A person who is having mild difficulty breathing may:

• Breathe faster than normal.
• Have increased difficulty breathing with activity.
• Be able to speak in full sentences.

During an upper respiratory infection, swelling in the nasal passages and sinuses may cause some mild difficulty breathing. This is rarely serious, but it can be a nuisance.

Chest wall pain may cause more rapid, shallow breathing but does not cause true shortness of breath. The pain will subside as your cough improves. True shortness of breath is a feeling that you cannot get enough air or that you are smothering.

Examples of conditions that can cause shortness of breath include:

• Asthma, an inflammation and spasm in the tubes that carry air to the lungs (bronchial tubes).
• Chronic obstructive pulmonary disease (COPD), a condition that makes it difficult to breathe because air does not flow easily out of the lungs.
• Heart failure, a condition in which the lower chambers of the heart (ventricles) are not able to pump blood effectively.
• Pleural effusion, the buildup of fluid between the outer lining of the lungs and the inner lining of the chest cavity, which compresses lung tissue and hampers breathing.
• Pneumonia, an inflammation of the lungs caused by infection with bacteria or a virus.
• Pneumothorax, the buildup of air in the space (pleural space) between the lung and the chest wall, leading to a collapsed lung.
• Pulmonary embolism, sudden blockage of arterial blood flow within the lung.
• Shock, which may occur in response to a sudden illness or injury.