Term Glossary
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Accessory Muscles of Respiration: Muscles that are generally not used in regular breathing, but that can be recruited to assist in breathing during an acute attack of dyspnea (shortness of breath).

Acinus: A cluster of alveoli at the end of a tiny respiratory airway in the lung.

Acute: An adjective that is generally used to refer to an event of sudden or severe onset and short duration.

Airway Epithelium: The layer of cells that line the airways. These are called epithelial cells and consist of five major types and a number of minor cell types. The major cell types are ciliated, basal, goblet, serous and undifferentiated.

Airways: Tubular structures within the neck (trachea) and lungs (bronchi, bronchioles, bronchioli) that allow passage of air into and out of the lungs.

Albinism: A defect of melanin production that results in little or no color (pigment) in the skin, hair, and eyes.

Alpha-1 antitrypsin (AAT): A medium sized protein that blocks the destructive action of a group of proteins called proteases. AAT is the primary blocker of neutrophil elastase, a powerfully destructive protease released from neutrophils during lung inflammation that destroys lung tissue and causes emphysema.

Alpha-1 antitrypsin deficiency (AAT deficiency): A inherited disease characterized by reduced levels or the absence of AAT in the blood and tissues that results in lung and liver disease.

Alveolar Macrophages: Mobile cells that normally reside within alveoli and perform a number of critical functions in health and disease. Alveolar macrophages serve a critical function in surfactant homeostasis by removing excess surfactant lipids and surfactant proteins from the alveoli. They also protect the lung by internalizing and destroying inhaled microbial organisms (e.g., bacteria), and by removing inhaled particulates. Alveolar macrophages also participate in inflammation, repair of damaged lung tissues, eliminating cancer cells and a number of other functions.

Alveoli: Tiny sac-like air spaces in the lungs where transfer of carbon dioxide from blood into the lungs and oxygen from air into blood takes place.

Angiomyolipoma: Benign tumors of the kidney and are composed of blood vessels, smooth muscle cells, and fat cells.

Antibiotic: A class of drugs that either inhibit the growth of or kill microbial pathogens like bacterial, fungal or viral organisms.

Antibodies: Protective proteins produced by the immune system that recognize and bind to foreign molecules (antigens).

Anti-cholinergic: A class of drugs blocks (opposes the action of) acetylcholine, a protein that transmits nerve impulses between nerve cells. In emphysema, anti-cholinergic drugs are used to block nerve impulses to the muscles in the walls of the respiratory airways.

Arterial Blood Gas (ABG): A test in which blood is taken from an artery and used to determine the amounts of oxygen and carbon dioxide in the blood.

Arteriole: The smallest artery; it connects larger arteries to the capillary network.

Artery: A blood vessel that carries blood away from the heart and towards a part of the body.

Asthma: A lung disease characterized by narrowing of the respiratory airways. Symptoms include recurrent attacks of wheezing, coughing, shortness of breath (dyspnea).

b.i.d.: An abbreviation for the Latin term "bis in di'e", meaning twice a day

Beta 2 Agonist: A type of drug that relaxes the muscles within the respiratory airway thus allowing the airways to expand resulting in relief of dyspnea.

Blebs: Cysts on or near the surface of the lungs.

Bronchial tubes, Bronchi: Respiratory airways within the lung that usually larger and closer to the throat.

Bronchiole: Respiratory airways within the lungs that is smaller and farther away from the throat. These are the smallest air tubes within the lung and branch off of larger bronchi and join to alveolar ducts, and to alveolar acini.

Bronchiolitis: Inflammation of the bronchioles. Bronchiolitis is frequently caused by viral infection of the lungs.

Bronchodilator: A type of drug that relaxes the muscles within the respiratory airway thus allowing the airways to expand resulting in relief of dyspnea. See Beta 2 agonist and steroids.

Bronchopulmonary: Pertaining to the lungs and air passages.

