Why Am I Short of Breath?

Few experiences are more frightening than not being able to breath. We give little thought to the dozen or so breaths we take each minute of our lives …until there is not enough. And then, If our supply of air is threatened for even a moment, we cannot think about anything else. 

Shortness of breath is one of the most common complaints of patients coming into our office for an evaluation and can have many causes.  Our job is first to find out the cause. Once we know this, we can focus on the proper treatment.

Most people with breathing discomfort will fall into one of two groups: those with a lung problem and those with a heart problem.

Lung: “The Bellows”

All living things move and grow and both require energy.  Food is taken in, digestion converts complex food materials to chemical fuel (usually glucose) .  The fuel is burned in the presence of oxygen to produce high-energy chemicals that can be used by run the machinery of life.  The by-product of this process is water and CO2. Respiration is the process of  getting oxygen into our bodies, transporting It to working tissue and then picking up and carrying away CO2.  Oxygen is absorbed by the hemoglobuin in our red blood cells as they move through the tiny capillaries in our lung.  The empty red blood cell pick up the waste C02 and carry it back to the lungs to be released with each exhalation into the atmosphere.

The lung has two parts:  the airways and the alveoli.  The airway begins as a single big pipe (the trachea) and then, like the branches of tree, becoming progressively smaller until at the end, less than 1 mm in size, they bud into a collection of balloon-like airsacks called the alveoli.  The alveoli are constructed of elastic fibers that stretch to fill up with air when we inspire and contract to expel the air when we breath out.

The smaller airways (bronchioles) are dynamic and can dilate or constrict to increase or decrease the flow of air.

The alveoli are surrounded by tiny capilaires filled with red blood cells that soak up the oxygen and drop off the CO2. 

Lung Diagram

Inspiration occurs by expanding the ribcage and flattening the diaphragm creating a vacuum and a rush of inflowing air. When the muscles of the ribcage are relaxed, the elastic alveoli sqeeze the air out.


The Heart and Blood Vessels: The Pump

The  right side of the heart recieves oxygen poor and CO2 rich blood from tissues and pumps it through the lung where the C02 is dropped off and oxygen picked up.  The oxygen rich blood fills the left side of the heart where it is pumped throughout the body.  

Breathing Sensors

When the tisses in our body are working hard, such as when we exercise,  we produce more CO2 and the blood becomes more accidic. Specialiszed sensors, located in the big arteries of the neck and chest as well as the brain monitor changes in the amount of oxygen, C02 and acid in the blood.  When these sensors sound the alarm, the muscles of the chest and the diaphram are stimulated causeing us to take deeper and more rapid breaths.  The heart is stimulated to beat faster and stronger.  The firing of these alarm sensors also stimulates our conscious centers, making us feel  uncomfortable short of breath”until the oxygen, C02 and acid levels return to normal.

Now that we have the basic physiology down, In my next post, I will review the things that can go wrong to make us feel short of breath.