Asthma Glossary of Terms

Medically Reviewed by Dan Brennan, MD on July 20, 2021
8 min read

Allergen: a substance (such as a food or pollen) that your body perceives as dangerous and can cause an allergic reaction.

Allergy: an exaggerated response to a substance or condition produced by the release of histamine or histamine-like substances by affected cells.

Alveoli: thin-walled, small sacs located at the ends of the smallest airways in the lungs where the exchange of oxygen and carbon dioxide takes place.

Antibiotic: medication used to treat infection caused by bacteria. Antibiotics do not protect against viruses and do not prevent the common cold.

Anticholinergics: (also called cholinergic blockers or "maintenance" bronchodilators). This type of medicine relaxes the muscle bands that tighten around the airways. This action opens the airways, letting more air out of the lungs to improve breathing. Anticholinergics also help clear mucus from the lungs.

Antihistamine: medication that stops the action of histamine, which causes symptoms of allergy such as itching and swelling.

Anti-inflammatory: medication that reduces inflammation (swelling in the airway and mucus production).

Asthma: a disease of the airways or branches of the lung (bronchial tubes) that carry air in and out of the lungs. Asthma causes the airways to narrow, the lining of the airways to swell and the cells that line the airways to produce more mucus. These changes make breathing difficult and cause a feeling of not getting enough air into the lungs. Common symptoms include cough, shortness of breath, wheezing, chest tightness, and excess mucus production.

Bacteria: infectious organisms that may cause sinusitis, bronchitis, or pneumonia.

Beta2-agonists: a bronchodilator medication that opens the airways of the lung by relaxing the muscles around the airways that have tightened (bronchospasm). These medications may be short acting (quick relief) or long acting (control) medications. Short acting beta2 agonists are the drugs used to relieve asthma symptoms when they occur.

Breath sounds: lung sounds heard through a stethoscope.

Breathing rate: the number of breaths per minute.

Bronchial tubes: airways in the lung that branch from the trachea (windpipe).

Bronchioles: the smallest branches of the airways in the lungs. They connect to the alveoli (air sacs).

Bronchodilator: a drug that relaxes the muscle bands that tighten around the airways in asthma. Bronchodilators can also help clear mucus from the lungs.

Bronchospasm: the tightening of the muscle bands that surround the airways, causing the airways to narrow.

Carbon dioxide: a colorless, odorless gas that is formed in the tissues and is delivered to the lungs to be exhaled.

Chronic disease: a disease that can be controlled, but not cured.

Cilia:hair-like structures that line the airways in the lungs and help to clean out the airways.

Clinical trials: research programs conducted with patients to evaluate a new medical treatment, drug, or device. The purpose of clinical trials is to find new and improved methods of treating different diseases and special conditions.

Contraindication: a reason not to use a course of treatment or medication.

Dander, animal: tiny scales shed from animal skin or hair. Dander floats in the air, settles on surfaces and is a major part of household dust. Cat dander is a classic cause of allergic reactions.

Decongestant: medication that shrinks swollen nasal tissues to relieve symptoms of nasal swelling, congestion, and mucus secretion.

Dehydration: excessive loss of water.

Diaphragm: the major muscle of breathing, located at the base of the lungs.

Dry powder inhaler (DPI): a device for inhaling respiratory medications that come in powder form.

Dust mites: a common trigger for allergies.

Dyspnea: shortness of breath.

Exacerbation: worsening.

Exercise induced asthma: asthma that is made worse when exercising

Exhalation: breathing air out of the lungs

(HEPA) high-efficiency particulate air filter: a filter that removes particles in the air by forcing it through screens containing microscopic pores.

Histamine: a naturally occurring substance that is released by the immune system after being exposed to an allergen. When you inhale an allergen, mast cells located in the nose and lungs release histamine. Histamine then attaches to receptors on nearby blood vessels, causing them to enlarge (dilate). Histamine also binds to other receptors located in nasal tissues, causing redness, swelling, itching, and changes in the secretions.

Holding chamber: see spacer.

Humidification: the act of moisturizing the air with molecules of water.

Hydrofluoroalkane Inhaler (HFA): small aerosol canister in a plastic container that releases a mist of medication when pressed down from the top. This drug can be breathed into the airways. Many asthma medications are taken using an HFA, which was formerly called a "metered dose inhaler."

Hyperventilation: excessive rate and depth of breathing.

Immune system: the body's defense system that protects us against infections and foreign substances.

Indication: reason to use.

Inflammation: a response in the body that may include swelling and redness.

Inhaler: See Hydrofluoroalkane Inhaler (HFA)

Inhalation: breathing air into the lungs.

Irritants: things that bother the nose, throat, or airways when they are inhaled (not an allergen).

