Key definitions

There can be a lot of new words when learning about any topic. Here are some of the common terms you’ll hear and read across the myBreathing website, with a simple explanation. Click on the boxes at the top to filter the terms/words by group.

Alert wristband

An alert wristband warns healthcare staff of important information about your care needs. In the UK the MND Association supplies an MND alert wristband. This also warns health care staff to be cautious about giving oxygen. Giving oxygen therapy can be dangerous in MND/ALS.

You can order one from the MND Connect Helpline on 0800 802 6262 or visit here for more information.

BiPAP ventilation

This is another, more clinical term for non-invasive ventilation (NIV).

BiPAP stands for ‘Bi-level Positive Airway Pressure’. ‘Bi-level’ means it senses and follows the two phases of your breath, as you breath in and then out.

‘Positive airway pressure’ means the air is pressured just enough to gently open your airways and lungs, getting more air in.

BiPAP machine

Another name for an NIV machine. It refers to the type of breathing support, known clinically as BiPAP ventilation – ‘Bi-level Positive Airways pressure’ (see definition).

Blood gas level

Blood gas levels are a way of measuring how much oxygen and carbon dioxide there is in your blood. This helps to see changes to your breathing.

MND/ALS can affect the balance of your gas exchange – taking oxygen in and breathing waste carbon dioxide out. Increases in carbon dioxide levels causes various symptoms, including tiredness and headaches.

Breathing or respiratory muscles

These are the muscles in the chest and abdomen that help us to breathe air into the lungs. The main muscle is the diaphragm (below the lungs). Muscles between the ribs also support breathing. MND/ALS can lead to these muscles becoming weaker over time.

Breath stacking

Breath stacking is a technique to support better coughing. MND/ALS weakens the breathing muscles which has various effects, including reducing the effectiveness of coughing. To cough you need to expel a large volume of air suddenly under high pressure.

Breath stacking is a technique that can be taught to you by a respiratory physiotherapist. It involves taking in a breath, holding it in, adding more air on top and repeating (‘stacking’ the breaths) – then breathing out suddenly. This cycle is repeated a few times in a row. It can help bring up mucus from deeper inside the lungs.

Breath stacking can also be done with a lung volume recruitment bag (LVR). This looks like a firm ballon with a face mask attached. This supports breathing in.

Carbon dioxide

Carbon dioxide is a gas that is found naturally in the air.  It is a very small percentage of the air around us (0.04%). It used by plants and trees to make energy from the sun.

Humans breathe in oxygen which is transported via our blood to our cells. Cells use oxygen to release and use the energy from our food. Carbon dioxide is a waste product from this process. It is carried by the blood, back to the lungs where we breathe it back out.

It is important that we breathe out enough of the waste carbon dioxide. If it builds up in the body this can have bad effects. At lower levels it can cause fatigue and headaches. At higher levels it can cause more serious problems. Ventilation helps to breathe out more carbon dioxide.

Chest infection

A chest infection is any kind of infection in your lungs or airways. It can cause increased coughing and production of green, yellow or dark mucus. Pneumonia is a severe chest infection.

People with MND/ALS are more prone to catching chest infections. This is because of the reduced ability to cough, due to muscle weakness. It may be harder to recover as well. Try to avoid people with coughs and colds.

Cough assist

Cough assist is a machine that supports effective coughing. It has a pump, which pushes air briskly down a tube to a face mask. The mask is held on the face by hand for a few seconds and then removed.

The rush of air simulates the action of coughing. It helps to bring up mucus from the lungs.

Dependency on ventilation

Dependency on ventilation means that a person can no longer breath comfortably without it, and need to use it all of the time.

People start NIV usually for a few hours at night. As their symptoms and breathlessness increase they can choose to use it more often.

Some people choose to use it 24 hours a day. Without it they quickly feel very breathless and uncomfortable. Without it they would become unwell.

Diaphragm muscle

The largest and most important muscle used in breathing. The diaphragm sits below the lungs, around the bottom of the rib cage. It is large and flattish.

