Why the need for a Pulse Oximeter?
The article “Repairing a Stethoscope is ever so easy” started with an hilarious opening paragraph stating that Stethoscopes are the only point of care device you’ll find a Nigerian doctor armed with once the ward coat is excluded.
In a similar fashion, this article is premised on the need for proliferation of pulse oximeters among healthcare professionals. It is by far the most important point of care device a healthcare professional can be armed with in this critical period of the covid-19 pandemic as opposed to the proliferation of N95 respirators – of course the respirator isn’t a diagnostic device.
A Pulse oximeter is a non-invasive device that measures blood oxygenation in well-perfused areas of the body with the sensor placed on extremities such as finger, toe, ear lobe, or forehead depending upon its design – the finger probe oximeter’s measure of oxygen saturation of the hemoglobin is implicated in large organs, as with the respiratory organs in the case of the novel corona virus. It detects hypoxia long before the presentation of symptoms.
The device can also report the heart rate and the plethysmograph using the plethysmographic pulse from the artery. Its wide spread use has reduced the use of blood gas analysers, besides they are nowhere as complex to maintain as blood gas analysers.
In a healthy individual, only a 2% deviation from a 100% perfect oxygen saturation in hemoglobin is acceptable in the arteries. Hence spO2 reading below 98% is unacceptable.
The pulse oximeter works on the principle of light absorption given that venous blood with dark coloration, and arterial light colored blood are discovered to have different light absorption levels.
It operates using two frequencies of light of wavelength; Red (650nm) to measure hemoglobin and Infrared (950nm) to measure oxyhemoglobin concentration. The absorption ratio is a good indicator of the oxygen carrying capacity of blood, determines oxygen saturation, and is represented as %spO2.