Useful Medical Terminology

Respiratory Terms Glossary:



The term airways is used interchangeably with respiratory system. It refers to the network of organs, muscles and tissues responsible for breathing.


Alveoli are small, balloon-shaped sacs in the lungs where oxygen and carbon dioxide are exchanged.


Apnoea is when the muscles in the throat relax and cause a blockage of the airways.

Sleep apnoea is a common condition that occurs when an individual stops and starts breathing in their sleep. 


Aspiration is when a foreign object or substance (i.e., food or liquid) that is not meant to be swallowed enters the trachea instead of the oesophagus.

It is normal for individuals to aspirate from time-to-time. There are some conditions, however, that predispose people to aspiration. The most notable condition is dysphagia, which is characterised by difficulties swallowing.


The bronchi are tubes that carry air in and out of the lungs via the trachea.


The bronchi split off into smaller airways known as the bronchioles. The bronchioles lead to the alveoli where the exchange of oxygen and carbon dioxide occurs.


Bronchitis is an infection that occurs in the bronchi. Symptoms of bronchitis include breathlessness, coughing, and a high temperature.


A bronchospasm is when the muscles in the bronchi tighten and narrow. This can lead to difficulty breathing, wheezing and chest pain.

Chronic Obstructive Airways Disease (COPD)

Chronic Obstructive Airways Disease (COPD) is a term used to define a cluster of conditions that cause severe breathing difficulties. COPD is characterised by restricted airflow, coughing and a persistent shortness of breath.

The most common causes of COPD are tobacco use and air pollution. According to the World Health Organisation (WHO), COPD is the third leading cause of death in the world. 

There is currently no cure for COPD. However, with proper treatment, some of the symptoms of the disease can improve.


Cilia are small, hair-like projections in the lungs. They move backwards and forwards together in a fan-like manner to push mucous and foreign particles up into the mouth, where they can be expelled.


Cyanosis refers to the blue and purple hue that the skin takes on when there is a reduced oxygen supply in the blood. Cyanosis can indicate that there is an issue with the lungs. 


Decannulation is the removal of a tracheostomy. A tracheostomy is usually removed when a patient’s condition improves and enables them to breathe on their own without medical intervention.


The diaphragm is the main muscle that supports the process of breathing. When you breathe in, the diaphragm contracts and creates a vacuum that draws air into the lungs. When you breathe out, the diaphragm relaxes and forces air out of the lungs.


Emphysema is a type of COPD. Emphysema is when the alveoli in your lungs are damaged. The main symptoms of emphysema are shortness of breath and a persistent cough.

Emphysema is caused by tobacco use and air pollution.


An endoscopy is a test that looks inside the body with a camera. During an endoscopy, a tube is inserted into the body via a natural opening (i.e., the mouth).

Gas exchange

Gas exchange is the process by which oxygen is moved from the lungs to the bloodstream and carbon dioxide is moved from the blood to the lungs where it can be exhaled.

Graduated suction catheter

When a suction catheter is graduated, it means that the length of the tube is marked in centimetres. The graduations typically begin 4cm from the distal end of the catheter.


Hyperventilation is the term for rapid breathing that creates an imbalance between the oxygen being inhaled and the oxygen being exhaled.


Hypoxia is when there is insufficient oxygen in the tissues. This makes it difficult to maintain homeostasis. 

Intracranial pressure

Intracranial pressure is an increase of pressure in the brain. This pressure can appear suddenly or build up gradually.

Intracranial pressure can happen because of a head injury or spinal fluid leaking into the brain. Suctioning using a catheter can also lead to an increase in intracranial pressure.


Intubation is a medical procedure performed on patients having difficulty breathing. Intubation consists of inserting a tube into the nose or mouth and pushing it down into the trachea. The tube is typically attached to a mechanical ventilator.


A laryngectomy is a procedure to remove part or all of the larynx. The procedure is normally carried out to remove cancer.