You can see an animation of it in the video in How MND/ALS Affects Breathing.

Gas exchange

Gas exchange is how the lungs takes oxygen in from the air to use in the body, and gets rid of the waste gas carbon dioxide. This happens in the lungs. The balance of these gases in the body needs to be kept steady to keep healthy.


A humidifier is an accessory for an NIV machine. It helps to slightly warm and moisten the air. This makes NIV less drying for the mouth and throat.

It typically has a water tank with a metal plate on the base. This warms the water gently and creates a vapour.

This attaches to the NIV machine, and the air passes over the water, taking the vapour with it towards the mask.

Invasive ventilation

Invasive ventilation is when pressurised air is delivered through a tube that is placed directly into the airway.

Most of us have seen on TV the temporary version of this, used for operations or a stay in intensive care.  In this temporary version a small tube is passed from the mouth into the windpipe (trachea) to allow clinicians to manage breathing very carefully.

Some people have invasive ventilation longer term. This is done with a flexible tube that is placed through a smallish hole from the front of the neck (under the Adam’s apple) into the windpipe. This is called a tracheostomy, or trache for short (pronounced ‘trackie’).

'Just in Case' kit

Your GP can order a free MND Just in Case Kit from the MND Association. You keep this box at home, which contains medication prescribed by your GP to use if you feel very breathless.

A doctor or community nurse can use the medication if called out of hours. If appropriate, your GP may also include medication for a carer to give to you while waiting for professional medical help to arrive. Just having the box to hand can feel reassuring.

Lung volume recruitment bag (LVR bag)

A lung volume recruitment (LVR) bag is a piece of equipment that can be used to support the breath stacking technique. A respiratory physiotherapist may give you one and train you how to use it.

See it in use in Keeping Your Chest Clear.

Nippy machine

Some people call their NIV machine their ‘Nippy machine’. ‘Nippy’ is a make of machine for NIV commonly used across the UK.

NIV machine

Any type of machine that can be used for non-invasive ventilation. It is used with a tube or hose, that carries the air flow to a mask worn on the face. It may also be called a BiPAP machine – this is the more clinical name for it.

Non-invasive ventilation

This type of ventilation is delivered using a facial or nasal mask that can be removed. It can be used for short periods of time or up to 24 hour per day.


Oxygen is a gas that is found naturally in the air.  It makes up 20% of the air around us, and all types of animals rely upon it to help release the energy from their food.

As we breathe in air is drawn into the lungs, containing oxygen. The air moves into the smallest parts of the lungs, where oxygen passes across a very thin membrane and into the bloodstream.

It moves to the cells, where they use oxygen to release and use energy from food. After this process the waste gas carbon dioxide is produced, and breathed back our again.

Oxygen therapy

Oxygen therapy should only be used with extreme caution for people with MND/ALS. Some people assume that NIV and invasive ventilation use oxygen. It is in fact normal air under slight pressure.

People with MND/ALS can breathe in enough oxygen. The problem is breathing out enough of the waste gas carbon dioxide.

Being given more oxygen means more carbon dioxide is produced in the body, which can be very dangerous and life threatening at high levels.

Sometime health care staff are unfortunately not aware of this. Ensure any health care team (e.g. in Accident and Emergency) speak to an MND/ALS specialist and carefully monitor your blood gases. You can order an alert wristband from the MND Association to help warn health care staff (details under Alert Wristband).

Respiratory failure

Respiratory failure is a medical term for decreased efficiency in breathing. It may also be called respiratory insufficiency.

In MND/ALS this is the result of weakness in the breathing muscles. This continues to worsen as the condition progresses. This affects levels of oxygen and carbon dioxide in the blood, causing symptoms.

This weakness means the lungs cannot move as much air in and out as the body needs. This can be supported by ventilation.

Respiratory physiotherapist

Respiratory physiotherapists are trained health care professionals. They specialise in looking after people with a range of breathing problems.

The treatments they offer focus on exercises and equipment to support breathing, such a breath stacking and cough assist.

