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Monday, October 5, 2015

What patients need to know about oxygen levels

The following was originally published on April 3, 2015

Understanding Oxygen and Oxygen Levels

Oxygen is essential to a normal functioning body. The progression of COPD, and COPD flare-ups, may cause your oxygen levels to become low. So what does this mean to you? Here is all you need to know about oxygen and oxygen levels.

What is oxygen?

It’s an element with the symbol O. It makes up about 21 percent of air. When you inhale, it travels through your lungs to your bloodstream, and then travels to tissues, such as heart tissue. A cell on this tissue will use it to make energy needed for it to perform its work. Lack of oxygen may cause tissue damage, such as heart damage.

How are oxygen levels monitored?

There are two tests:
  1. Arterial Blood Gas (ABG). This involves an blood draw from your wrist or arm. Thankfully, this test doesn’t need to be done too often thanks to another, simpler test called...
  2. Pulse Oximetry. A probe is placed over your finger or earlobe. Since this is an easy test, it is often considered the fifth vital sign, and may be checked frequently.
What are oxygen levels?

They measure how efficient your lungs are at inhaling oxygen and transporting it into your bloodstream. The three most important are:
  1. SaO2. It's a percentage that shows how saturated your arterial blood is with oxygen. It's obtained from an ABG, so it's very accurate. Normal is 95-98%, although 90% or better is usually considered acceptable.
  2. PaO2. It's the partial pressure of arterial oxygen. It's obtained from an ABG, and is an accurate measure of oxygen in arterial blood. A normal range is 80-100, although 60 or better is usually considered acceptable. It's the same as SaO2, although it's estimated by pulse oximetry. A normal value is 95-98%, although 90% or better is usually considered acceptable. 
What are low oxygen levels?
  1. Hypoxemia. This is the term used when your PaO2 is less than 60 or your SaO2 and SpO2 are less than 90 percent. It means your blood oxygen level is low. Hypoxemia may lead to hypoxia.
  2. Hypoxia. This means your tissues aren’t getting enough oxygen. 
456-789 Rule. This explains why your doctor doesn’t always need an ABG to check your oxygen levels. Generally speaking, your SpO2 matches up with your PO2 as follows:
  • 90 percent SpO2 = 60 PO2 (this is your normal range, and usually no oxygen therapy is needed)
  • 80 percent SpO2 = 50 PO2 (this is your hypoxemic range, meaning oxygen therapy is needed)
  • 70 percent SpO2 = 40 PO2 (this is severe hypoxemia, immediate treatment is needed to prevent tissue damage and death)
What causes low oxygen levels? The natural progression of COPD may cause areas in your lungs where oxygen gets in but is blocked from getting to the bloodstream. This may be due to loss of lung tissue (emphysema) or airway obstruction (bronchitis). COPD flare-ups may exacerbate this problem.

How does your body respond to hypoxia? When your brain senses hypoxia, your blood vessels constrict and your heart pumps harder and faster, sending blood in search of more oxygen. Your body shunts freshly oxygenated blood away from fingertips, toes and lips in favor of vital organs, such as your heart.

. When your oxygen levels are low, your body will let you know. Common symptoms include a bluish tinge to your fingertips, toes and lips (cyanosis), rapid heartbeat, sweating, confusion, and feeling short of breath or winded.

Long-Term Consequences. Hypoxemia with COPD may become chronic, meaning it’s always there and your body gets used to it. This may mean that the blood vessels in your lungs are chronically constricted, forcing your heart to work extra hard to pump blood through your lungs. Over time, this causes your heart to become enlarged (hypertrophy). This makes it a weaker pump, and may lead to heart failure.

. Your doctor will usually recommend the lowest amount of oxygen needed to keep your PaO2 at safe levels, which is usually 60 or better. So this means an SpO2 of about 90 percent is the goal, although sometimes 88 percent is acceptable. Medicine like corticosteroids and albuterol may help reduce inflammation and open airways.

Be Compliant. Oxygen is essential to life. Making sure your oxygen levels stay at safe levels is essential to living well with COPD. Work with your doctor, follow your COPD Action Plan, pay attention to what your body is telling you, and use your oxygen therapy as prescribed (if prescribed).

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