12 Minute Walk - Amyotropic Lateral Sclerosis

12-minute walk usually a part of a pulmonary rehabilitation program, performed once a day for the duration of the program. The objective is for each patient to walk on a flat, smooth surface as far as possible during the 12 minutes, stopping as necessary and quantifying the total distance covered

a/A ratio the ratio of arterial-to-alveolar oxygen partial pressures (Pao2/PAO2); a measure of the efficiency of oxygen transfer across the lung

AARC abbreviation for the American Association for Respiratory Care, which is the primary voluntary professional association for respiratory care practitioners

AARC Code of Ethics professional policy document that describes the ethical behaviors for respiratory therapists to guide professional practice.

ABCD survey primary patient assessment/treatment steps to be taken in emergency or resuscitation situations, including Airway, Breathing, Circulation, and Defibrillation, focusing on basic CPR and defibrillation. Time drives all aspects of emergency cardiovascular care (ECC), and important preliminary first actions such as assessing unresponsiveness and calling for help are performed just before the "A" (airway) of the primary ABCD survey.

abciximab a platelet GP IIb/IIIa receptor inhibitor that blocks the GP IIb/IIIa receptors on activated platelets from binding to vWF and fibrinogen, thus inhibiting platelet adhesion and aggregation and further thrombus formation.

ABCs Airway, breathing, and circulation. The determination of unresponsiveness, breathlessness, and pulselessness and their management.

abdominal muscles muscles in addition to those directly involved in respiration that nevertheless aid in expiration, including the rectus abdominis, external and internal oblique muscles, and the transversus abdominis muscles, which depress the lower ribs, increase intraabdominal pressure, and flex the thoracic spine.

abdominal paradox an abnormal breathing pattern seen as a sinking inward motion of the abdomen with each inspiratory effort; a sign of diaphragm fatigue

abduct to draw away from the median plane of the body or from one of its parts.  

aberrancy see Aberrant ventricular conduction (aberrancy).

aberrant ventricular conduction (aberrancy) an electrical impulse originating in the SA node, atria, or AV junction that is temporarily conducted abnormally through the bundle branches, resulting in a bundle branch block. This is usually caused by the appearance of the electrical impulse at the bundle branches prematurely, before the bundle branches have been sufficiently repolarized. Aberrancy may occur with atrial fibrillation, atrial flutter, premature atrial and junctional contractions, and sinus, atrial, and junctional tachycardias. Also referred to simply as ventricular aberrancy.

abruptio placentae detachment of the placenta from the uterus before birth; often results in severe bleeding

abscess a localized collection of pus surrounded by swollen tissue

absolute humidity the actual amount of water vapor in a gas.

absolute refractory period (ARP) of the ventricles the period of ventricular depolarization and most of ventricular repolarization during which the ventricles cannot be stimulated to depolarize. It begins with the onset of the QRS complex and ends at about the peak of the T wave.

absolute shunt the sum of the anatomic and capillary shunts is referred to as true or absolute shunt. Absolute shunting is refractory to oxygen therapy.

absolute zero the temperature at which no molecular motion occurs, -273° Celsius, 0 Kelvin.

absorption atelectasis alveolar collapse that results from alveolar gas absorption into the pulmonary capillaries. It is more likely to occur in subjects who are breathing high concentrations of oxygen or have airway obstruction to the affected alveoli.

A/C alternative abbreviation for assist/control ventilation; see assist/control

accelerating waveform a pressure or flow to time tracing that indicates an upward or increasing movement (acceleration) of the pressure or flow value over time.

accelerated idioventricular rhythm (AIVR) an arrhythmia originating in an ectopic pacemaker in the ventricles with a rate between 40 and 100 beats per minute. Also referred to as accelerated ventricular rhythm, idioventricular tachycardia, and slow ventricular tachycardia.

accelerated junctional rhythm an arrhythmia originating in an ectopic pacemaker in the AV junction, with a rate between 60 and 100 beats per minute.

accelerated rhythm three or more consecutive beats originating in an ectopic pacemaker with a rate faster than the inherent rate of the escape pacemaker but less than 100 beats per minute. Examples are accelerated junctional rhythm and accelerated idioventricular rhythm (ANR).

accelerated ventricular rhythm See Accelerated idioventricular rhythm (AIVR).

accessory conduction pathways several distinct abnormal electrical conduction pathways within the heart that bypass the AV node, the bundle of His, or both, thus allowing the electrical impulses to travel from the atria to the ventricles more rapidly than usual. They include the accessory atrioventricular (A V) pathways (the bundles of Kent), the atrio­His fibers, and the nodoventricular/fasciculoventricular fibers.

