Overnight pulse oximeters are medical devices used to noninvasively monitor oxygen saturation in the body of a patient. This equipment is used in a medical method called pulse oximetry. The equipment was invented by a German physician in the year 1935. Since that first invention, there have been many other physicians who have added components to the device with a bid to make it more effective.

Oximetry uses two tiny LEDs, light emitting diodes that face a photodiode on the other side through a translucent section of the body. Fingertips, earlobes, or feet in the cases of infants can be made use of. One of the diodes is red and has wavelength of around 660 nm. The other diode is usually infrared with 905, 910, or 940 nm of wavelength. The speed of absorption of the two wavelengths differs significantly between deoxygenated and its oxyhaemoglobin counterpart.

Due to the differences in the absorption rate of infrared and red wavelengths, oxyhemoglobin and deoxyhemoglobin ratio could be calculated. At wavelengths of between 590 and 805 nm, absorbance of deoxyhemoglobin and oxyhemoglobin remains similar. Earlier devices used these range of wavelengths to rectify hemoglobin concentration.

The monitored signal varies over time with the heart beat since the arterial blood vessels contract and expand with every heartbeat. By analyzing the varying section of the absorption spectrum only, a monitor is able to leave out nail polish or other tissues. By ignoring polish on nails and other tissues, the monitor can discern only absorption that is caused by arterial blood. It is therefore an important requirement to detect a pulse in this exercise, otherwise the oximetry will not work.

The monitor that monitors the level of blood oxygen displays the percentage of hemoglobin in the arteries in oxyhemoglobin configuration. For patients who do not have COPD and hypoxic drive problem, the normal acceptance range lies between ninety five to ninety nine percent. Patients with hypoxic problem expect values between eighty eight to ninety four percent. Carbon monoxide poisoning is indicated by a value of one hundred percent.

Oximetry is different from other methods of monitoring the level of oxygen in blood because it is an indirect approach. The equipment can be integrated into multi-parameter patient monitoring systems. Most of them also indicate the pulse rate of an individual under monitoring. Overnight pulse oximeters are normally portable so that they can be carried into homes for home-based medication. They are small and operate on batteries.

These devices can be used in a wide range of applications and environments. They are used in hospital wards, emergency units, urgent care facilities, unpressurized aircrafts, and intensive care units among many others. They are used to assess the need and efficiency of supplemental oxygen to people. The device however cannot determine the rate of metabolism of oxygen in the body. For this reason, it should be used with carbon dioxide monitoring devices complimentarily.

Overnight pulse oximeters are vital for patients in critical medical conditions. They alert health staff of abnormalities in levels of oxygen in patients. Improvements in technology have rendered it possible to control them remotely for purposes of convenience.