Oxymetry, Yes Please
Everyone, not just doctors, knows how important it is to be aware of her or his body weight, temperature, heart rate, arterial pressure and respiratory rate. These are all vitals which supply a simple number to measure our state of health. However few people are aware of their blood oxygen level.
The vitals that everybody knows and which measure our state of health.
Someone perhaps has heard of Oximetry, without knowing that this is another vital sign expressed by a single number, known as SpO2. This is a percentage measurement of haemoglobin linked to oxygen and for this reason is usually denoted using the symbol SpO2.
Measuring another vital sign: oximetry
Oxygen is largely transported by the haemoglobin molecules present in the red blood cells. It can be said without exaggeration that when the haemoglobin is very low, as in acute anaemia, a risk of instant death exists! In the reality of our organism, haemoglobin molecules cannot always transport their maximum load. On the basis of our state of health, SpO2 is at best 99%.
Haemoglobin and its ability to bond to blood oxygen
Each haemoglobin molecule is like an automobile with a load capacity of 4 passengers, represented by the molecules of oxygen entering the lung at each breath. If all the haemoglobin molecules could manage to load 4 oxygen molecules, they would be at maximum capacity: i.e. the SpO2 would be 100%. Normal SpO2 values are comprised between 95–99%. When an individual has respiratory problems due to lung, cardiac or neurological pathologies, this percentage falls, with values of < 95%: the entity of the reduction will indicate the gravity of the deficit.
A little bit of history
The Oximeter is an instrument that measures SpO2 in a simple and non-invasive way. Generally this instrument provides a measurement of the pulse frequency too, and is therefore also known as a Pulse Oximeter. The first prototype was devised in 1935 by the German physician Matthes, though the actual name “Oximeter” was coined by the American Physiologist Milikan. Following on from developments made during the Second World War, in 1974 Japanese engineer Takuo Aoyagi invented the first computerised Oximeter.
How the Oximeter functions
The Oximeter calculates the percentage of oxygenated haemoglobin (SpO2) by measuring the variations signalled in a two-wavelength light beam (red and infrared) crossing a part of the body characterised by a good arterial flow (such as the fingers or toes and the earlobes). While it goes without saying that the Oximeter should be used with patients having respiratory symptoms such as, for example, shortness of breath, its use is less obvious, especially, in apparentlyasymptomatic individuals when a respiratory, cardiac or neurological pathology is suspected. The Oximeter does not require any type of training, so even a patient can easily use it at home to monitor his or her state of health, the progress of treatment and the process of weaning from some procedures such as for example oxygen therapy.
Non-pneumological fields of application of Oximetry
Oximetry is by now indispensable in numerous “non-pneumological” medical procedures, such as endoscopic examinations, invasive procedures, ambulance transport and transfers within a hospital environment, emergency departments or first aid. Indeed, in anaesthesiological procedures, or deep sedation in surgical operations, Oximetry is a safety standard, and since its introduction there has been a 90% reduction in fatal accidents related to anaesthesia! When an individual has respiratory problems, SpO2 diminishes. Non-pneumological fields of application of Oximetry This phenomenon is called Desaturation and its entity indicates the gravity of the oxygen deficit and therefore of the respiratory failure too. It is known that at values of SpO2 ≤ 85 %, even the patient’s healthy brain endures cognitive, visual and electroencephalographic alterations.