accessory atrioventricular (AV) pathways (bundles of Kent) abnormal accessory conduction pathways located between the atria and the ventricles that bypass the AV junction, resulting in the so-called Wolff-Parkinson-White (WPW) conduction. The result is an abnormally wide QRS complex with a delta wave and an abnormally short PR interval, the classic form of ventricular preexcitation. When this type of AV conduction is associated with a paroxysmal supraventricular tachycardia with normal QRS complexes, it is known as the Wolff-Parkinson-White (WPW) syndrome. Three separate accessory AV pathways have been found: type A WPW conduction pathway, type B WPW conduction pathway, and posteroseptal WPW conduction pathway.

accessory AV pathway conduction see Accessory atrioventricular (AV) pathways (bundles of Kent).

accumulator a device that allows a volume of gas to be held for a period and that then releases the gas at a preset rate. Used as a timing or "limiting" mechanism.

acetylcholine a chemical found in most organs and tissues. Acetylcholine plays an important role in the transmission of parasympathetic nerve impulses at the synapses.   

accessory muscles muscles outside the principal respiratory muscles that nevertheless affect inspiration, including the pectoralis minor and major (innervated by C5-C8 and T1), the serratus anterior (innervated by C5-C7), and the erector spinae, which all help raise ribs, push the sternum forward and upward, and straighten the concavity of the thoracic spine.

acclimatization physiological or psychological adjustment to a new environment.

ACCP abbreviation for the American College of Chest Physicians

accreditation voluntary process intended to help establish and maintain the standards and expectations for all allied health education programs; although this is voluntary, the National Board for Respiratory Care requires graduation from an accredited educational program for eligibility for its credentialing examinations for individual professionals.

acetazolamide a carbonic anhydrase inhibitor with diuretic properties; inhibits formation of carbonic acid in the proximal tubules of the kidneys, thereby promoting elimination of sodium, potassium, bicarbonate, and water; prolonged use can cause an alkaline diuresis leading to metabolic acidosis

acetylcholinesterase an enzyme that inactivates the neurotransmitter acetylcholine by hydrolyzing the substance to choline and acetate

acetylcysteine a mucolytic agent that lowers the viscosity of mucoid secretions by chemically disrupting the sulfhydryl bonds of mucopolysaccharides

acid compound that donates or yields a hydrogen ion (H+) in an aqueous solution; a substance that donates a proton in a proton-transfer reaction.

acidemia decreased pH and increased hydrogen ion concentration of the blood.

acid-fast of or pertaining to a bacterial stain that does not decolorize easily when washed with an acid solution; also refers to certain bacteria (especially Mycobacteria), which retain red dyes after an acid wash

acidosis pathologic condition resulting from the accumulation of acid in, or loss of base from, the body.

acid-fast bacilli (AFB) bacteria in which the cell wall, because of the presence of waxes such as mycolic acid, retains red carbolfuschin stain despite rinsing with hydrochloric acid, making these bacteria acid-fast; acid-fast bacteria are considered neither gram-positive nor gram­negative.

acid-maltase deficiency type II glycogen storage disease that arises because of a deficiency of the lysosomal enzyme responsible for the hydrolysis of the glycogen.

aciduria the presence of a greater-than-normal hydrogen ion concentration in the urine (normal urine pH ranges from 4.6 to 8.0, with an average value of 6.0)

acinus (pl.: acini) the smallest division of a gland; a group of secretory cells surrounding a cavity. The functional part of an organ. The respiratory acinus includes the respiratory bronchioles, alveolar ducts, alveoli, and all other structures within the acinus.

acquired immune deficiency syndrome (AIDS) an immune disorder caused by infection with the human immunodeficiency virus (HIV); HIV directly attacks the T-lymphocytes and T-helper cells of the immune system, thereby compromising both cell-mediated and humoral (antibody) immunity

acromegaly a chronic metabolic condition characterized by a gradual, marked enlargement and elongation of the bones of the face, jaw, and extremities

acromion process lateral portion of the spine of the scapula that forms the point of the shoulder. It articulates with the clavicle and gives attachment to the deltoid and trapezius muscles.

