Factors affecting oxygen saturation

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Oxygen saturation is the body's ability, or more specifically the ability of the haemoglobin on the red blood cells, to carry oxygen. Your oxygen level can be measured with a device called a pulse oximeter, which measures the saturation of your haemoglobin or SpO2.

It can also be measured with a blood test called an arterial blood gas. This test determines the partial pressure of carbon dioxide as well as oxygen and your acid-base status, or pH and bicarbonate levels.

Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease or COPD can have a profound effect on the oxygen saturation level in your body. People with COPD suffer from chronic oxygen deficiency because the air sacs or alveoli can no longer accommodate inhaled oxygen. The alveoli either have collapsed or are plugged with mucus. Individuals with this disorder often end up using supplemental oxygen as the body can no longer breathe in and maintain an adequate oxygen saturation level.

Pulmonary Circulation

Several disorders can affect the circulation to and from your lungs, which affects your oxygen saturation level. A pulmonary embolism, which is a blockage or blood clot that has travelled to one or more sections of your pulmonary artery, can come from any part of your body due to a broken bone, surgery, disease, pulmonary hypertension or cor pulmonale. Heart disease or lung cancer also alters your pulmonary circulation, causing a decrease in your oxygen saturation level.

Smoke Inhalation

Firefighters and people who have been trapped in a fire can suffer airway and lung damage from smoke inhalation from burning wood that causes thick, acidic smoke. This smoke burns and destroys lung tissue. As the water used to put out the fire turns to a fine mist, it picks up particles and chemicals from the burning debris and carries it into the lungs as the person struggles to breathe. As lung tissue deteriorates, the alveoli can no longer accept oxygen, causing a severe drop in oxygen saturation levels.


Emphysema permanently alters the structure of the air sacs in the lungs. The disease breaks down the walls of the alveoli, causing each one to merge with another, forming fewer, larger alveoli. This damage reduces the surface area available to absorb oxygen and release carbon dioxide. The disease process alters the oxygen saturation level. The drop in oxygen causes you to become short of breath because you breathe harder and deeper as your body tries to bring in enough oxygen to feed your cells. This condition also causes cor pulmonale, an enlargement of the right side of the heart due to the increased work of breathing.