Leukotriene modifier: drug that blocks chemicals called leukotrienes in the airways. Leukotrienes occur naturally in the body and cause tightening of airway muscles and production of excess mucus and fluid. Leukotriene modifiers work by blocking leukotrienes and decreasing these reactions. These medications may also be helpful in improving airflow and reducing some symptoms of chronic obstructive pulmonary disease (COPD).

Medical history: a list of a person's previous illnesses, present conditions, symptoms, medications, and health risk factors.

Metered dose inhaler (MDI): See Hydrofluoroalkane Inhaler (HFA)

Mold: parasitic, microscopic fungi (like those in the genus Penicillium that produce penicillin) with spores that float in the air like pollen. Mold is a common trigger for allergies and can be found in damp areas, such as the basement or bathroom, as well as in the outdoor environment in grass, leaf piles, hay, mulch, or under mushrooms.

Monitoring: keeping track of.

Mucus: a material produced by glands in the airways, nose, and sinuses. Mucus cleans and protects certain parts of the body such as the lungs.

Nasal spray: medication used to help prevent and treat nasal congestion or nasal allergy symptoms. Available by prescription or over-the-counter in decongestant, corticosteroid, or salt-water solution form.

Nebulizer: a machine that changes liquid medicine into fine droplets (in aerosol or mist form) that are inhaled through a mouthpiece or mask. Nebulizers can be used to deliver bronchodilator (airway-opening) drugs such as albuterol and Atrovent, as well as anti-inflammatory or steroid medicines (Pulmicort Respules). A nebulizer may be used instead of a metered dose inhaler (MDI). It is powered by a compressed air machine and plugs into an electrical outlet.

Non-steroidal: anti-inflammatory medication that is not a steroid. Also see steroid.

Oxygen: the essential element in the respiration process to sustain life. This colorless, odorless gas makes up about 21% of the air.

Peak Expiratory flow rate: a test used to measure how fast air can be exhaled from the lungs.

Peak flow meter: a small hand-held device that measures how fast air comes out of the lungs when a person exhales forcefully. This measurement is called a peak expiratory flow (PEF) and is measured in liters per minute (lpm). A person's PEF may drop hours or even days before asthma symptoms are noticeable. Readings from the meter can help the patient recognize early changes that may be signs of worsening asthma. A peak flow meter can also help the patient learn what trigger their symptoms and understand what symptoms indicate that emergency care is needed. Peak flow readings also help the doctor decide when to stop or add medications.

Personal best peak expiratory flow (PEF): the highest peak flow number a person can achieve when symptoms are under good control. The personal best PEF is the number to which all other peak flow readings will be compared. In children, peak expiratory flow rates are based on how tall the child is. Therefore, the personal best peak expiratory flow will change as growth occurs. A child's personal best peak expiratory flow should be redetermined approximately every 6 months or when a growth spurt has occurred.

Pneumonia: an infection of the lung that can be caused by bacteria, a virus, or a fungus..

Pollen: a fine, powdery substance released by plants and trees; an allergen.

Pollen and mold counts: a measure of the amount of allergens in the air. The counts are usually reported for mold spores and three types of pollen: grasses, trees, and weeds. The count is reported as grains per cubic meter of air and is translated into a corresponding level: absent, low, medium, or high.

Productive cough: a "wet" cough that may involve coughing up mucus.

Puffer: another term for inhaler or metered dose inhaler.

Pulmonary function tests(PFTS): a test or series of tests that measure many aspects of lung function and capacity; also referred to as lung function tests.

Pulse oximetry: a test in which a device that clips on the finger measures the oxygen level in the blood.

Respiration: the process of breathing which includes the exchange of gases in the blood (oxygen and carbon dioxide), the taking in and processing of oxygen, and the delivery of carbon dioxide to the lungs for removal. See inhalation and exhalation.

Sinuses: air pockets inside the bones of the head and face that link to the nose.

Spacer: a chamber that is used with a metered dose inhaler to help the medication get into the airways better. Spacers also make metered dose inhalers easier to use; spacers are sometimes called "holding chambers."

Spirometry: a basic pulmonary function test that measures how much and how fast air moves out of the lungs.

Sputum: mucus or phlegm.

Steroid: medication that reduces swelling and inflammation. Comes in pill, injected, and inhaled forms. Also called corticosteroid.

Symptom: what someone will experience as a result of a disease or illness, like pain, cough, or shortness of breath, for example.

Theophylline: a long- term control medication that opens the airways, which helps prevent and relieve bronchospasm.

Trachea: the main airway (windpipe) supplying both lungs.

Triggers: things that cause asthma symptoms to begin or make them worse.

Vaccine: a shot that protects the body from a specific disease by stimulating the body's own immune system.

Wheezing: the high-pitched whistling sound of air moving through narrowed airways.