ACTH abbreviation for adrenocorticotropic hormone; a pituitary hormone that stimulates the adrenal cortex

actin one of the contractile protein filaments in myofibrils that give the myocardial cells the property of contractility. The other is myosin.

actinomycosis a chronic, systemic fungal disease caused by infection with organisms of the genus Actinomyces; most commonly affects the skin but can involve the lungs and other organ systems

action potentials electrical currents that travel across the cell membranes of the heart. The electrical events of an action potential are identical in skeletal muscles, cardiac muscles, and neurons. There are five phases of the action potential: phase a (depolarization), phase 1 (initial repolarization), phase 2 (plateau), phase 3 (final rapid depolarization), and phase 4 (resting or polar­ized state).

activase trade name for alteplase (t-PA), a thrombolytic agent.       .

activated partial thromboplastin time (APTT) direct way of evaluating overall coagulation status; used to assess the intrinsic clotting pathway, especially the early stages involving factors XII, XI, IX and VIII; often used for monitoring patients on heparin therapy.

active cycle of breathing breathing maneuver that combines breathing control, thoracic expansion control, and forced expiration technique.

active humidification humidification system in which energy (heat) is used to add water to the inspired gas.

active transport the movement of molecules across membranes in a direction opposite that expected due to diffusion or osmotic pressure

activities of daily living (ADL) a quantifiable measure of an individual's ability to perform common tasks associated with independent functioning

acute sharp, severe; of rapid onset and characterized by severe symptoms and a short course; not chronic.

acute abdomen an abdominal condition of sudden onset, accompanied by pain from intra­abdominal inflammation or infection

acute coronary syndromes include silent ischemia, stable and unstable angina, acute MI, and sudden cardiac death.

acute exacerbation sudden worsening of respiratory symptoms accompanied by deteriorating lung function; most often, patients will present with increased dyspnea, cough, and changes in the quality or quantity of sputum.

acute lung injury (ALl) respiratory disorder characterized by the abrupt onset of respiratory distress; associated with severe hypoxemia and diffuse pulmonary opacities on chest radiograph (CXR) that are not caused by congestive heart failure or volume overload.

acute myocardial infarction (acute MI, AMI) a condition that is present when necrosis of the myocardium occurs because of prolonged and complete interruption of blood flow to the area. The area of the myocardium involved identifies the acute myocardial infarction:

•   Anterior MI

•   Septal MI

•   Anterior (localized) MI Anteroseptal MI

•   Inferior (diaphragmatic) MI Inferolateral MI

•   Lateral MI Anterolateral MI Extensive anterior MI

•   Posterior MI

•   Right ventricular MI

acute respiratory distress syndrome (ARDS) respiratory disorder characterized by fulminant pulmonary interstitial and alveolar edema, respiratory insufficiency, and hypoxemia.

ACV alternative abbreviation for assist/control ventilation; see assist/control

A-D (analog/digital) converter a device that converts a DC analog electrical signal to the form of digital data that can be managed by a computer. This permits the computer to use the electrical data signal from a measuring device.

Adams-Stokes syndrome sudden attacks of unconsciousness, with or without convulsions, caused by a sudden slowing or stopping of the heart beat.

Addison's disease a life-threatening condition caused by partial or complete failure of adrenocortical function, often resulting from autoimmune processes, infection (especially tubercular or fungal), neoplasm, or hemorrhage in the gland

adduct to move a limb toward the axis of the body

adenocarcinoma anyone of a large group of malignant, epithelial cell tumors.

adenoma a benign neoplasm in which cells are derived from glandular epithelium

adenopathy any enlargement of a gland, especially a lymphatic gland

adenosarcoma a cancerous gland-like tumor, such as Wilms' tumor

adenosine an antiarrhythmic used to convert paroxysmal supraventricular tachycardia (PSVT) with narrow QRS complexes and narrow-QRS-complex tachycardia of unknown origin (with pulse).

adenosine diphosphate (ADP) a substance released from platelets after the platelets are activated following damage to the blood vessel walls. Adenosine diphosphate promotes thrombus formation by stimulating platelet aggregation. Other substances released on platelet activation are serotonin and thromboxane A2.

adenosine triphosphate (ATP) high-energy triphosphate that is the main molecule used to store energy; supplies energy directly to the energy-using reactions of all cells in all kinds of living organisms.

adenovirus anyone of the 33 medium-sized viruses of the Adenoviridae family, pathogenic to humans, that cause conjunctivitis, upper respiratory infection, or gastrointestinal infection

ADH abbreviation for antidiuretic hormone; a hormone stored and released by the posterior lobe of the pituitary gland that stimulates the reabsorption of water by the renal tubular epithelial cells; due to mild vasopressor effects ADH is also called vasopressin

adjustable reducing valve a valve that allows the user to determine (adjust) the pressure limits.

adjustable restrictor a mechanism that governs flow or pressure by use of a series of variable-sized orifices.

adjuvant substance, especially a drug, added to a prescription to assist in the action of the main ingredient; also, an additional treatment or therapy.

