Oxygen Saturation: Normal Oxygen Level & Shortness of Breath

One of the most frequently asked questions about lung disease is also one of the most baffling: Why do people with COPD experience shortness of breath despite a normal oxygen level reading? What is normal oxygen saturation? Low oxygen saturation and a higher heart rate are common in COPD patients, so why would a person with an oxygen level of 95% still experience breathlessness? Because COPD seldom exists in a vacuum, we must look beyond the lungs to find the answer

COPD and Chronic Heart Failure

According to the American College of Cardiology, heart failure and COPD are common long-term health conditions that frequently co-exist. When you have both conditions, it’s often difficult to differentiate which is causing your symptoms. Because symptoms of both illnesses commonly overlap – and both frequently occur together – it is important for people with COPD who experience breathlessness with exertion, coughing during the night, or breathlessness and coughing spells during the night, to undergo a thorough physical examination to determine if the symptoms are related to COPD, heart failure, or both.^[1]

What is Heart Failure?

Heart failure occurs when the heart is no longer able to pump a sufficient amount of blood through the body. Similar to COPD, people with heart failure can be somewhat stable, or they can experience exacerbations (periods of time when their symptoms worsen). There are many conditions that can lead to heart failure, the most predominant being coronary artery disease.

When the heart is too weak to pump enough blood to the cells, tissues, and organs, every system in the body is affected: Muscles weaken, weight loss occurs, fatigue and breathlessness are common, and physical activity becomes increasingly difficult.^[1]

How Does Heart Failure affect Oxygen Saturation?

Oxygen saturation is a term used to define how much oxygen the hemoglobin in your blood is carrying. It is commonly measured by a pulse oximetry monitor, a non-invasive device that attaches to the end of your finger. When people with stable COPD (meaning they are not having an exacerbation) also have heart failure, it is not unusual for them to experience shortness of breath, yet have a normal oxygen level reading. In fact, people with both COPD and heart failure could have an oxygen level 96, which would normally be considered high oxygen levels for a COPD patient, and still experience shortness of breath. This is because, as the volume of blood pumped by the heart lessens, the oxygen saturation level is not immediately affected. However, the lower volume of blood being pumped means that your organs are getting less oxygen. Over time, lack of oxygen affects every organ in the body including the lungs, which may eventually lower oxygen saturation.^[1]

Skeletal Muscle Abnormalities

Rising from bed – getting dressed – taking a shower – going to work – we rely upon our skeletal muscles to perform all our daily activities. Skeletal muscles are found throughout the body. Their primary role is that of supporting the skeleton and voluntarily moving the bones. When our muscles are fit and well-conditioned, daily activities are a breeze; when our muscles fatigue easily from prolonged disuse, daily activities are far more challenging.

Although COPD primarily affects the lungs, skeletal muscle abnormalities are a secondary consequence of the disease. Shortness of breath and fatigue, which are common symptoms of COPD, often cause patients to limit their physical activity for fear of worsening breathlessness. The vicious cycle of prolonged inactivity, fatigue and increased breathlessness with exertion leads to decreased muscle fitness and weakness. Remaining immobile for long periods of time causes the skeletal muscles to slowly decrease in size and eventually atrophy, or waste.^[2]

How Do Skeletal Muscle Abnormalities affect Oxygen Saturation?

When your muscles are called upon to perform any type of physical task, they have to work harder, which increases their demand for oxygen; this is why exerting yourself increases your heart rate and breathing. In contrast, calling upon weak muscles to perform physical activity requires much more effort and high oxygen levels, leading to greater fatigue and breathlessness much faster, more so than if your muscles were fit. Take, for example, climbing 3 flights of stairs; even if you are moderately active, you are likely to experience some degree of breathlessness by the time you reach the top. Now imagine your muscles are extremely weak from inactivity; simply rising from a chair or walking across a room can lead to breathlessness.