The larynx is often referred to as the voice box. It sits above the trachea (windpipe) and in front of the oesophagus.

The larynx is responsible for producing sound and protects the lower respiratory tract from food.



Lungs are the primary organs in the respiratory system. They form part of a wider network of muscles and tissues that enable breathing.

Lower airway

The lower airway, sometimes known as the lower respiratory tract or lower respiratory system, consists of the trachea, bronchi and bronchioles.

Mechanical ventilator

Mechanical ventilators are machines designed to support breathing. They work by moving air in and out of lungs using an endobronchial tube.

Nasal cannula

A nasal cannula is a tubular and two pronged device that is inserted into the nostrils to supplement oxygen supply.


The nasopharynx is the top part of the throat. It enables the air that comes in through the nose to pass through to the trachea. 


A nebuliser is a device that transforms liquid medicine into a fine mist that can be breathed in easily. A nebuliser will typically be used when the effects of a standard inhaler no longer suffice in treating the symptoms of certain respiratory conditions.


The oesophagus is a muscular tube that connects the throat to the stomach. It is sometimes known as the food pipe. 


Oxygenation is a procedure that supports the respiratory system. It is when oxygen is administered to an individual via a mask or tube.

Oxygen saturation

Oxygen saturation is another term for blood oxygen level. More specifically, it refers to the measurement of haemoglobin in the blood.

The oxygen saturation is determined via the use of a pulse oximeter.


The pharynx is more commonly called the throat. The pharynx is both a respiratory and digestive tract. It connects the mouth and the nose to the larynx and oesophagus.


Phlegm is a mucus secreted by cells in the lower airways (the trachea and bronchi). Phlegm traps foreign particles that enter the lungs. These particles are then removed when the phlegm is coughed up through the airways.

Phlegm is usually clear or somewhat cloudy in colour. However, if an individual is unwell or has an infection, the colour may range from dark yellow to green.

The word phlegm is sometimes used interchangeably with sputum.


Pneumonia is inflammation of the lungs caused by an infection. When an individual has pneumonia, the tiny air sacs in their lungs (alveoli) fill up with pus or fluid. This can lead to difficulty breathing, as well as coughing and wheezing.

Pneumonia can affect one or both lungs. It is normally treated with antibiotics and clears up within 4 weeks. However, some cases of pneumonia are more serious and may require more serious medical attention (i.e., hospitalisation).

Respiratory system

The term respiratory system refers to the muscles, organs and tissues that are involved in breathing.


Saliva is a substance secreted by the salivary glands. It is made up of water, electrolytes and enzymes.

Saliva lubricates the mouth and throat. It also helps with swallowing and digestion.


Secretions are the substances produced by the organs and glands in the body.


A spirometry is a test used to diagnose and monitor lung-related conditions.

Suction catheter

A suction catheter is a device used to remove secretions (i.e., sputum and saliva) from the respiratory tract to prevent an obstruction in the airways. The suction catheter is a tube that can be inserted directly into the throat or via a tracheostomy to keep the airways open.


Sputum is a mucus secreted by the cells in the lower airways (the trachea and the bronchi). 

Sputum is another word for phlegm.


Suctioning is a medical procedure that removes secretions from the respiratory tract to prevent a blockage that makes it more difficult to breathe. Suctioning is sometimes performed through an artificial airway such as a tracheostomy.

Upper airways

The upper airways, also known as the upper respiratory tract, consist of the nasal cavity, oral cavity, pharynx and larynx.


The trachea, often referred to as a windpipe, is the main airway into the lungs. It splits off into the bronchi.


A tracheostomy is an artificial opening created at the front of the neck to support breathing. A tube is inserted into the hole, which makes it easier for an individual to breathe. In some cases, the tube may be attached to a ventilator.


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Please note that while every effort is made to ensure the accuracy of the content presented, it is purely for educational purposes only and is not a substitute for professional medical advice.