Ive written about this before, but this is such an important topic; one that effects most chronic lungers and causes more suffering than any other respiratory symptom, that Ive decided to come out of blog retirement to write about it again.
Most of the information that Ive been able to find on the internet regarding air-trapping is way too technical for the average person to understand. Hopefully my explanations will make it a little less confusing. This post will also appear as a topic on my Asthma forum pages for those of you who would like to discuss the issue further.
In a nutshell the term “air-trapping” refers to air that, well … gets trapped in your lungs!
Basically what happens, is that a person with an obstructive lung disease (like asthma), inhales a volume of air, but cannot exhale it easily or completely. The resulting sensation is often perceived as a feeling of chest heaviness or breathlessness. This uncomfortable symptom can vary in intensity from mild to debilitating and usually lasts until the lungs decompress to their baseline state. In the most severe cases, as in severe emphysema, air- trapping tends to get progressively worse and the lungs never fully decompress.
The hallmark of Emphysema, COPD and Severe Asthma, air- trapping occurs when mucus and/or inflammation obstructs the inside of air passages preventing the inhaled air from being easily exhaled. The condition can also occur when the airways themselves loose their elasticity (their ability to recoil) and/ or through the loss of alveolar attachments that stint the alveoli open from the outside. This type of destruction of the airways is seen in both emphysema and in chronic severe asthma (the former usually caused by cigarette smoking).
To get a better understanding of how air becomes trapped in the lungs , it’s helpful to review what goes on during the normal breathing cycle. I think this animation by the folks at Interactive Medical does a superb job of depicting that.
The act of inspiration (the act of inhaling) is an active process. It requires the use of certain muscles (in this case the diaphragm) to make the process work. What happens, is that the diaphragm muscle(which is a dome shaped muscle in your abdomen), contracts and pulls down making room for the lungs to expand within the chest cavity. The expansion of the lungs creates a vacuum within them, allowing air to be drawn in. As the lungs fill with air, stretch receptors tell the brain when equilibrium has been reached and inspiration terminates.
Expiration is (or should be)totally passive. Under normal circumstance there are no muscles used during the act of expiration. The whole system works pretty much like an inflatable balloon. You have “work” to blow up the balloon, but to deflate it, you just let it go and the air escapes by itself. Ah, but if you have swollen airways or thick mucus in them, or if your balloon is made out of cardboard or stiff plastic instead of rubber, it then becomes much harder for that balloon to deflate on it’s own. People who have obstructive lung diseases have to actually work harder to breath, because they have to literally “push” or force the air out of their lungs to make room for the next breath. This requires the use accessory muscles that you wouldn’t normally use to breath, and that extra muscle expends more energy, which makes you more tired and even more short of breath.
It’s important to note, that while air-trapping is abnormal, there is always a small amount of air that remains in the lungs after you exhale completely… even if have totally healthy lungs. This is known as residual volume. Without this residual air, your lungs would collapse into themselves and you would not be able to overcome the resistance required to re-inflate them.
With the exception of drugs like Tiotropium ( Spiriva) or the more radical treatments like LVS surgery or airway stints to treat the more severe forms of air trapping, there are really very few options out there. Certain breathing and relaxation techniques can help minimize the symptoms by basically tricking the brain and reducing the associated anxiety, but the best practice is to prevent the condition from occurring in the first place ,or if it does, by preventing it from getting worse.
This of course is an oversimplification of how and why air trapping occurs, there are different types of air trapping and many other factors involved, but hopefully my explanation gives you a better idea of what’s actually going when you hear the term…”air trapping”
OK, back to my retirement…