Shortness of breath has many different causes. For example, heart disease can cause breathlessness if your heart is unable to pump enough blood to supply oxygen to your body. If your brain, muscles, or other body organs do not get enough oxygen, a sense of breathlessness may occur.

Breathing difficulty may also be due to problems with the lungs, airways, or other health problems.

Problems with the lungs:

• Blood clot in the arteries of the lungs (pulmonary embolism)
• Swelling and mucus buildup in the smallest air passages in the lungs (bronchiolitis)
• Chronic obstructive pulmonary disease (COPD), such as chronic bronchitis or emphysema
• Pneumonia
• High blood pressure in the arteries of the lungs (pulmonary hypertension)
• Other lung disease

Problems with the airways leading to the lungs:

• Blockage of the air passages in your nose, mouth, or throat
• Choking on something stuck in the airways
• Swelling around the vocal cords (croup)
• Inflammation of the tissue (epiglottis) that covers the windpipe (epiglottitis)

Problems with the heart:

• Chest pain due to poor blood flow through the blood vessels of the heart (angina)
• Heart attack
• Heart defects from birth (congenital heart disease)
• Heart failure
• Heart rhythm disturbances (arrhythmias)

Other causes:

• Allergies (such as to mold, dander, or pollen)
• High altitudes where there is less oxygen in the air
• Compression of the chest wall
• Dust in the environment
• Emotional distress, such as anxiety
• Hiatal hernia (condition in which part of the stomach extends through an opening of the diaphragm into the chest) 
• Obesity
• Panic attacks

There is no standard definition for difficulty breathing. Some people feel breathless with only mild exercise (for example, climbing stairs), even though they don't have a medical condition. Others may have advanced lung disease, but may never feel short of breath.

Wheezing is one form of breathing difficulty in which you make a high-pitched sound when you breathe out.

Breathing difficulty may involve:

• Difficult breathing
• Uncomfortable breathing
• Feeling like you are not getting enough air

Sometimes, mild breathing difficulty may be normal and is not a cause for concern. A very stuffy nose is one example. Strenuous exercise, especially when you do not exercise often, is another example.

If breathing difficulty is new or is getting worse, it may be due to a serious problem. Though many causes are not dangerous and are easily treated, call your health care provider for any breathing difficulty.

If you are being treated for a long-term problem with your lungs or heart, follow your provider's directions to help with that problem.

The provider will examine you. You'll be asked about your medical history and symptoms. Questions may include how long you've had difficulty breathing and when it started. You may also be asked if anything worsens it and if you make grunting or wheezing sounds when breathing.

Tests that may be ordered include:

• Blood oxygen saturation (pulse oximetry)
• Blood tests (may include arterial blood gases)
• Chest x-ray
• CT scan of the chest
• ECG
• Echocardiogram
• Exercise testing
• Pulmonary function tests

If the breathing difficulty is severe, you may need to go to a hospital. You may receive medicines to treat the cause of breathing difficulty.

If your blood oxygen level is very low, you may need oxygen.

Go to the emergency room or call the local emergency number (such as 911) if:

• Breathing difficulty comes on suddenly or seriously interferes with your breathing
• Someone completely stops breathing

See your provider if any of the following occur with breathing difficulties:

• Chest discomfort, pain, or pressure. These are symptoms of angina.
• Fever
• Shortness of breath after only slight activity or while at rest
• Shortness of breath that wakes you up at night or requires you to sleep propped up to breathe
• Tightness in the throat or a barking, croupy cough
• You have breathed in or choked on an object (foreign object aspiration or ingestion)
• Wheezing