Bronchoscopy: A procedure in which a small, flexible tube is passed through a nostril or the mouth and into the larger airways of the lungs. The bronchoscope tube has several channels including a fiberoptic light path and a suction channel, which permit direct visualization of the airway surfaces and collection of lung fluid or tissues, respectively.

Capillaries: The smallest blood vessels in the body. A network of capillaries in tissues connects arterioles that bring blood to the tissues with venules that return blood to the heart.

Cell: The smallest unit of a living structure capable of independent existence, composed of a membrane-enclosed mass of protoplasm and containing a nucleus or nucleoid.

Chest: The anterior wall of the thorax, the upper part of the body between the neck and the abdomen.

Chest Cavity: Space in body surrounding the lungs.

Chyle: A milky fluid consisting of lymph and droplets of triglyceride fat that becomes mixed with the blood.

Chronic: Referring to a health-related state, lasting a long time.

Chronic Bronchitis: A respiratory disease characterized chronic coughing that lasts for more than three months per year on successive years. It may be accompanied by changes in structure of the airways of the lungs, inflammation, and enlargement of the mucous glands.

Chronic Obstructive Pulmonary Disease: A general term used for lung diseases with permanent or temporary narrowing of small bronchi, in which forced expiratory flow is slowed. It is frequently used when no etiologic or other more specific term can be applied.

Cilia: Motile extensions of the surface of some airway epithelial cells that look like short thick hairs and act as filters in the nose and upper airway, using a wave-like motion.

Colitis: Inflammation of the colon that can be associated with diarrhea, abdominal pain, bloating, and blood in the stool

Collagen: A group of rigid, fibrous proteins that serve as the main components of connective tissues of the body. Collagen is usually found in the interstitium between cells.

Computed Tomography (CT) Scan: A test in which x-rays are used to create a picture of the body (i.e., a chest CT scan of the lungs), using a computer-controlled machine (CT scanner).

Congenital: Existing at birth.

Cor Pulmonale (right-sided heart failure): A disease of the heart characterized by enlargement of the right ventricle. It is caused by increased resistance to blood flow through the lung and can occur in severe lung disease and lead to heart failure.

Corticosteroid: A class of steroid-type drugs that are used to suppress inflammation and function as slow-acting bronchodilators. Examples include prednisone, cortisone, fluticasone, beclomethasone, and others. Steroids are similar to hormones produced in the body's adrenal glands that serve as chemical messengers.

Crackle: An ambiguous term used by doctors to describe an abnormal sound heard when listening for breath sounds during examination of the chest. It is used by some to denote rhonchus and by others to denote crepitation. It is a synonym for the term "rale".

Crepitation: A specific term used by doctors to describe an abnormal sound heard when listening for breath sounds during examination of the chest. It denotes a fine bubbling sound that resembles the noise heard on rubbing hair between the fingers.

Cyanosis: A bluish color of skin, fingernails, and mucous membranes that indicates low level of oxygen in the blood.

Cystic Fibrosis: A inherited disease caused by mutations of the CFTR gene that affects the excretory glands, lungs, pancreas and other organs. In the lungs, cystic fibrosis associated with the presence of thick mucus, bacterial colonization of the airways and repeated bouts of acute exacerbations of the lung disease.

Diaphragm: The muscle on which the lungs and heart rest that separates the chest and abdominal cavity and serves as the primary muscle used for breathing.

Diffusion Capacity: A pulmonary function test that measures the ability of the lung to permit the passage of gas into the blood.

Diuretic: A type of drug that promotes the excretion of salt and water by the kidney and thus increases urine output.

Duct: Tubular structures within the body with well-defined walls that usually permits passage of air or liquids.

Dysplasia: Abnormal growth or development of tissue.

Dyspnea: Difficulty breathing, frequently referred to as "shortness of breath," "chest tightness" or "hard, labored breathing".

Edema: An abnormal swelling resulting from the excessive accumulation of watery fluid in interstitial spaces between cells in tissues of the body.

Elastin: A type of protein that serves as the main component of elastic fibers in the body.

