When your medical team is discussing best care and management with you for any breathing difficulties you may have, they’ll be thinking not just about what your clinical classification was when you were diagnosed (such as SMA Type 1, 2, 3 or 4), but importantly which physical milestones are relevant for you now. For simplicity, they group people with SMA as:

  • non-sitters - those who are unable to sit
  • sitters - those who are able to sit but not walk
  • walkers - those who are able to walk 

They’re not the most user-friendly terms, but they’re used in the International Standards of Care for SMA (SoC) for those with 5qSMA (Types 1, 2, 3 or 4), which is the reference point for all medical professionals.   

Breathing problems may be common for anyone who's a ‘non-sitter’ (usually diagnosed with SMA Type 1) and anyone who’s a ‘sitter’, but they’re rare for anyone who’s a ‘walker’.

Why people may have breathing difficulties 

You may be very familiar with why some people have difficulties and what these can be, but if not, this recap may be helpful. 

When we breathe in, muscles called inspiratory muscles act as bellows to expand our lungs, enabling oxygen to be pulled in. The most important inspiratory muscle is the diaphragm – a dome-shaped muscle below the lungs. SMA causes the inspiratory muscles to be weakened and results in a decreased lung volume.

Breathing out the waste gas (carbon dioxide) from the lungs is known as expiration. This doesn’t need particularly strong muscles, but coughing does.

If you do have breathing problems, these are often due to having a weak cough and only being able to take in smaller breaths.

Everyone’s affected differently, but the main problems caused by weak breathing muscles are that:

  • It makes it difficult for you to cough and therefore clear mucous (secretions) from your lungs. 
  • Your lungs can’t get rid of enough of the waste gas produced by breathing - which includes carbon dioxide. When the levels of carbon dioxide in your blood are increased, this is known as ‘hypoventilation’.
  • It may make it difficult for you to take in enough oxygen while you’re asleep.

Care and Management

Chapter 6 Breathing (Respiratory and Pulmonary Care) in A Guide to the 2017 International Standards of Care for SMA (SoC) outlines what care and management is appropriate if you have breathing difficulties. If you have questions about this, a respiratory specialist is the best person to advise you.

Page last updated: July 2019