certain sleep disorders such as apnea and hypopnea. Their portable battery operation is useful for pilots working in pressurized aircraft above 10,000 feet where supplemental oxygen is required. Portable oximeters are also useful for climbers and athletes whose oxygen levels may be reduced at high altitudes or with exercise.

Pulse oximetry measures only oxygenation not ventilation and is not a complete measurement of respiratory concentration. It is not a substitute for laboratory-tested blood gases because it provides no indication of base deficit, carbon dioxide levels, blood pH, or HCO3 concentration.

SpO2 above 95% is generally considered to be normal.

SpO2 of 92% or less indicates hypoxemia.