Emphysema: A chronic lung disease characterized by destruction of portions of the tissues distal to the terminal bronchioles, i.e., those parts containing alveoli that result in reduced numbers of alveoli and enlarged alveolar spaces. An important clinical manifestation is breathlessness on exertion, due to the reduction of alveoli available for gas exchange and collapse of small airways and trapping of alveolar gas on expiration. Air trapping prolongs expiration, increases the residual volume and causes the chest to become enlarged ("barrel chest").

Endotracheal Tube: An open-ended plastic tube that is placed within the trachea usually to allow assisted breathing by mechanical ventilation.

Expiration: The act of expelling air from the lung, i.e., breathing out.

Expiratory Reserve Volume (ERV): A pulmonary function test that measures the maximum volume of air expired from the lung starting from the position at the end of a breath during quiet breathing.

Fetus: The unborn offspring of an animal following the embryonic period, i.e., from 8 weeks after conception until birth.

Forced Expiratory Flow 25-75%: A pulmonary function test that measures the forced expiratory flow during the middle half of the FVC. This test was previously referred to as the maximum midexpiratory flow rate.

Forced Expiratory Volume in one second (FEV 1): A pulmonary function test that measures the volume of air expired during the first second of a forced exhalation from the position of maximal inspiration.

Forced Vital Capacity (FVC): A pulmonary function test that measures the maximum volume of air forcibly expired from the maximum inspiratory position.

Gas Exchange: The process in which oxygen from inhaled air is transferred into the blood and carbon dioxide from the blood is transferred into the alveoli. It is a primary function of the lung and occurs across the alveolar wall.

Genetic Disease: A disease that passed on to an individual by genes (DNA) obtained from one or both parents.

Hemoptysis: Coughing up blood or blood-stained sputum.

Hyaline Membrane Disease: A respiratory disease of newborns in which dead lung cells and proteins form a "membrane" within the alveoli making gas exchange difficult or impossible. It occurs more frequently in infants that are born prematurely before the lungs are able to make adequate amounts of surfactant.

Hypertension: High blood pressure.

Hypoxemia: Low levels of oxygen in the blood.

Immunization: A biological drug that stimulates the immune system to develop protective responses, usually antibodies, against a specific infectious organism or group of organisms. Vaccines are frequently made from killed or attenuated microbial organisms. Newer vaccines are sometimes made from proteins or DNA purified from microbial organisms.

Inflammation: A natural response of the body to injury characterized by recruitment of specialized white blood cells into the tissues, edema and increased metabolic activity. Inflammation can occur in any part of the body including the airways; in the skin, inflammation is accompanied by swelling, redness, and pain. These signs also occur during inflammation of the airways and can be seen during bronchoscopy.

Inflammatory bowel disease: Chronic inflammation of all or part of the digestive tract.

Inspiration: The act of bringing air into the lungs, i.e. taking in a breath.

Interstitial: The space between the cells of a tissue or organ, but excluding empty spaces such as body cavities and potential spaces (e.g., pleural space).



Lung Biopsy: A procedure in which a specimen of lung tissue is taken for examination. Various approaches can be used to obtain lung biopsies including bronchoscopy, a transthoracic needle, or surgery.

Lung Reduction Surgery: A surgical procedure in which dead or damaged lung tissue is cut away, leaving room for healthy lung tissue to expand.

Lung: One of a pair of viscera (internal organs) occupying the chest cavity of the thorax that serve as the organs of respiration in which gas exchange occurs.

Lymph: A transparent, slightly yellow liquid found in the lymphatic vessels. Lymph is collected from tissue fluids throughout the body and returned to the blood via the lymphatic system.

Lymphangioma: Malformations of the lymphatic system, which is a network of vessels responsible for returning to the venous system excess fluid from tissues.

Mechanical Ventilation: A life-preserving procedure in which a machine called a mechanical ventilator is used to delivery air to the lungs via an endotracheal tube. Mechanical ventilation is used in cases where gas exchange is impaired or lung failure has occurred.

