Oxygen is drawn into the body from the atmosphere by breathing. Each lung is inundated by an estimate of 300 million alveoli, which are cocooned by numerous blood capillaries. Alveolar walls and capillary walls are extremely thin, this makes them permeable, therefore, oxygen passing into the alveoli immediately diffuses into the blood capillaries – the process takes up only .25 seconds in an adult at rest.
The bulk of oxygen that diffuses into the blood binds itself to hemoglobin molecules that are found in red blood cells creating oxyhemoglobin. The smaller bulk of the oxygen that is left over dissolves into the blood plasma. Blood that is rich in oxygen (arterial blood) then flows through pulmonary veins, into the left atrium and left ventricle, and finally circulates throughout the entire body’s organs and their cells.
Carbon Dioxide, which is a byproduct of cell metabolism, dissolves in the blood and is circulated back to the lungs where it is released as fresh oxygen attaches itself to hemoglobin and the cycle is replicated and repeated over and over again.
The total amount of oxygen that is transported around the body is shaped by many factors: the lung factor which is the degree to which hemoglobin binds to oxygen, the anemic factor which is the hemoglobin concentration and the cardiac factor which is essentially the cardiac output.
Oxygen saturation levels are an indicator of oxygen transportation in the body and point to whether oxygen is being supplied to the body, especially to the lungs in sufficient amounts.
What is SPO2
The pulse oximeter makes use of two frequencies of light (red and infrared) in order to gauge the percentage (%) of hemoglobin present in the blood that is dense with oxygen. The percentage calculated is called Blood Oxygen Saturation or SPO2.
Hemoglobin molecules with attached oxygen molecules (Hbo2) absorb a different level of red and infrared light in comparison to hemoglobin molecules, which don’t have any oxygen molecule, attached (Hg). The difference range between absorption using an infrared light and a red light is used to gauge the SpO2 percentage.
Each hemoglobin molecule can carry a load of four oxygen atoms and SPO2 is the sum percentage of hemoglobin molecules, which are oxygen-rich. Pulse oximeters also measure and display the pulse rate while measuring the SPO2 levels.
SpO2 readings are recorded in percentages. Normal levels of SpO2 rest between range of 95-100%.
Blood Oxygen Saturation levels can be read as follows…