Oxygen saturation is a measure of how much oxygen is in your blood. Your organs and tissues need oxygen to work. Oxygen can "hitch a ride" in your red blood cells and travel through the bloodstream to get where it needs to go in your body. Show For most healthy adults, a normal oxygen saturation level is between 95% and 100%. An "O2 sat" level below this range requires medical attention because it means your body isn't getting enough oxygen. This article covers conditions that affect the amount of oxygen in your blood and the complications of having low oxygen saturation. You will also learn how to measure your blood oxygen levels and when to seek treatment. How Blood Gets OxygenatedTo understand how blood gets saturated with oxygen, you have to know about the air sacs in the lungs called alveoli. There are millions of these microscopic air sacs in the lungs. They exchange oxygen and carbon dioxide molecules to-and-from the bloodstream. As oxygen molecules pass through the alveoli, they bind to a substance in the blood called hemoglobin. Oxygen "hitches a ride" on the hemoglobin as it circulates until it gets dropped off to the body's tissues. Then, hemoglobin picks up carbon dioxide from the tissues and transports it back to the alveoli. Once there, the cycle can begin all over again. The level of oxygen in your blood depends on several factors:
Most of the time, hemoglobin contains enough oxygen to meet the body's needs. However, some diseases reduce hemoglobin's ability to bind to oxygen. Each one of your blood cells contains around 270 million molecules of hemoglobin. Any health condition that limits your body's ability to produce red blood cells can result in low hemoglobin levels, which in turn limits the amount of oxygen that can saturate your blood. Conditions That Affect Oxygen SaturationBlood disorders, problems with circulation, and lung issues can prevent your body from absorbing or transporting enough oxygen. When this happens, it can lower your blood's oxygen saturation level. Examples of conditions that can affect your oxygen saturation include:
How to Measure Your Blood Oxygen LevelsOxygen saturation is measured in one of two ways: an arterial blood gas test (ABG or Sa02) or pulse oximetry (Sp02). ABG is usually only done in a hospital, while pulse oximetry can be done in other healthcare settings (like a provider's office) and even at home. ABGAn ABG value refers to the levels of oxygen and carbon dioxide in blood running through your veins. During an ABG, a nurse or lab technician draws blood from an artery, such as the radial artery in the wrist or the femoral artery in the groin. The sample is immediately analyzed by a machine or in a lab. Your ABG value can give your healthcare provider a sense of how efficiently the hemoglobin in your blood exchanges oxygen and carbon dioxide. Pulse OximetryA pulse oximetry reading reflects the percentage of oxygen found in arterial blood. Unlike the ABG test, pulse oximetry does not involve a needle (non-invasive). Instead, the test uses a sensor to read wavelengths reflected from the blood. The probe is attached to your finger, earlobe, or another place on the body. A pulse oximeter can give results on a screen in just a few seconds. People can monitor their oxygen saturation levels using wearable pulse oximetry devices—some smartwatches even have this feature. You can also buy a pulse oximetry device at your local pharmacy or online.
What Causes Decreased Oxygen Saturation?A drop in oxygen saturation in the blood is called hypoxemia. It can be caused by:
How to Raise Blood Oxygen FastIf your O2 saturation level is low, you need to call your provider. If it's very low, you might need to seek emergency medical care. You can also take a few steps right away to try to increase your blood oxygen levels:
Complications of Low Oxygen SaturationLow oxygen saturation in the blood can mean there's less oxygen in the body's tissues, including the organs and muscles. When this happens, it's called hypoxia. Your cells can adapt to a lack of oxygen when the deficiency is small. However, with larger deficiencies, cell damage and cell death can happen. Hypoxia usually happens because there is not enough oxygen in the blood (hypoxemia). However, it can also happen when:
Treating Low Oxygen SaturationGenerally speaking, an oxygen saturation level below 95% is considered abnormal. An O2 sat below 90% is an emergency. If someone's oxygen saturation is dangerously low, they will need oxygen therapy—sometimes urgently. The brain is the most susceptible organ to hypoxia. Brain cells can begin to die within five minutes of oxygen deprivation. If hypoxia lasts longer, it can lead to coma, seizures, and brain death. It is very important to find out the cause of low oxygen saturation so the problem can be fixed. For example, with chronic conditions such as COPD and asthma, the cause of hypoxia is usually low air exchange in the lungs and alveoli. In addition to oxygen therapy, steroids or rescue inhalers (bronchodilators) might be needed to open the airways. In circulatory conditions like heart disease, inadequate blood flow reduces oxygen delivery. In this case, medications that improve heart function, such as beta-blockers for heart failure or prescription medications to treat heart 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 a person's level of healthy red blood cells. Summary Oxygen saturation is the measure of how much oxygen is traveling through your body in your red blood cells. Normal oxygen saturation for healthy adults is usually between 95% and 100%. If you have a chronic health condition that affects your lungs, blood, or circulation, regularly tracking your oxygen saturation is important. An O2 sat level below 95% is not normal. A level under 90% requires emergency care. Frequently Asked Questions
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