Membrane: This term has several meanings depending on the usage. In reference to a cell, the outer or limiting membrane is the thin, flexible film that encloses the contents of a cell and is comprised of a double layer of lipids containing various attached and embedded proteins; it controls what substances go into and come out of the cell. In reference to a tissue, the membrane is a thin layer of cells that covers the surface of the tissue or lines the cavity of an organ.

Metered-Dose Inhaler (MDI): A medication container that, when activated by pushing a trigger, delivers a pre-measured dose of medication that is inhaled directly into the lungs.

Mucociliary Escalator: A mechanism by which mucous is propelled towards the nose and eliminated by coughing or sneezing. Cilia on the surface of the specialized airway epithelial cells form a thick carpet of fibers that beat in unison and create wave like movement of a fluid layer that covers the inside surface of the airway tube. Consequently, the mucous that sits atop this "pericellular" fluid layer is propelled towards the nose like "mucous surfboards", carrying their cargo of inhaled microbes and particulates out of the lungs.

Mucous: A sticky substance produced by specialized (goblet) cells within the respiratory tract. After synthesis it is stored in mucous droplets in goblet cells until it is needed, at which time it is expelled from the cell and sits atop the pericellular fluid layer that coats the airway epithelium. The sticky material "catches" inhaled particulates and is then eliminated from the body by the mucociliary escalator. Mucous is the major component of phlegm that is expectorated from the lungs in individuals with a "productive" cough. Lung diseases associated with airway inflammation (acute and chronic bronchitis, asthma, COPD) often lead to increased production of mucous.

Nasal Flaring: An outward motion of the nostrils during breathing; it can be an indication of dyspnea or labored breathing.

Neonatal Period: The initial period of life of the newborn; usually referring to the first 4 weeks after birth.

Neonatologist: A doctor specializing in the care and treatment of diseases of newborn babies.

Neutrophils: A mobile cell made in large numbers in the bone marrow and released into the blood. They can be recruited into the lungs and other tissues by specific substances released at sites of inflammation to help to protect against infections. Neutrophils are capable of releasing large amounts of destructive enzymes that can damage the interstitium and cells of the tissue, especially when levels of alpha-1 antitrypsin are very low. In the lungs, this process can lead to emphysema. Smoking results in increased recruitment of neutrophils and other molecular events that damage the tissue and result in emphysema. However, neutrophils represent a "double-edged sword" because they are vital to the normal host defense mechanisms.

Oculocutaneous albinism: A form of albinism involving the eyes, skin, and according to some definitions the hair as well. Four types of oculocutaneous albinism have been described, all caused by a disruption of melanin synthesis and all autosomal recessive disorders.

Oxygen: A colorless, odorless gas that constitutes 21% of the air we breathe at sea level. Oxygen combines naturally with many other elements to form oxides (i.e., rust on iron). It is essential to life because is provides the energy used to "power" a wide variety of chemical reactions that occur in the cells of the body.

Pathogenesis: The molecular and cellular events that lead to or cause a disease.

Pathophysiology: A term used to describe the abnormal physiological functioning of an organ, cell or molecular process.

Peak Expiratory Flow (PEF): A pulmonary function test that measures the maximum value for the expiratory flow of air from the lungs during a forced exhalation.

Physiology: A term used to describe the mechanistic functioning of an organ, cell or molecular process.

Platelets: Blood cells whose function (along with the coagulation factors) is to stop bleeding.

Pleura: The serous membrane (sheet of cells) covering the surface of the lungs and lining the inside walls of the chest cavity. The visceral pleura cover the surface of the lung (one of the visceral organs, or viscera) and the parietal pleura covers the inside of the chest wall.

Pleural Cavity: The space between the parietal and visceral layers of the pleura. The pleural cavity (also called pleural space) is a potential space, meaning that it is normally not occupied with anything more than a tiny amount fluid that serves as a lubricant for the visceral and parietal pleural surfaces. The pressure within the pleural cavity is normally negative (i.e., a vacuum) with respect to the atmosphere and this helps keep the lung inflated to the fullest extent possible. However, if the lung surface or chest wall is damaged, air can enter the pleural cavity resulting in collapse of the lung (see pneumothorax). Fluid can also accumulate in these spaces (see pleural effusion) and compress the lungs, thus impairing breathing.

