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Saturation determines the degree of saturation of arterial blood with oxygen. Red blood cells carry most of the oxygen by collecting it from the lungs and delivering it to all parts of the body. The body closely monitors the oxygen level in the blood to keep it within the specified range to ensure that there is enough oxygen for each cell’s needs. The level of saturation is an indicator of how well the body carries oxygen from the lungs to the cells and is important to our health.
Saturation is the percentage of oxyhemoglobin in the blood and is represented by arterial oxygen saturation (SaO2) and venous blood oxygen saturation (SvO2). Saturation is an important parameter in determining the oxygen content in the blood.
Each hemoglobin molecule contains four heme groups that can easily bind the molecular oxygen present in the blood. This means that a hemoglobin molecule can bind up to four oxygen molecules when transported in the blood. For adults, the normal SaO2 range is 95-100%. A value below 90% is considered low oxygen saturation and requires external oxygen supplementation. During aerobic metabolism, the body uses oxygen to convert glucose into pyruvic acid and make two ATP molecules. Blood oxygen content is determined by the oxygen-hemoglobin dissociation curve, which is a graph that expresses the ratio of saturated hemoglobin to oxygen partial pressure (PO2). The hemoglobin molecule becomes 100% oxygen-saturated (1,34 L of oxygen) with a PO2 of 100 mmHg.
After each oxygen molecule is bound, hemoglobin undergoes a conformational change that increases its affinity for the next oxygen molecule. Due to its high affinity for oxygen, each hemoglobin molecule becomes rapidly saturated with oxygen; thus the amount of free oxygen dissolved in the blood is only a very small fraction (2%) of the total oxygen present in the blood. For this reason, it is believed that the level of oxyhemoglobin is equal to the level of oxygen in the blood.
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Saturation is usually measured in two ways: arterial blood gas (ABG or Sa02) and pulse oximetry (Sp02).
ABG is usually only performed in a hospital setting, while pulse oximetry is performed in a variety of healthcare settings, including a doctor’s office.
Saturation and ABG
The ABG value refers to the level of oxygen and carbon dioxide in the blood flowing through the veins. A nurse takes blood from an artery, such as a radial artery in the wrist or a femoral artery in the groin. The sample is immediately analyzed by the machine or in the laboratory. The ABG value can give the clinician an idea of how effectively hemoglobin exchanges oxygen and carbon dioxide.
Saturation and pulse oximetry
Likewise, the pulse oximetry reading reflects the percentage of oxygen in the arterial blood. Unlike ABG, pulse oximetry is non-invasive. The test uses a sensor to read wavelengths reflected from blood. The probe is attached to a finger, ear lobe, or other place on the body. The results appear on the screen in seconds. Due to its simplicity, saturation levels can be easily monitored using wearable pulse oximetry devices, or oximeters. You can buy them at a pharmacy or online stores.
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Critical value of saturation – symptoms
Low blood oxygen levels can cause abnormal circulation and cause a wide variety of symptoms.
- Dyspnoea;
- Headaches;
- Anxiety;
- Dizziness;
- Fast breathing;
- Pain in the chest;
- Confusion;
- High blood pressure;
- Lack of coordination;
- Blurred vision;
- Feeling of euphoria;
- Fast heartbeat.
Blood disorders, circulation problems, and lung problems can prevent your body from absorbing or transporting enough oxygen. This, in turn, may lower the saturation value.
Examples of medical conditions that may affect the saturation value include:
- respiratory tract infections (e.g. cold, flu, COVID-19);
- chronic obstructive pulmonary disease (COPD) – a group of chronic lung diseases that make breathing difficult;
- asthma – a chronic lung disease that causes the airways to narrow;
- pneumothorax – partial or complete collapse of the lung;
- anemia – lack of healthy red blood cells;
- heart disease, a group of conditions that affect how the heart works;
- pulmonary embolism – when a blood clot causes a blockage in the pulmonary artery;
- congenital heart defects – a structural heart defect that occurs at birth;
- sleep apnea – which is associated with pauses in breathing during sleep;
- pulmonary fibrosis – scarring and damage to the lungs.
Some medications, including painkillers, may also affect the saturation value.
