What your blood oxygen level shows
Your red blood cells are like vehicles. Each can carry up to four oxygen molecules across your body, getting them to places like your heart and brain. Your body’s vital systems need a normal percentage of oxygen inside your blood at all times, known as your oxygen saturation. However, sometimes your blood can get either too much or too little oxygen, and in these cases, there can be serious health consequences.
In these cases, monitoring your blood oxygen level can help determine if treatments are working, or if they should be adjusted.
Keep reading to learn where your blood oxygen level should be, what symptoms you may experience if your level is off, and what happens next.
Where your blood oxygen level should fall
A measurement of your blood oxygen is called your oxygen saturation level. In medical shorthand, you may hear it called a PaO2 when using a blood gas and an O2 sat (SpO2) when using a pulse ox. These guidelines will help you understand what your result might mean:
Normal Blood Oxygen Levels
Older adults typically have lower oxygen saturation levels than younger adults. For example, someone older than 70 years of age may have an oxygen saturation level of about 95%, which is an acceptable level.
It is important to note that the oxygen saturation level varies considerably based on a person’s state of health. Thus, it is important to understand both baseline readings and underlying physiology associated with certain conditions to interpret oxygen saturation levels and changes in these levels.
- People who are obese and/or have conditions such as lung and cardiovascular diseases, emphysema, chronic obstructive pulmonary disease, congenital heart disease and sleep apnea tend to have lower oxygen saturation levels.
- Smoking can influence the accuracy of pulse oximetry in which the the SpO2 is low or falsely high depending on whether hypercapnia is present. With hypercapnia, it is difficult for the pulse oximeter to differentiate oxygen in the blood from carbon monoxide (caused by smoking).
- Oxygen saturation levels may decrease slightly when a person is talking.
- Oxygen saturation may remain normal (e.g., 97% and higher) for people with anemia. However, this may not indicate adequate oxygenation because there are less hemoglobin to carry an adequate supply of oxygen for people who have anemia. The inadequate supply of oxygen may be more prominent during activity for people with anemia.
- Falsely low oxygen saturation levels may be associated with hypothermia, decreased peripheral perfusion, and cold extremities. In these cases, an ear lobe pulse oximeter device or arterial blood gases would provide a more accurate oxygen saturation level. However, arterial blood gases are usually only taken in critical care or emergency settings.
Points to Consider
For medical purposes, a normal blood oxygen saturation rate is often considered between 95% and 100%.In practice, the SpO2 range of 92–100% is generally acceptable for most clients. Some experts have suggested that a SpO2 level of at least 90% will prevent hypoxic tissue injury and ensure client safety (Beasley, et al., 2016).
Low Blood Oxygen Levels
The medical definition of a low blood oxygen rate is any percentage below 90% oxygen saturation. Oxygen saturation below 90% is very concerning and indicates an emergency. Call 911 immediately if you or someone you know experiences such a low blood oxygen level.
When Low Oxygen Saturation Affects Your Brain
By the time your oxygen saturation has fallen to between 80% and 85%, your brain may be affected by the lack of oxygen. You may also experience vision changes.
What happens if your oxygen level is too low
When your blood oxygen level goes outside the typical range, you may begin experiencing symptoms.
shortness of breath
The first visible symptoms of low blood oxygen, cyanosis causes a blue tinge to develop on your skin, particularly around your mouth and lips and beneath your fingernail matrix. This change occurs when your blood oxygen saturation reaches approximately 67%.
Cyanosis is considered an emergency. If you’re experiencing symptoms, you should seek immediate medical attention. Cyanosis can lead to respiratory failure, which can be life-threatening.
What causes blood oxygen levels to be low
Conditions that can negatively affect your blood oxygen level include:
COPD, including chronic bronchitis and emphysema
acute respiratory distress syndrome
congenital heart defects
These conditions may prevent your lungs from adequately inhaling oxygen-containing air and exhaling carbon dioxide. Likewise, blood disorders and problems with your circulatory system may prevent your blood from picking up oxygen and transporting it throughout your body.
Any of these problems or disorders can lead to declining oxygen saturation levels. As your oxygen levels fall, you may begin experiencing symptoms of hypoxemia.
People who smoke may have an inaccurately high pulse ox reading. Smoking causes carbon monoxide to build up in your blood. A pulse ox can’t tell the difference between this other type of gas and oxygen.
If you smoke and need to know your blood oxygen level, an ABG may be the only way to receive an accurate reading.
How to adjust your blood oxygen level
If your blood oxygen level is too low, you may need to boost your oxygen saturation. This is often done with supplemental oxygen.
Home supplemental oxygen is considered a medication, and your doctor must prescribe it. It’s important to follow your doctor’s specific advice on how home oxygen should be used to avoid complications. Your health insurance may cover the expense.
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