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Why do I get short of breath so easily?

As with chest pain, shortness of breath is a non-specific symptom that can be caused by many different diseases, such as coronary artery disease, emphysema, pneumonia, congestive heart failure, asthma, and of course, pulmonary hypertension. Just as we discussed for chest pain, different medical problems cause different types of sensations that people generally lump together as shortness of breath. The medical term for shortness of breath is "dyspnea," which means an uncomfortable sensation of breathing.

As one example, in individuals with asthma the breathlessness is often described as chest tightness. With pulmonary hypertension, most of the time, people do not feel chest tightness, but instead a sensation of having a hunger for more air or a sense that it is taking too much effort to breathe.

There are several reasons why you might feel short of breath, and one of the most important is that your heart may not be able to increase its output in order to keep up with your body's increasing demand for oxygen. The more you increase your physical activity (walking, etc.), the more oxygen you will need to get from the air and deliver, via the blood, to all the working cells in the body. In patients with pulmonary arterial hypertension, the cardiac output is often lower than it should be and the pumping mechanism of the heart (particularly on the right side) may not be strong enough to overcome the increased resistance of the thicker and constricted pulmonary arteries.

The sensation of shortness of breath may occur even before your oxygen level is too low. As you exert yourself and the heart tries to increase its output, the right ventricle has to work harder than normal to do this. This strain on the right ventricle is sensed as shortness of breath. We do not know exactly how your body senses this strain, but the signal may come from receptors that sense stretch in the pulmonary arteries. Those receptors may get activated by the increased efforts that the right ventricle is making to increase blood flow through the stiff pulmonary arteries.

One of the consequences of having a lower cardiac output than you should is that there isn't the normal matching of blood flow with air delivery (ventilation) in the lung. This mismatch results in lower oxygen levels, and one of the body's reactions is to raise the pulmonary arterial pressure even further – just the opposite of what you would want.

The direct consequence of this mismatch between ventilation and blood flow is that your oxygen level (measured by your doctor as either the oxygen saturation on your finger or by an arterial blood gas) may fall too low when you exert yourself. Both problems with getting enough oxygen into the blood from the lungs and problems with oxygen delivery to the body create a sensation of shortness of breath. Oxygen is delivered via the blood, and when blood flow to the body is diminished from the left ventricle (see Why I am getting lightheaded?), less oxygen may be delivered to the body.

In addition, in pulmonary hypertension, there is a problem with transferring oxygen from the air you breathe to the bloodstream. Normally, in the lungs, oxygen is transferred from air in the alveoli to the capillaries. In pulmonary hypertension there are fewer capillaries than normal, and thus less opportunity for oxygen to make it into the bloodstream.

Why is my breathing worse when I walk up the stairs?

Walking up stairs requires increased oxygen delivery mainly to muscles of the legs. As stated above, oxygen transfer in the lungs and oxygen delivery by the heart is decreased in pulmonary hypertension. When the body requires increased oxygen, for example while climbing stairs, neither the lungs nor the heart is able to respond (see Why am I getting lightheaded?). The brain interprets this decreased oxygen delivery to the body as shortness of breath.