Unlike shortness of breath directly related to lung impairment however, breathlessness caused by skeletal muscle abnormalities may not always correlate with oxygen saturation numbers. This means it is entirely possible to experience breathlessness while maintaining a normal O2 saturation reading, without seeing a drop in your oxygen saturation level at all. In fact, you may have an oxygen level 95 and still feel short of breath with any standard physical exertion.^[1]

Exercise: The Key to Breathlessness

The answer to breathlessness from COPD, heart failure and/or skeletal muscle dysfunction is exercise in order to maintain high oxygen levels. In fact, the American College of Cardiology reports that people who have COPD and heart failure together are prime candidates for exercise training. Moreover, skeletal muscle abnormalities can be completely reversed by participating in an exercise training program or a cardiopulmonary rehabilitation program.^[1]

Talk to your health care provider for more information about enrolling in cardiopulmonary rehab. If you are ready to start an exercise program on your own, consider reading How to Exercise with an O2 Concentrator

Frequently Asked Questions: Normal O2 Saturation & Breathlessness

Is oxygen level 95 a normal O2 saturation level?

There are a lot of factors when it comes to your normal oxygen saturation level, and if you have COPD, you might find that your normal O2 saturation levels are lower than the normal range. While a “normal” reading for a healthy person is typically between 100% and 95%, a person with COPD may maintain an oxygen level of 94. Talk to your doctor about what a normal oxygen level is for you, and ask about how to measure your normal O2 saturation at home. Whether you experience low oxygen saturation and high heart rate, or high oxygen levels with breathlessness, let your doctor know if you experience shortness of breath. It is especially important if you have normal O2 saturation levels as it may indicate the need for other interventions and treatment. 

What causes a low oxygen saturation and high heart rate?

There are several conditions and situations that can cause people to experience low oxygen saturation and a high heart rate. This can include people with lung diseases like COPD or pulmonary fibrosis, people with breathing conditions like asthma or bronchitis, people experiencing high altitudes and people with sleep apnea. Very often, if you have a condition that causes breathlessness, you will experience a lower oxygen saturation and higher heart rate as a result. However, do be aware that some conditions, like heart failure and skeletal muscle abnormalities, can combine with conditions like COPD to cause breathlessness without a low oxygen saturation level. 

Is an oxygen level 94 bad?

It is essential to know what is normal for you in order to answer this question accurately. For some people, an oxygen level 96 is fantastic, while for others, an oxygen level 94 can be quite worrisome. The answer is entirely dependent on your overall health. An oxygen level 94 might be considered low for someone in average health, or it can be in the upper levels for someone living with COPD. If you are concerned about your oxygen saturation, talk to your doctor about what your normal O2 sat should be. 

Does oxygen level affect heart rate?

Yes. If your oxygen saturation levels are low, your heart rate increases to help pump more blood through your lungs where it can be oxygenated. People who struggle with getting enough oxygen and maintain a lower normal O2 sat (say oxygen level 94), like those with COPD, asthma or other pulmonary disorder, often have a faster heart rate. Similarly, if you have high oxygen levels and always maintain an oxygen level 95 or oxygen level 96, your heart rate may rest a bit lower.

Author: Deborah Leader RN, BSN, PHN

REFERENCES

1. Jelic, Sanja MD, Le Jemtel, Thierry H. MD. Diagnostic Usefulness of B-Type Natriuretic Peptide and Functional Consequences of Muscle Alterations in COPD and Chronic Heart Failure. CHEST 2006; 130;1220-1230. DOI 10.1378/chest.130.4.1220. Diagnostic Usefulness of B-Type Natriuretic Peptide and Functional Consequences of Muscle Alterations in COPD and Chronic Heart Failure – CHEST (chestnet.org)
2. Sunita Mathur, Dina Brooks, and Celso R. F. Carvalho. Structural alterations of skeletal muscle in COPD. Front Physiol. 2014; 5: 104. Published online Mar 19, 2014. doi: 10.3389/fphys.2014.00104.

Additional Sources:

• https://www.verywellhealth.com/oxygen-saturation-and-shortness-of-breath-in-copd-914653