The words below are common medical terms you may find useful in your efforts to understand more about COPD.

Acute symptoms—Symptoms that come on abruptly or over a short period of time. The opposite of chronic.

Alveoli—Tiny saclike air spaces in the lungs, where there's a transfer of carbon dioxide from the blood into the lungs, and of oxygen from the lungs into the blood.

Artery—A blood vessel that carries blood from the heart to the organs and other parts of the body; arteries usually carry blood rich in oxygen.

Arterial blood gas (ABG)—Blood is withdrawn from a small artery and then analyzed by a special machine that records the amount of carbon dioxide (waste gas) and oxygen in the blood. This test can help determine whether or not one needs extra oxygen.

BID—A term that refers to taking one's medicine twice a day.

Biopsy—Surgical removal of a small amount of tissue for examination and diagnosis. Biopsies can be used to differentiate between cancerous and noncancerous tissue.

Bronchi—These are the large hollow air passages of the lungs.

Bronchial tubes—Hollow air passages that branch out from the trachea, or windpipe, into the lungs. Oxygenated air passes into the lungs through these tubes, while waste gases like carbon dioxide pass out.

Bronchioles—Air passages that are so small they can be seen only through a microscope. They serve the same purpose as the bronchi.

Bronchoscope—A tubular instrument, with lenses and lights, that is inserted through the upper airway into the bronchial tubes.

Bronchoscopy—A procedure in which a bronchoscope is inserted into the upper airway through the trachea and branching segments of the bronchi. Fluid or tissue may be removed and examined to detect tumors, infection, or determine the cause of inflammatory lung conditions.

Bronchodilation—The increase in diameter of the bronchi and bronchioles because the airway muscles are relaxed.

Carbon dioxide (CO₂)—A colorless, odorless, nonflammable gas produced when one breathes. CO₂ is eliminated by the tissues into the blood, to be exhaled by the lungs in exchange for oxygen (O₂).

Chronic symptoms—Those symptoms that occur over weeks, months, or years. The opposite of acute.

Chronic bronchitis—Inflammation of the airways that causes increased mucus to be produced. Bronchitis is considered chronic (or long-term) if one coughs and produces excess mucus most days during three months in a year, for two years in a row.

Cilia—Tiny, hairlike structures that line the airways. In healthy lungs, cilia propel bacteria, pollutants, and other irritants upwards so they can be expelled. Cigarette smoking prevents cilia from working properly. And in patients with COPD, the cilia may be injured and unable to perform optimally, if at all.

Compliance—In medical language, the practice of taking one's medicines and following medical directions correctly and in full.

Diaphragm—The curved muscle that separates the chest from the abdomen. When we inhale, it flattens, then sinks, to help draw air into the lungs.

Dilate—To widen a circular opening, like the inside of a tube, the airways in the lungs, or the pupil of the eye.

Dyspnea—Difficult or labored breathing; shortness of breath.

Emphysema—A disease that affects the air sacs and/or the smallest breathing tubes in the lungs. As the lungs lose elasticity, similar to an overused rubber band, the affected areas become enlarged.

Exacerbation—An increase in the severity of a disease or any of its signs and symptoms.

Glucose—Also known as sugar, glucose is the chief source of energy for living organisms.

Hepatic—Referring to the liver.

Hypersensitivity—A reaction to a particular food, drug, or chemical. It may occur on the skin or throughout the body and may become life-threatening.

Mucus—A thick liquid that moistens and lubricates body tissues, including those in the airways and lungs.

Nebulizer—A device that sprays liquid medicine in aerosol form, into the air one breathes.

Oxygen (O₂)—Colorless, odorless gas essential for all life processes. It's the most important component of air.

Phlegm—Thick, sticky, stringy mucus produced by the respiratory tract, usually as the result of irritation, inflammation, or infection of the airways.

Pharyngitis—Inflammation of the pharynx that causes a sore throat.

Productive cough—A cough in which mucus or phlegm is released, enabling a person to clear his or her lungs.

Pulmonary—Referring to the lungs.

Pulse oximetry—A test performed by placing a special light clip on your finger, earlobe, or forehead. The pulse oximeter uses light waves to indirectly measure the amount of oxygen in your blood. Pulse oximeters can measure oxygen levels continuously and can be performed while the patient is resting, walking, or even sleeping.

Respiratory tract—The entire system of air passages involved in breathing, especially the trachea, bronchial tubes, bronchioles, and alveoli.

Rhinitis—Inflammation of the lining of the nose.

Spirometer—A machine for measuring how well the lungs allow a person to breathe.

Sputum—Mucus, phlegm, or other substances coughed up from the respiratory tract.

Trachea—The windpipe. The trachea is the main air passageway from the mouth and nose to the lungs. The trachea ends when it divides into the right and left main bronchi.

Ventilation—The movement of air into and out of the lungs to remove carbon dioxide.

Wheezing—The sound made by air moving through partially obstructed airways.

Chest X-ray—A chest x-ray helps medical professionals see parts of the lungs and diagnose pneumonia and emphysema, as well as other lung diseases.