Understanding Blood Oxygenation and Circulation

Almost every living organism on the face of this planet relies on the presence of oxygen to fuel their vital processes. In humans, the distribution of oxygen to the tissues is facilitated by the circulatory system.

Oxygen Transport

By assisting in the process called respiration, the blood provides the body cells an effective delivery and disposal system and helps maintain the normal function of cells. Oxygen inhaled by the person from the atmosphere is transported to the body’s tissues by doughnut-shaped red blood cells found in the blood. These red blood cells contain hemoglobin, a substance that takes up oxygen as blood passes through the lungs and releases it into the cells. In turn, it also picks up carbon dioxide for removal. Oxygenated blood is bright red because the hemoglobin portion of the red blood cell is bound with oxygen. Deoxygenated blood has a darker shade of red.

Our cells need a constant supply of energy to power their activities. Likewise, they also need oxygen and utilize it to release energy. When there is an imbalance or interruption in the supply of oxygen in the body, a person may develop conditions that could greatly affect his/her health.

A pulse oximeter measures oxygen saturation based on the light signals that are reflected by pulsating blood at the site of the sensor. It has both red and infrared LEDs as light emitters because oxygenated blood has a different absorption rate for these wavelengths. Inside the device, the red to infrared ratio is calculated and converted to an SpO2 value. Normally, the saturation of peripheral oxygen (SpO2) or the amount of oxygen dissolved in the blood is at around 95-100%. Values lower than 90% is called hypoxemia or a low oxygen level in the blood. This condition indicates that the body is not receiving enough oxygen, and the person requires immediate and further evaluation.