Dyspnea is the medical term that is assigned to shortness of breath , it is an annoying sensation of lack of air, which is often the result of obstruction of the airways or of some disease that causes oxygen is not reaching suitable for the lungs and other organs.


The difficulty breathing must be differentiated from other respiratory disorders such as tachypnea (rapid breathing), which can occur for physiological reasons (such as fever, agitation and anxiety) or diseases (such as diabetic ketoacidosis and pneumonia), without being necessarily related to some respiratory failure.

How is dyspnea produced?

The smallest anatomical structure in the lung is the alveolus. In this small space, the exchange of oxygen and carbon dioxide that the body needs to live takes place. Normally, oxygen from ambient air enters the body and carbon dioxide (which reaches the lung from the pulmonary blood vessels) is released.

If there is any situation that prevents oxygen from entering the alveolus from the outside or if there is any condition that generates accumulation of carbon dioxide or low concentrations of oxygen within the body, it is said that there is respiratory failure.

What does the patient with dyspnea feel?

Respiratory failure leads to a compensatory response, both voluntary and involuntary, from the body. Involuntarily, tachycardia is generated (to pump more oxygen-rich blood into the lungs), the rate of respiration increases using muscles of the rib cage (to increase the times the alveolus exchanges carbon dioxide with oxygen), and redistribution occurs of the body’s blood, since it goes to the most important organs to carry oxygen (that is why the nails and lips turn purple, which is known as cyanosis).

The patient’s voluntary response to dyspnea consists of straining his chest muscles even more to increase the vigor of his breathing, he also takes more air through the nose (nasal flutter) and through the mouth (gasps).

According to the American Thoracic Society (Parshall 2012), when this compensatory response is made aware by the patient and generates discomfort, and even a feeling of anguish or near death, then it is called dyspnea .

This means that some patients may have cyanosis in their nails with rapid breathing in addition to tachycardia and deny that they have dyspnea at any given time. Therefore, this awareness or subjective sensation will be determined by environmental, social and psychological factors of the patient.

Depending on the cause of the dyspnea , these symptoms may be accompanied by sounds generated within the lung, but easily heard at a short distance, such as whistling or wheezing, gurgling, snoring, or rhonchi. It is important that if you have any of these symptoms you consult your doctor.

What are the possible causes of dyspnea?

As said, dyspnea occurs due to lack of oxygen at the level of the vital organs of the body or due to the accumulation of CO 2 , so it is important to clarify that difficulty in breathing is not only caused by respiratory problems , but can also be evidenced in diseases of other organs and systems. Some causes of dyspnea are:

  • Heart diseases such as myocardial ischemia, cardiac tamponade or heart failure: where blood is not properly pumped to the body. Likewise, the compression of large vessels that go towards the heart generates dyspnea , such as the presence of mediastinal masses that produce Superior Vena Cava Syndrome.
  • Severe anemia: where there are not enough red blood cells to carry oxygen to vital organs.
  • Neuromuscular disorders : as in neurodegenerative or autoimmune diseases (myasthenia, lateral amyotrophic disease), which sometimes affect the respiratory muscles preventing proper inspiration, they can also generate paralysis of the vocal cords and diaphragm.
  • Obesity: because the volume of the rib cage can compress the airways (which happens in Pickwick syndrome and obstructive sleep apnea).
  • Abdominal causes : increased pressure from the abdomen to the chest such as ascites, hernias or giant hernias, pregnancy in advanced stages. 

Respiratory problems:

  • Bronchospasm: in asthma, chronic obstructive pulmonary disease, severe allergic reactions and pulmonary fibrosis.
  • Pulmonary thromboembolism and pulmonary hypertension: due to increased pressure in the pulmonary artery and pulmonary circulation.
  • Pneumothorax: due to collapse of the lung with the presence of air in the pleural cavity.
  • In respiratory infections such as bronchitis and pneumonia.
  • Airway obstruction: as in allergic reactions (enlargement of the glottis and epiglottis secondary to angioedema), presence of foreign bodies within the airway, bronchoaspiration (inclusion of contents of the digestive tract within the airway), presence of tumors in the airway such as laryngeal tumors and bronchogenic carcinoma.
  • Pulmonary edema: due to the presence of fluid in the lungs due to pulmonary, cardiac or metabolic pathologies.

By Dr. Eric Jackson

Dr. Eric Jackson provides primary Internal Medicine care for men and women and treats patients with bone and mineral diseases, diabetes, heart conditions, and other chronic illnesses.He is a Washington University Bone Health Program physician and is a certified Bone Densitometrist. Dr. Avery is consistently recognized in "The Best Doctors in America" list.

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