Pleural Effusion (Pleural Fluid): An abnormal accumulation of fluid within the pleural cavity. It can be consist of watery fluid that accompanies serious heart failure, inflammatory cells and proteins that accompanies lung infection, and chylous lymphatic fluid that can occur in lymphangioleiomyomatosis (LAM).

Pneumococcal Vaccine: A drug made from a killed preparation of a common pneumonia causing bacteria (Streptococcus pneumoniae) that stimulates a person's immune system to develop specific antibodies that can recognize and prevent subsequent infections by this group of bacteria.

Pneumonia: Inflammation of the lung tissues characterized by filling of the alveolar air spaces with exudate, inflammatory cells and blood protein (fibrin). Most cases are due to infection by bacteria or viruses, but some are caused by inhalation of chemicals or trauma to the chest wall or by infection by other less common microorganisms.

Pneumothorax: A partial or complete collapse of the lung resulting from the abnormal entry of gas into the pleural cavity.

Positive Pressure Ventilation: A type of assisted breathing where air, frequently mixed with increased amounts of oxygen, is delivered under pressure by a mechanical respirator.

Prenatal: A term referring to the period of life of a fetus that occurs before birth.

Progressive: A term used to describe the course or natural history of a disease. It is frequently used, when unqualified, to indicate an unfavorable course.

Pulmonary: Relating to the lungs or the pulmonary artery.

Pulmonary Edema: An abnormal accumulation of fluid in the lungs. It can occur in association with severe heart failure when watery fluid "leaks" out of the pulmonary capillaries into the interstitium of the lung and, eventually, into the alveoli and terminal airways.

Pulmonary Fibrosis: A disease marked by scarring in the lungs. Tissue deep in the lungs becomes thick, stiff and scarred. It interferes with a person’s ability to breathe.

Pulmonary Hypertension: Abnormally high blood pressure in the arteries of the lungs.

Pus: A thick, opaque, and usually yellowish/greenish fluid that contains white blood cells, bits of destroyed tissue, and microorganisms.

q.d.: An abbreviation for the Latin term "qua'que di'e", meaning every day.

q.h.: An abbreviation for the Latin term "qua'que ho'ra", meaning every hour.

q.i.d.: An abbreviation for the Latin term "qua'ter in di'e", meaning four times a day.

Rales (crackles): An ambiguous term used by doctors to describe an abnormal sound heard when listening for breath sounds during examination of the chest. It is used by some to denote a rhonchus and by others for crepitation. Such sounds are created when air moves through airways that contain fluid.

Residual Volume (RV): A pulmonary function test that measures the volume of air remaining in the lungs after maximum expiration.

Respiration: The process by which oxygen from the air is exchanged for carbon dioxide produced by the body. It includes the mechanical process of breathing, gas exchange in the lungs, and delivery of oxygen and carbon dioxide via the blood to the interstitial fluids and into and out of the cells.

Respiratory Distress Syndrome (RDS): A lung condition characterized by severe respiratory insufficiency/failure associated with pulmonary infiltrates chest x-ray, impaired oxygen absorption, and the absence of elevated pulmonary arterial hypertension. The condition can occur in children and adults (ARDS) and can arise from a variety of pulmonary and other insults. A similar disease called hyaline membrane disease also occur in premature infants born before the lungs have matured to the point where they are able to produce adequate amounts of surfactant to prevent lung collapse. In all forms, severe breathlessness is characteristic and rapidly decompensates to respiratory failure with hypoxemia and cyanosis requiring mechanical ventilation for survival.

Respiratory Failure: Inability of the lungs to conduct gas exchange.

Respiratory Quotient: The ratio of the volume of carbon dioxide expired to the volume of oxygen absorbed by the lungs per unit of time.

