A person’s blood oxygen level is the amount of oxygen that is circulating in their blood. Red blood cells collect most of this oxygen from the lungs and carry it to different parts of the body. During an asthma exacerbation, or asthma attack, a person may have lower blood oxygen levels, as asthma can reduce the body’s capacity to take in oxygen.

By measuring their blood oxygen levels, a person can get an idea of how well their body distributes oxygen from the lungs to their cells. This can be useful because it helps someone closely monitor their respiratory health.

This article discusses how asthma affects a person’s blood oxygen levels. It also looks at normal oxygen levels in the blood, how to measure the levels of oxygen in the blood, and what to do if those levels are too low.

A person, who may have asthma, using a pulse oximeter to check their oxygen levels.Share on Pinterest
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Asthma is a long-term condition that affects a person’s airways. It can make breathing difficult and cause a person to wheeze.

According to an older 2013 article, acute exacerbations of asthma, or asthma attacks, can lead to reduced oxygen levels in the blood.

An older 2002 clinical review notes that asthma can cause airways in different parts of the lung to become occluded, which can result in impaired exchange of oxygen between the air sacs in the lung and blood flowing through the lungs. This means that less oxygen enters the bloodstream for circulation around the body.

A normal blood oxygen level for an adult without asthma is 75–100 millimeters of mercury (mm Hg).

If a doctor is using a pulse oximeter to measure the blood oxygen level (SpO₂), a normal level would read 95% or more, according to the Minnesota Department of Health.

Learn more about low and normal blood oxygen levels here.

If a person has asthma, they may have low oxygen levels during an asthma attack due to the impact the condition can have on the lungs. However, this is not always the case. A person can experience an asthma attack without it impacting the level of oxygen in their blood.

If a person believes that they are experiencing low oxygen levels, they should contact a medical professional as soon as possible.

Medical professionals consider low oxygen levels to be in the region of 65 mm Hg. This corresponds to an oxygen saturation level of 92% in both adults and children. This can cause a number of issues, so it is important that a person knows what to do if their oxygen levels become too low.

When a person’s blood oxygen levels are low, medical professionals refer to this as hypoxemia.

Having hypoxemia means that the body is unable to deliver the correct levels of oxygen to all of its cells, tissues, and organs. This can be a concern, as lower oxygen levels can cause complications in body tissues and organs.

Some common symptoms of hypoxemia include:

A pulse oximeter is a device that a person uses to measure oxygen levels in their blood. Pulse oximeters measure the percentage of hemoglobin that is saturated with oxygen.

To use a pulse oximeter, a person clips the device to their finger. A beam of light then passes through the finger to a detector that sits on the other side of the skin. While this happens, the device measures the estimated oxygen levels in the blood.

The device then shows the person their estimated oxygen saturation levels and heart rate on its digital display.

Should a person use a pulse oximeter to manage their asthma?

The Asthma and Allergy Foundation of America states that there are no data that demonstrate that monitoring oxygen levels with an oximeter will help a person manage their asthma.

Pulse oximeters allow people to measure their blood oxygen levels continuously. However, they can provide inaccurate readings, and they do not provide as much information on other gases, such as carbon dioxide, in the blood.

Pulse oximeters can be accurate within 2–4%. This means that the reading can be 2% or 4% lower or higher than the person’s actual oxygen levels.

A number of factors can reduce the accuracy of these readings, including:

  • nail varnish or nail polish
  • particular dyes that medical professionals use in other diagnostic tests
  • shivering, shaking, or other bodily motions
  • skin temperature
  • skin thickness
  • tobacco smoke

In addition, 2020 research found that a person’s skin pigmentation can affect the readings. The researchers noted that pulse oximetry fails to detect low oxygen saturation more often in Black people than in white people.

An arterial blood gas (ABG) test is another method that doctors may use to measure a person’s blood oxygen levels.

This test can also detect the levels of other gases in a person’s blood, as well as the blood’s pH.

To carry out an ABG test, a medical professional takes blood from a person’s artery. This is because blood that comes from an artery is oxygenated. They then analyze the blood and accurately measure the blood oxygen levels.

Asthma can be life threatening for a child, so it is very important that a person seeks medical attention if a child starts to show symptoms of asthma.

A medical professional will then be able to offer advice on the best methods available to manage the condition.

It is also vital that a person seeks immediate medical help if they experience oxygen deprivation. Symptoms of this can include:

A person’s blood carries oxygen from the lungs and around the body to all of the different tissues and organs.

A normal blood oxygen level is 75–100 mm Hg, which reads as approximately 95% or more using a pulse oximeter.

Due to asthma causing damage and irritation to the respiratory system, it can cause a person to have lower blood oxygen levels. If a person experiences oxygen saturation of 92% or lower, they should contact a medical professional as soon as possible.

A person may wish to measure their oxygen saturation with a pulse oximeter. However, these devices do sometimes give inaccurate readings.

If a person with asthma experiences headaches, shortness of breath, and confusion, they may have low blood oxygen levels. If this is the case, they should contact a medical professional.

It is also vital that a person seeks immediate medical help if they struggle to breathe, feel dizzy, and experience shortness of breath.