To figure out why you're feeling short of breath, you have to understand what makes you crave breathing in the first place. You might think it's a lack of oxygen, but in most cases, it's something else entirely. There are two parts to breathing:
- Moving air in and out of the lungs
- Moving oxygen and carbon dioxide back and forth between the bloodstream and the lungs
We get oxygen by inhaling oxygen-rich air into our lungs, where the oxygen is picked up by red blood cells in the bloodstream. When the body's tissues burn oxygen as part of their fuel, they create carbon dioxide as a waste product. We get rid of carbon dioxide when the same blood that's flowing through the lungs picking up oxygen drops off molecules of carbon dioxide.
We need some of each gas (oxygen and carbon dioxide are gases) in our blood to function properly, but we need to keep a balance. We keep quite a bit of extra oxygen in the blood, so a short term lack of oxygen isn't that big of a deal. We need that emergency reserve in case a bear decides to chase us through the cul de sac or we have to teach a teenager how to drive.
Carbon dioxide, on the other hand, builds up pretty fast and we need to get rid of it in a timely manner. In fact, it's the accumulation of carbon dioxide that makes you feel like you desperately need to inhale when you hold your breath.
Not having enough oxygen or having too much carbon dioxide can result in feeling short of breath. High school coaches are rather fond of running "wind sprints" until players are gasping for air, unable to talk. In fact, feeling "winded" is another way to say you're feeling short of breath. Besides the players needing more oxygen, all that exercise has caused them to have lots of carbon dioxide they have to get rid of.
First Cause of Shortness of Breath: Body Demands More Air
Creating a demand for more air than you're currently getting makes you feel short of breath. These are the most common causes of increased demand, either because you need to get rid of carbon dioxide or because your body needs more oxygen:
- exercise
- shock
- heart attack
- sepsis (severe infection)
When the body simply needs more air because of increased demand, there isn't too much we can do other than fix the demand (stop exercising, treat the shock or the heart attack). Supplemental oxygen is one way to do it, but there is evidence that adding more oxygen to the bloodstream than is natural -- when airflow isn't the problem -- may do more harm than good. Indeed, some studies showed heart attack patients doing worse rather than better when they got supplemental oxygen.
It's not always the demand for air that's causing the problem. Sometimes it's the supply.
Second Cause of Shortness of Breath: Too Little Airflow
Most of the time, when folks think of having difficulty breathing, they think of problems getting air into the lungs. Anything that restricts airflow deep into the lungs -- all the way into the small sacs (alveoli) -- gets in the way of moving oxygen into the bloodstream and moving carbon dioxide out of the bloodstream.
Certain diseases can cause restricted airflow, and these either cause constriction of the airways from swelling or inflammation, or congestion from fluid or mucus:
Illnesses aren't the only causes of restricted airflow. Moving air in and out of the lungs is a mechanical process, so injuring the structures of the lungs and airways could also restrict the amount of air that makes it through. Most of the injuries that can cause restricted airflow are injuries to the chest, head or neck:
- broken ribs or flail chest (a section of broken ribs)
- penetration wounds to the chest (gunshot wounds or stabbings)
- paralysis (usually from a spinal injury to the neck)
There are other mechanical causes that aren't always thought of as injuries:
- choking
- drowning
- collapsed lung (pneumothorax), which can be caused by a hard thump on the chest, a penetration wound or may even happen spontaneously as part of a weakened lung from a disease like COPD
For the last two types of causes, some patients might not actually feel short of breath. Instead, they might simply experience weakness or confusion. Because in these cases, the body doesn't always realize it's having any trouble at all.
Third Cause of Shortness of Breath: Trouble Transporting Oxygen in the Bloodstream
Some things can prevent the bloodstream from adequately carrying oxygen from the lungs to the cells of the body. There are two problems that happen fairly often:
- carbon monoxide poisoning, which blocks the ability of the red blood cells to hold onto the oxygen molecules
- anemia, a lack of red blood cells, which are needed to transport oxygen
Final Cause of Shortness of Breath: Lack of Oxygen in the Air
Sometimes, there's just nothing you can do to make things better. At high altitudes, the air is too thin to contain an adequate supply of oxygen for the body's needs. In a confined space with limited air, eventually the amount of oxygen and carbon dioxide in the air will match exactly with what the body is exhaling and the body won't be able to absorb oxygen or get rid of carbon dioxide.
Source:
Henry, Mark C., and Edward R. Stapleton. EMT Prehospital Care. 3rd Ed. 2004. Mosby/Jems
