In medicine, we term this dyspnoea. The conditions that lead to a person feeling breathless is very varied and this is not always easy to pinpoint one cause.
To understand this symptom a little more, we need to know how breathing is controlled.
The first step occurs at the brain. Here the signals from the part of the brain that controls the contractions and relaxations of the breathing muscles (chest wall and diaphragm muscles) are concurrently sent to the part of the brain that senses these movements. There are also special receptors in the arteries that can sense the lack of oxygen or an excess of carbon dioxide or acidic levels in the blood. At the same time there are also receptors in the airway and lungs which feedback to the brain.
Essentially, these receptors collect the information that determines how much breathing is needed and transmits this to the brain which in turn sends signals to the breathing muscles to work harder. When there is a perceived mismatch between the incoming signals and signals going to the muscles, a sensation of air hunger (need to breath more) is increased.
Are there special types of breathlessness (these are usually associated with cardiac disease)?
- Orthopnoea – sensation of breathlessness when lying flat , relieved by sitting or standing
- Paroxysmal nocturnal dyspnoea – sensation that wakes the patients from sleep usually after 1-2 hours of going into sleep and patient often needs to sit up
- Trepopnoea – occurs lying on one side as opposed to the other
- Bendopnoea – breathlessness when bending down (eg to tie shoe laces)
- Platypnoea – breathlessness on standing upright and better lying flat
What are the possible causes of dyspnoea?
- Heart disease
- Lung disease
- Neuromuscular disease – weakness of muscle or nerve disorder
- Metabolic disorders
- Problems with oxygen carrying capacity of blood ( eg anemia)
- Deconditioning (lack of physical stamina)
- Gastrointestinal disease
How to determine the cause?
Your doctor will conduct a thorough review of your symptoms and the triggers for these symptoms. Following this, a full physical examination will be done to assess possible causes.
After this an electrocardiogram, chest X -ray and blood test may be conducted to determine what the causes may be.
Heart diseases that can cause a patient to be short of breath include some of the following:
- Structural heart disease (problems with the heart valves, heart function, presence of congenital defects)
- Coronary artery disease (blockages of the heart arteries)
- Electrical issues with the heart (abnormal heart rhythms can limit exercise capacity)
- Heart muscle problems (cardiomyopathy or heart failure) – Reduced pump function of the heart
- Pulmonary hypertension (High lung pressures within the heart)
Some of the tests that your cardiologist may conduct could include:
- Transthoracic echocardiogram – a simple, non invasive ultrasound scan of the heart, this could quickly rule out structural heart disease, assess muscle function and pulmonary pressures
- Stress testing or Computed tomography which could be useful to assess the possibility of blockages in the heart
- More invasive testing may be done if needed. This includes a coronary angiogram or a right heart catheterization study
One of the tests that may be particularly useful to determine the causes of breathlessness could be a cardiopulmonary exercise stress test, especially if the causes of dyspnoea remain elusive after other tests.
This is a test that is done by firstly assessing the lung function of the patient. The patient is then asked to exercise on a bicycle or a treadmill. The test measures the oxygen consumption and carbon dioxide production, ventilatory efficiency, time to muscle fatigue ( anaerobic threshold), electrical and cardiac response to exercise. This can provide additive information to determine the contribution of dyspnoea from deconditioning, cardiovascular, respiratory or neuromuscular causes.