While most people don’t even think about breathing and how the human body does it, individuals with spinal muscular atrophy (SMA) don’t have that luxury.
The normal way the respiratory system functions is fairly simple: according to the SMA Foundation, the intercostal muscles (the ones that exist between the ribs) help the ribcage expand so when the lungs inflate they have space to do so. At the bottom of the ribcage is the diaphragm, which pulls the ribcage down so that there’s space for it to expand. For children with SMA, their respiratory system doesn’t work the same way, which affects their physical appearance.
No one truly breathes with their stomach, but you will hear the term stomach breathing quite often in reference to SMA.
SMA attacks the muscles, so the muscles between the ribs that are needed to breathe don’t function as they should. However, the diaphragm works just fine. This means that, while the chest wall won’t expand, the diaphragm will pull the ribcage down; instead of the chest expanding, the stomach area will, creating the illusion that the child is breathing from there, hence the term “stomach breathing.”
Due to mainly only using the diaphragm to breathe, the chest doesn’t expand which means the muscles in that area won’t strengthen at all. That being said, the lower ones will. This usually causes the child to have what’s commonly called a “bell-shaped chest,” which means the chest will be wider at the bottom than at the top. This will also cause a sunken chest, because the ribcage is going down and the sternum, the bone in the middle of the chest, is being pulled inwards.
It’s because of these differences in breathing behavior that respiratory care is so important for SMA patients. If you feel you need further information, talk to your medical team.
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