Shortness of breath, also known as dyspnea, is the sensation of difficult or labored breathing. It has many possible causes that can be roughly broken down by organ system. Shortness of breath can results most often from problems in the airway, lungs or heart. It may also be caused by problems in the blood or other systems.
Airway
Expansion of the chest wall causes air to pass through the mouth or nose and into the windpipe in the neck, known as the trachea. From here it passes into the chest and divides into tubes in the lungs to deliver the air. A blockage anywhere along this pathway will lead to inadequate delivery of oxygen to the lungs and therefore shortness of breath. It is not uncommon for children to be playing with something in the mouth and accidentally inhale it. Infections may also occlude the airway. For example, according to Family Practice Notebook, epiglottitis is the swelling of the epiglottis, a flap like structure separating the wind pipe from the throat, and is caused by a bacterial infection. Tumors or scarring in the neck or chest can also occlude the airway.
Lungs
According to FamilyDoctor.org, the website of the American Academy of Family Physicians, there are many possible causes of shortness of breath in the lungs. Chronic obstructive pulmonary disease or COPD, often caused by smoking, takes the form of bronchitis or emphysema. Bronchitis is narrowing of the airways and excessive phlegm. Emphysema is the breakdown of normal lung tissue. Other causes include viral and bacterial pneumonia, asthma, cancer, or a collapsed lung. Inherited disorders may affect only the lungs, or multiple organ systems including the lungs, such as cystic fibrosis.
Heart
Family Practice Notebook also notes heart conditions as a source of dyspnea. Heart problems can cause shortness of breath in a couple of different ways. The right side of the heart delivers blood to the lungs; the blood then returns to the heart on the left side and is pumped out to the rest of the body. A problem with the left side of the heart such as from a heart attack will cause blood and fluids to back up into the lungs, making it difficult to pass oxygen on to the blood. In addition, the heart will have trouble delivering the blood and its oxygen to the body, causing further shortness of breath.
Blood
The blood can be a primary cause of shortness of breath or signal a problem coming from elsewhere in the body, according to FamilyDoctor.org. Red blood cells in the blood carry the protein hemoglobin, responsible for oxygen transport. Low red blood counts, called anemia, can cause shortness of breath. Also low hemoglobin concentrations in the red blood cells or defects in the hemoglobin molecule may cause shortness of breath. In addition, increased levels of acid in the blood can cause shortness of breath. This can occur during kidney failure or uncontrolled diabetes. Another possibility is a blood clot traveling to the lung.
Other Causes
Some other causes of shortness of breath originating in the central nervous system or brain include anxiety, panic attacks and pain, according to Family Practice Notebook. Obesity may cause shortness of breath as well because the muscles of respiration will have to work harder with every breath. A disease affecting the nerves or muscles could also lead to labored breathing, such as polio.
