The muscle weakness caused by SMA can affect the muscles for breathing. Breathing (respiratory) problems may be common for teenagers who are unable to sit without support (usually diagnosed with SMA Type 1) and teenagers who are able to sit but not walk. They are rare for teenagers who are able to walk.

What happens and why?

When we breathe in our inspiratory muscles act as bellows to expand our lungs and pull in oxygen. The most important inspiratory muscle is the diaphragm. This is a dome-shaped muscle below the lungs. SMA causes the weakens the inspiratory muscles and decreases lung volume.

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

If you have breathing problems, it is often due to having a weak cough and only being able to take in smaller breaths. Everyone is affected differently. But weak breathing muscles can:

• Make it difficult for you to cough and clear mucus (secretions) from your lungs
• Mean your lungs can’t get rid of enough of the waste gas produced by breathing. This includes carbon dioxide. When the levels of carbon dioxide in your blood are increased, this is known as ‘hypoventilation’.
• Make it difficult for you to take in enough oxygen while you are asleep.

The SoC recommend that children and teenagers who are ‘sitters’ or ‘non-sitters’ should have a physical examination to check their breathing at least once every six months. At these appointments a spirometer machine is used to measure the strength of a person’s cough.

If you have trouble sleeping at night, or have headaches, this may mean you are not breathing well at night. If so, you should have an overnight sleep study. This may be at home with a small clip on your finger. This measures and records levels of oxygen in your blood. If it is in hospital, small sensors are attached to your face, head, arm and chest. They monitor you overnight. You usually also have a blood test.

All these tests help the doctors, you and your parents decide on the best options for managing your day-to-day breathing.

If you see a respiratory specialist, you can ask them questions about anything you don’t understand or that worries you. If you don’t have a respiratory specialist and are worried about your breathing, talk to your parents and healthcare team about a referral to one.

There are different ways to help manage breathing problems. This depends on what your team assess is right for you.

If you have a weak cough, you will know how difficult it is to clear mucus and other secretions from your lungs. This makes you more vulnerable to chest infections. Even if your breathing is usually fine, you may struggle to deal with chest infections. You may need additional ways to help you get over them.

Options that you may already use or that your team may discuss with you include:

• Chest physiotherapy to keep you comfortable and help clear secretions from your chest. Anyone caring for you would be trained to do this. You would all be advised how often is best for you.
• Cough assist is the name often given to a mechanical insufflator – exsufflator machine. This helps to clear secretions from your lungs. If it is something that would help you, you may be taught how and when to use it yourself. Anyone caring for you would also be trained.

This webinar explains the basics of cough assist and what it is like to use:

Recorded: November 2020

• A suction machine helps remove any excess secretions. Anyone caring for you would be trained to do this. You would all be advised how often is best for you.
• Non-invasive ventilation (NIV), is a machine with a mask providing gentle pressure to breathe against. This helps to keep your lungs inflated for longer. It can help you get rid of carbon dioxide and to take in more oxygen. This makes breathing easier. The mask is individually fitted for you by a respiratory specialist. When your breathing triggers the ventilator, it delivers a supported breath in. As you start to breathe out, the machine cycles into exhalation. This allows you to breathe out normally. BiPAP is one example of an NIV machine.
• Medication (mucolytics) can be used to break down secretions. They are not recommended for long term use.
• Antibiotics are not recommended by the SoC as a way of trying to prevent chest infections (prophylactic use). But the medical team will have a ‘low warning’ threshold for when you should start them.