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Breathing & MND: an introduction

What you should know

  • Motor neurone disease causes the muscles you have control over to weaken - this can include the muscles involved in breathing.
  • A baseline measurement of your breathing function soon after diagnosis can be helpful to guide future treatment.
  • Respiratory muscle weakness usually develops gradually, but can occur suddenly.
  • Let your doctor or clinic know if you show signs of breathing problems (the list below may help).

About breathing

When you breathe in, your chest expands and air is pulled into your lungs. This air includes oxygen that your body needs for survival.

When you breathe out your chest contracts and air is pushed out of your lungs. This air includes carbon dioxide that your body no longer needs.

There are two main types of respiratory muscles involved in expanding and contracting your chest for breathing; the intercostal muscles, which run between and over the ribs and the diaphragm, which separates the rib cage from the abdomen.

A cough is a very forceful breath out. When you cough your abdominal muscles contract, your diaphragm tightens and air is forced out of your lungs.  Having an effective cough is important because it prevents food from entering your windpipe and helps you clear mucus and secretions.

Breathing with MND

Motor neurone disease causes the muscles you have control over to weaken, including the respiratory muscles. Though it often occurs gradually, sometimes respiratory muscle weakness can be the first sign of motor neurone disease and in some cases it can occur quite quickly.

Respiratory muscle weakness causes breathing to become more shallow than usual. Less air is drawn into the lungs so less oxygen is absorbed into the blood. It is also more difficult to breathe out the carbon dioxide that is produced by the body. Keeping the right balance of oxygen and carbon dioxide in the bloodstream is important as it plays an important role in how your body works.

During sleep your intercostal muscles contribute far less to your breathing. If your diaphragm is weak, it may not be able to help you breathe effectively when you are asleep. This can disrupt your sleep and contribute to problems with the balance of oxygen and carbon dioxide in your bloodstream.1,2

Changes that may result from respiratory muscle weakness

  • disturbed night sleep or loss of sleep
  • daytime sleepiness
  • morning headaches
  • increased fatigue
  • decreased appetite
  • impaired concentration or confusion
  • irritability and anxiety
  • quiet voice and fewer words per breath
  • shallow, faster breathing
  • reduced movement of the rib cage or abdominal muscles
  • excessive use of the muscles in the upper chest and neck
  • breathlessness (dyspnoea) even when at rest
  • breathlessness lying flat (orthopnoea)
  • weakened cough and sneeze

Learn more about breathing and MND

Finding out more about respiratory management

Talk to your doctor early about respiratory management. A baseline measurement of your breathing function, soon after diagnosis, provides details about your 'usual' breathing and can be helpful to inform future treatment.

If you notice changes to your breathing let your doctor or clinic know. There are effective ways to reduce discomfort caused by respiratory muscle weakness. The best strategies for you can only be determined after careful consideration of your individual situation. This may include support around your breathing, coughing and your ability to clear mucus and secretions. This is especially important if you are having issues with repeat lung infections.

Early identification and management of breathing issues is important so your respiratory function should be regularly assessed and monitored.1,2

The respiratory muscle function examination

A respiratory muscle function examination usually includes assessment of vital capacity, sniff nasal pressure, arterial blood gas measurement and several other tests. A baseline measurement of your respiratory function is recorded at your first visit. Follow-up examinations will show trends in your respiratory muscle function.

Vital capacity

You blow into a spirometer, which measures the strength of your breath when you breathe out. To do this, your lips need to make a seal around the spirometer mouthpiece. If you have weakness in the muscles controlling speech and swallowing, and cannot make a seal around the mouthpiece, you may be asked to wear a facemask for the test.

Arterial blood gases

Blood samples are taken from an artery, usually in the wrist. The levels of oxygen and carbon dioxide in your blood are measured.

Sniff nasal inspiratory pressure

A small tube is placed to seal the opening of one or both of your nostrils and you are asked to breathe air into your nose through the sealed tube. This measures the strength of your breath when you breathe in.

Other tests of respiratory muscle function

You may be asked to undergo other tests, such as overnight monitoring of breathing. Some monitoring of breathing can take place at home using a machine called an oximeter. However, sometimes you may need to stay overnight in hospital for this to take place.

Referral to other health professionals

Other health professionals such as the specialist respiratory nurse, physiotherapist, palliative care team, speech pathologist, occupational therapist, dietitian and general practitioner may also provide you with specific advice about particular strategies for respiratory management.

More information

Breathing & MND: what you can do

Breathing & MND: medications and non-invasive ventilation