It is possible to feel short of breath even when oxygen levels are normal. There are a few potential causes for this disconnect between symptoms and oxygen saturation readings.
What is shortness of breath?
Shortness of breath, also called dyspnea, refers to difficult or uncomfortable breathing. A person may feel like they cannot get enough air. Shortness of breath has many possible causes, ranging from temporary conditions like anxiety to serious medical issues like heart failure or lung disease.
Some common causes of shortness of breath include:
- Anxiety or panic attacks
- Asthma
- Chronic obstructive pulmonary disease (COPD)
- Pneumonia
- Pulmonary edema
- Heart failure
- Anemia
- Obesity
In mild cases, shortness of breath may simply feel like needing to take deeper breaths. More severe shortness of breath can be frightening or make it difficult to complete daily activities.
What are normal oxygen levels?
Oxygen saturation indicates the percentage of red blood cells filled with oxygen. Normal oxygen saturation levels are:
- 95-100% while breathing room air at sea level
- 90% or higher under most conditions
- 88% or higher for patients with chronic lung disease
Oxygen levels are usually measured by a small device called a pulse oximeter. This painless test shines light through the fingertip to determine oxygen saturation.
Why can you feel short of breath with normal oxygen levels?
There are a few reasons why someone may feel short of breath even if their oxygen saturation is within the normal range:
1. The cause is unrelated to oxygen levels
Some common causes of shortness of breath like anxiety, poor fitness, and obesity do not actually affect the amount of oxygen in the blood. So oxygen levels can still read as normal.
2. Ventilation/perfusion mismatch
Even if enough oxygen is circulating in the bloodstream overall, parts of the lungs may not be ventilated well enough to allow optimal oxygen absorption. This is called a ventilation/perfusion mismatch. The body senses this local mismatch and triggers sensations of shortness of breath. But pulse oximetry measures oxygen levels in the entire circulatory system, which can remain in the normal range.
3. Hypoventilation
Some lung diseases like COPD cause the respiratory muscles to work inefficiently. As a result, the body fails to take deep enough breaths to properly eliminate carbon dioxide. This hypoventilation allows carbon dioxide levels to build up, which triggers shortness of breath. But oxygen levels may remain normal if there is no separate issue with oxygen exchange in the lungs.
4. Delayed detection
Pulse oximetry has a brief lag in detecting drops in oxygen levels. So in acute situations like an asthma attack or pulmonary embolism, a person may start feeling short of breath before the oxygen saturation falls low enough to register as abnormal. Once the oxygen stats drop significantly, they would align with the sensation of shortness of breath.
When to see a doctor
In general, see a doctor for shortness of breath that arises suddenly, worsens, or occurs with other symptoms like chest pain, lightheadedness, or coughing up blood. Even if oxygen levels are normal, unexplained or worsening shortness of breath warrants medical evaluation. Call 911 or go to an emergency room immediately for severe shortness of breath.
Shortness of breath paired with normal oxygen saturation suggests one of the following:
- Anxiety or panic attack
- Deconditioning
- Obesity
- COPD exacerbation
- Other lung disease like pulmonary fibrosis or sarcoidosis
- Early stages of an acute event like pulmonary embolism or pneumonia
- Heart failure
Testing is needed to determine the cause and guide appropriate treatment. Potential tests may include:
- Chest x-ray
- Pulmonary function tests
- CT scan of the chest
- Echocardiogram
- Blood tests
- Electrocardiogram
- Exercise stress test
- Ventilation/perfusion scan
The results can identify any lung abnormalities, heart problems, blood clots in the lungs, or other causes that require specific treatment.
When shortness of breath needs immediate treatment
In some cases, shortness of breath requires emergency medical care. Go to an emergency room or call 911 (or the local emergency number) right away for:
- Sudden, severe shortness of breath
- Shortness of breath with chest pain
- Coughing up blood
- Wheezing or high-pitched noisy breathing
- Blue tinge to lips or fingertips
- Feeling like you are about to pass out
- Oxygen levels below 92%
These signs could indicate a potentially life-threatening cause needing immediate treatment, such as:
- Heart attack
- Pulmonary embolism (blood clot in lung)
- Pneumonia
- Collapsed lung
- Asthma attack
- COPD exacerbation
Emergency medical providers can evaluate the cause and provide oxygen or other breathing treatments if needed. Prompt care is crucial for preventing severe complications.
When to call 911 for shortness of breath
Specific circumstances that require calling 911 include:
- New, sudden onset of severe shortness of breath
- Inability to speak in full sentences due to shortness of breath
- Chest pain along with difficulty breathing
- Fainting or feeling like you will faint
- Coughing up blood
- High fever with shortness of breath
- Wheezing that worsens despite using an inhaler
- Blue color in lips or fingers
- Feeling confused or delirious
In these situations, minutes matter. Calling 911 can save a life by providing emergency oxygen, prompt treatment for blood clots, heart attack care, and other lifesaving interventions.
Managing chronic shortness of breath
For people with chronic lung conditions like COPD or pulmonary fibrosis, ongoing shortness of breath is common. To help manage chronic shortness of breath:
- Use prescribed inhalers correctly
- Quit smoking
- Practice pursed lip breathing exercises
- Stay active with a pulmonary rehabilitation program
- Use supplemental oxygen if prescribed
- Get recommended vaccinations like the flu shot and pneumonia vaccine
- Avoid environments that aggravate symptoms
- Learn how to pace activities and conserve energy
Report any worsening shortness of breath to your doctor right away, as it could signal an exacerbation needing prompt medical treatment.
Conclusion
Experiencing shortness of breath with normal oxygen levels can be confusing. But there are some logical reasons this disconnect can occur. Causes like anxiety, poor fitness, hypoventilation, or ventilation/perfusion mismatch may trigger shortness of breath without substantially impacting overall oxygen saturation.
In other cases, rapidly evolving medical emergencies like heart attack or pulmonary embolism may cause shortness of breath to start before oxygen levels drop low enough to register as abnormal on a pulse oximeter reading. Regardless of the cause, new, unexplained, or worsening shortness of breath warrants prompt medical evaluation.
Monitoring oxygenation and paying attention to associated symptoms provides important clues. Most cases of shortness of breath can be successfully managed by identifying and treating the underlying cause. With proper care, even chronic shortness of breath can often be well controlled, allowing people to remain active.
Example data tables
| Cause | Description | Symptoms |
|---|---|---|
| Anxiety or panic attacks | Feeling of breathlessness due to anxiety rather than an underlying physical condition | Associated nervousness, hyperventilation, tight chest, tingling, dizziness |
| Asthma | Chronic inflammatory lung disease causing airway narrowing and obstruction | Shortness of breath, coughing, wheezing, chest tightness |
| COPD | Chronic lung disease including emphysema and chronic bronchitis | Ongoing shortness of breath, wheezing, decreased exercise tolerance |
| Age | Normal Oxygen Saturation Range |
|---|---|
| 0-1 month | 95-100% |
| 1-12 months | 95-100% |
| 1-5 years | 95-100% |
| 6-12 years | 95-100% |
| Teens & Adults | 95-100% |