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Critical value of saturation – hypoxemia
With low saturation, we can talk about the so-called hypoxemia. Potential causes of hypoxemia include:
- less oxygen in the air we breathe (e.g. when flying in an airplane);
- conditions affecting breathing such as asthma and COPD;
- conditions affecting oxygen uptake such as pneumonia;
- anemia that causes lower hemoglobin levels;
- inhaling another substance, such as carbon monoxide or cyanide, which binds more strongly to hemoglobin than to oxygen.
See also: Poisoning with hydrogen cyanide and other cyanides
Critical value of saturation – cyanosis
Cyanosis is a pathological condition characterized by extremely low oxygen saturation. There are two types of cyanosis: central cyanosis and peripheral cyanosis. In central cyanosis, the oxygen saturation level drops below 85%, which causes a bluish tinge to appear all over the skin and the visible part of the mucosa.
In peripheral cyanosis, which often occurs due to increased oxygen uptake by peripheral tissues, the bluish tinge only appears on parts of the body such as the hands and feet. The most common causes of peripheral cyanosis are venous stasis, low cardiac output, or very low exposure to cold.
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Critical value of saturation – complications
The critical value of saturation may affect the oxygen concentration in the body’s tissues, including organs and muscles. This condition is called hypoxia. Cells can adapt to the lack of oxygen when the deficiency is mild. However, with larger deficiencies, cell damage can occur, followed by cell death.
Hypoxia is often caused by hypoxemia, but it can also occur when other causes appear.
- Not getting enough red blood cells. There aren’t enough red blood cells to carry oxygen to the tissues. Possible causes include heavy bleeding from an injury or sickle cell anemia.
- Insufficient blood flow. For example, a stroke occurs when the blood supply to a certain area of the brain is low, and a heart attack occurs when there is low blood supply to the heart muscle. Both lead to the death of cells and tissues.
- Tissues require even more oxygenated blood than can be supplied. Severe infections leading to sepsis can result in hypoxemia and ultimately organ failure.
Critical value of saturation – treatment
In general, an oxygen saturation level below 95% is considered abnormal and an oxygen saturation value below 90% is referred to as an emergency.
In such cases, oxygen therapy is needed. This is because the brain is the most susceptible organ to hypoxia, and brain cells can begin to die within five minutes of being deprived of oxygen. If hypoxia lasts longer, coma, seizures, and even brain death can occur.
It is very important to determine the cause of low oxygen saturation in order to correct the problem. In chronic diseases such as COPD and asthma, the underlying cause is usually low air exchange in the lungs and alveoli. In addition to oxygen therapy, steroids or bronchodilators (rescue inhalers) may be needed to open the airways.
In case of heart disease, insufficient blood flow can reduce oxygen supply. Drugs that improve heart function, such as beta blockers for heart failure or prescriptions for cardiac arrhythmias, can help improve oxygenation. With anemia, the blood supply to the tissues is reduced because there are not enough healthy red blood cells with hemoglobin to carry oxygen. Sometimes a red blood cell transfusion is necessary to increase the levels of healthy red blood cells.
Critical value of saturation – how to increase saturation?
There are several ways to naturally increase the saturation value:
Breathing fresh air. Opening windows or going for a walk can increase the amount of oxygen supplied to the body, which increases the overall level of saturation.
- Quit smoking. Just two to three weeks after quitting, your circulation will likely improve significantly. After one to nine months, the breathlessness decreases. Both of these aspects contribute to the body’s ability to take in more oxygen.
- Performing breathing exercises. Simple breathing exercises, such as pursed mouth breathing and deep abdominal breathing, can open the airways and increase the amount of oxygen in your blood.
- Physical activity. Daily exercise can improve the gas exchange capacity of the lungs and protect against hypoxemia. However, it is important to consult your doctor before beginning any exercise regimen or making changes to your daily exercise routine.
- Proper nutrition. A healthy and balanced diet can also help improve your blood’s oxygen saturation. Since iron deficiency is one of the main causes of low oxygen saturation, eating iron-rich foods such as meat, fish, beans, lentils, and cashews can help.
You can also use the aforementioned pulse oximeter to check the oxygen level in your blood and see if these natural ways to increase your oxygen intake are working for you.
However, keep in mind that if you are suffering from an illness (especially a serious illness such as pneumonia or carbon monoxide poisoning), these natural remedies may not be enough to raise your blood oxygen levels to an acceptable level. If symptoms of hypoxemia develop, go to the nearest hospital as soon as possible.
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