They are also often involved in supporting people using ventilation.


Secretions is a term used to described both mucus and saliva. These can become bothersome in MND/ALS.

Changes to coughing can result in excess mucus or dry mucus. Changes to swallowing can result in excess saliva. use of ventilation can cause a dry mouth.

There are techniques and medications to help manage changes to secretions.


Sedation is a type of medication that relaxes people and reduces their anxiety. There are many types available on prescription. Some are quite mild, others are stronger. Stronger types also tend to reduce people awareness of what is happening around them.

Sedation can be used in MND/ALS to help manage feelings of breathlessness. Stronger types may be used as a person’s condition worsens.

Suction machine

A suction machine is used to help to gently remove secretions (mucus and saliva) from the mouth. It consists of a small pump that creates a low level of suction. This is attached to a tube and a nozzle. It is similar to ones used by dentists.

MND/ALS can cause weakness to the mouth and tongue muscles. This can make it hard to clear the throat and spit.

Tracheostomy or trache

A tracheostomy is a a small opening at the front of the neck into the windpipe (trachea). It is just under the vocal cords. This hole is made by a surgeon.

A small, flexible tube is inserted into this hole to support breathing. This can be attached to a ventilator by a tube. Tracheostomies are often used in intensive care settings as part of ‘life support’.

In the UK they are not commonly used for people with MND/ALS. They can be used if someone really struggles with NIV, or once NIV stops being effective. They need a higher level of care than NIV.


Ventilation is a clinical term, describing the process where air is supported to move in and out of the lungs. This enables a person with weakened breathing to take in enough air and oxygen, and then to breathe out the waste carbon dioxide.

This is done using a machine that gently pumps air through a tube to a person to inflate their lungs, then allows the air to move back out again. There are two types of ventilation – invasive and non-invasive.

Non-invasive refers to using an easy to remove mask. This is as opposed to invasive devices such as tracheostomies or intubation tubes seen typically in intensive care or in operating theatres.

Windpipe (trachea)

The windpipe or trachea is the top part of the airways. It starts below the voice box (larynx) and goes down towards the lungs. When it splits into two (for each lung) it become the bronchi.

Advance care plan

This explanation is about end of life and dying – read when you feel the time is right for you

An advance care plan is a document that outlines the type of care you would prefer to be given at the end of life. It is not legally binding.

However, it offers a useful guide for family and health care teams, especially if you become less able to communicate your wishes.

Advance Decision to Refuse Treatment (ADRT)

This explanation is about end of life and dying – read when you feel the time is right for you

An Advance Decision to Refuse Treatment (ADRT) is a written plan that sets out preferences for care and treatment at the end of life. This plan is discussed with family and the clinical team.

People can choose to put one in place if they want one. It can help them to decide the type of care they want to receive as they become more unwell towards end of life. This can include among other things how breathing support will be managed.

An ADRT is legally binding if the circumstances stated in the form are met. You can revisit and change an ADRT if you wish to, it is not ‘set in stone’.

End of life

This explanation is about end of life and dying – read when you feel the time is right for you

End of life is a term used to describe the time leading up to and around dying. This is the later stages of the condition, as a person becomes weaker and more unwell.

Palliative care

This explanation is about end of life and dying – read when you feel the time is right for you

Palliative care is focused upon managing symptoms and promoting comfort at the end of life. People are usually referred to a specialist palliative care team.

Palliative care teams may be involved for several months, not just the last few days of life. This can help improve symptom control.


This explanation is about end of life and dying – read when you feel the time is right for you

Withdrawal is a term for stopping ventilation once a person has become dependent upon it.

People have the right to refuse a treatment they are being given. They may choose to stop ventilation in the last few hours of their life so they can die without the mask on or the machine running. They may choose to stop it sooner if they feel ventilation has become a burden.

The wish to withdraw can be stated in an Advance Decision to Refuse Treatment (ADRT).

Withdrawal needs careful medical support and strong medication to mange symptoms.