Rhonchi: A specific term used to denote an abnormal sound with a musical pitch occurring during inspiration or expiration, heard when listening to breath sounds during examination of the chest. Rhonchi are caused by air passing through airways (bronchi) that are narrowed by inflammation, spasm of smooth muscle, or presence of mucous in the lumen. Low pitched rhonchi are called sonorous rhonchi and high pitched whistling or squeaking rhonchi are referred to as sibilant rhonchi.

Risk Factors: Any genetic trait, medical condition, specific behavior or environmental exposure that is associated with an increased chance (risk) of an individual developing a disease.

Sign: Any abnormality indicative of a disease, discoverable on examination of the patient, i.e., an objective indication of disease.

Spirometry: A set of pulmonary functions tests that are performed by breathing into an instrument called a spirometer, which records the amount and rate of air that is inhaled and exhaled. Some of the test measurements are obtained by normal breathing, and other tests require forced inhalation and/or exhalation.

Sputum: Expectorated material usually consisting mostly of mucous or mucous mixed with pus. It is frequently produced in increased amounts in diseases of the airways, i.e.,chronic bronchitis or cystic fibrosis.

Streptococcus pneumoniae (pneumococcus): A specific type of bacteria, which is the most common cause of pneumonia in humans. Pneumococcus causes death from pneumonia in approximately 40,000 individuals in the United States each year. The pneumococcal vaccine helps prevent pneumococcus-related pneumonia and death.

Surfactant: A whitish milky substance consisting of lipids and proteins that are secreted by type II alveolar epithelial cells that line the alveoli. It consists of 90% lipids (mostly phospholipids) and 10% proteins. There are four main surfactant proteins: surfactant protein-A (SP-A), SP-B, SP-C, and SP-C. SP-B and SP-C are very lipid-soluble and serve critical role in a mechanism which prevents the alveoli from collapsing at the end of a breath. SP-A and SP-D are more water-soluble and appear to have important roles in lung host defense.

Symptom: Any phenomenon or departure from the normal in structure, function, or sensation experienced by the patient that indicates the presence of a disease, i.e., a subjective indication of disease.

Symptomatic Treatment: A therapy that reduces the symptoms of a disease without specifically reducing or eliminating the cause.

t.i.d.: An abbreviation for the Latin term "ter in di'e", meaning three times a day.

Thoracentesis: Removal of fluid from the pleural cavity, usually with a thin metal or plastic needle inserted between the ribs.

Tidal Volume (VT): A pulmonary function test that measures the volume of air inspired or expired with each breath during quiet breathing.

Total Lung Capacity (TLC): A pulmonary function test that measures the volume of air inside the lung after maximum inspiration .

Trachea: The air tube extending from the larynx into the thorax where it bifurcates (splits) into the right and left mainstem bronchi.

Ultrasound: Mechanical radiant energy with a frequency greater than 20,000 cycles per second.

Ultraviolet: Electromagnetic radiation (light) with wavelengths between the violet end of the visible spectrum and the range characteristic of rays or radiation used to create roentgens (x-ray images of the body).

Vaccination: The act of administering a vaccine.

Vaccine: A drug made from a killed preparation of a specific viral or bacterial pathogen that stimulates a person's immune system to develop specific antibodies that can recognize and prevent infection by the organism upon subsequent exposure.

Ventilation: The process by which air (or other gases) are moved into and out of the lungs.

Ventilator: An apparatus for administering artificial respiration in cases of respiratory failure. It is also known as a respirator.

Vital Capacity (VC): A pulmonary function test that measures the maximum volume of air expired from the point of maximum inspiration.

Wheezing: A raspy or whistling sound heard when someone takes a breath in or out. It may be a sign of airway constriction of obstruction.

Xanthoma: A papule, nodule, or plaque of a yellow color in the skin, due to deposits of lipids. They may be an indication of elevated levels of lipids in the blood or a familial disorder of cholesterol metabolism.

Xenobiotic: A chemical foreign to the biological system of an individual.

X-linked: Inheritance of a gene or genetic trait on the X chromosome; in other words, sex-linked.