Fundamentals Of CMS Pulse Oximeters

By Madeline Pittman


CMS pulse oximeters refer to pieces of equipment utilized to do pulse oximetry. This type of oximetry is a noninvasive technique for assessing the levels of saturation of O2 gas in human body. This device was first developed by a physician named Glenn Allan Millikan around 1940s. This first equipment operated on 2 wavelengths and was put on the ear. The 2 wavelengths were green and red filters.

This original model was later improved by some physician called Wood in 1949. Wood incorporated a pressure capsule for squeezing blood out of the ear to get zero setting in an attempt to get absolute Oxygen saturation level. The present models work on the same principals as the original one. The working principal was however difficult to implement due to unstable light sources and photocells.

Oximetry itself was first developed in 1972 by two bioengineers, Kishi and Aoyagi at Nihon Kohden. These two used the ratio of red to infrared light absorption of pulsating parts at measuring spots. Commercial distribution of the oximeter happened in 1981 through a company called Biox. At that time, the device was mostly used in operating rooms and companies that produced it focused most of their marketing in the same direction.

Oximetry is a crucial noninvasive technique of determining the amount of oxygen in human body. It utilizes a pair of small LEDS, light emitting diodes, which face some photodiode through a translucent portion of the body. Examples of such translucent parts are fingertips, earlobes, and toe tips. One LED is red whereas the other is infrared. The red LED is usually 660 nm while the infrared LED is 940, 910, or 905 nm.

The rate of absorption of the two wavelengths differs between the oxygenated and deoxygenated forms of oxygen within the body. This difference in absorption speed can be utilized to estimate the ratio between deoxygenated and oxygenated blood O2. The observed signal changes over some period with every heartbeat because arterial blood veins contract and expand with each heartbeat. The monitor is capable of ignoring other tissues or nail make-ups by monitoring the changing portion of the absorption spectrum only.

By observing the varying absorption section only, blood oxygen monitors can display percentage of arterial hemo-globin in oxy-hemoglobin configuration. Individuals with hypoxic drive conditions without COPD have a value that stands between 99 and 95 percent. People with hypoxic drive problems usually have readings that fall between 94 and 88 percent. Often, figures of a hundred percent may or may not suggest poisoning by carbon monoxide.

An oximeter is helpful in a number of environments and applications where the oxygenation of an individual is unstable. Some of the main environments of application consist of intensive care units, hospital and ward settings, surgical rooms, cockpits in un-pressurized aircrafts, and recovery units. The drawback of these appliance is that it only measures the level of saturation of hemo-globin and not ventilation. Therefore it is not a complete estimation of respiratory adequacy.

CMS pulse oximeters appear in several models. Some are low-priced costing a few US dollars whilst others are sophisticated and costly. They may be bought from any shop, which stocks related pieces of equipment.



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