ADL abbreviation for activities of daily living; a quantifiable measure of an individual's ability to perform common tasks associated with independent functioning

adrenalin trade name for epinephrine. See epinephrine. Adrenergic Having the characteristics of the sympathetic nervous system; sympathomimetic.

adrenergic of or pertaining to the sympathetic nerve fibers of the autonomic nervous system that use epinephrine or epinephrine-like substances as neurotransmitters; any chemical or drug that mimics the effect of these neurotransmitters. Also called sympathomimetic drug; catecholamine

adrenergic receptor site in a sympathetic effector cell that reacts to adrenergic stimulation.

adrenocorticosteroid (also corticosteroid) a broad term referring to any of the steroid hormones produced by the adrenal cortex, including their synthetic equivalents; major categories include the glucocorticoids (for example, hydrocortisone), the mineralocorticoids (for example aldosterone), and the androgens

adsorption ability to hold substances to a surface.

adult respiratory distress syndrome (ARDS) a pattern of clinical physiological and pathological features characterizing the lung's response to a variety of injuries and resulting in diffuse damage to the alveolar-capillary membrane

advance directive document to be used on the patient's behalf, in the absence of competency, specifying what treatments a patient does or does not want in such a case and sometimes, in some states, specifying a surrogate to make decisions in the event that the patient cannot (see medical power of attorney).

advanced cardiac life support (ACLS) post-arrest treatment after a cardiac arrest; includes (1) maintaining the airway with equipment and advanced techniques, (2) monitoring electrocardiogram (ECG) and recognizing dysrhythmias, (3) using conventional defibrillators, (4) administration of supplemental oxygen and drugs via parenteral or endotracheal routes.

advanced life support emergency medical care beyond basic life support, including one or more of the following: starting an intravenous (IV) line, administering IV fluids, administering drugs, defibrillating, inserting an esophageal obturator airway or endotracheal tube, and monitoring and interpreting the ECG.

adventitious lung sounds abnormal lung sounds superimposed on the basic underlying breath sounds

aerobe free-living organism that requires oxygen for survival.

aerobic pertaining to the presence of air or oxygen.

aerobic exercise any physical activity that requires increased cardiac output and ventilation to meet the increased oxygen demands of the skeletal muscles

aerosol a suspension of solid or liquid particles in a gas.

aerosol density (particulate) the number of aerosol particles per unit of carrier gas

aerosol density (weight) the actual weight of aerosol carried in a given volume of gas in milligrams of aerosol per liter (mg/L)

aerosol output the weight or mass of aerosol particles produced by a nebulizer per unit time or volume

AFB abbreviation for acid-fast bacillus, especially Mycobacteria that retain red dyes after an acid wash

affective characteristics common traits, attributes, qualities, and abilities found in those who share a condition or pattern of behavior or thinking.

affective domain the area of emotion, mood, or feeling

afferent carrying impulses toward a center.

afferent nerves nerves that carry impulses from the periphery to the central nervous system.

affidavit a written statement of facts given voluntarily under oath

affinity attraction between two substances that, when united, form new substances (i.e., oxygen and hemoglobin form oxyhemoglobin).

afterdepolarization an abnormal condition of latent pacemaker and myocardial cells (nonpacemaker cells) in which spontaneous depolarization occurs because of a spontaneous and rhythmic increase in the level of phase 4 membrane action potential following a normal depolarization. If afterdepolarization occurs early in phase 4, it is called early afterdepolarization; if late in phase 4, it is called delayed afterdepolarization. This abnormal condition is also referred to as triggered activity.

afterload resistance in the circulation against which the ventricle must eject blood during contraction; the load that opposes myocardial shortening.

agammaglobulinemia a rare disorder characterized by the absence of the serum immunoglobulin, gamma globulin, associated with an increased susceptibility to infection

agglomeration the process of gathering together into a mass, as when many small aerosol particles come together to form a single large particle

agglutination the clumping of antigens with antibodies, or of the red blood cells from one type of blood to the red blood cells of another type

aggregation the coming together of substances, e.g., platelets, blood cells, diseases

aging (aerosol) the process in which aerosol particles change size due to evaporation or hygroscopic properties

agonal occurring at the moment of or just before death. Agonal rhythm Cardiac arrhythmia present in a dying heart. / Ventricular escape rhythm.

agonist agent that stimulates a receptor

agranulocytosis a condition of the blood marked by a sudden decrease in the number of granulocytes (a type of white blood cell); occurs in lesions of the throat or other mucous membranes or as a side effect of the administration of certain drugs or radiation

AHI abbreviation for the apnea-hypopnea index, used to quantify the severity of obstructive sleep apnea (OSA) and its response to treatment with CPAP

AIDS abbreviation for acquired immune deficiency syndrome

air bronchogram radiographic abnormality in the image of the bronchi occurring when the alveolar air spaces become filled with fluid, causing increased contrast between the air-filled bronchi and adjacent fluid-filled lung parenchyma, rendering the bronchi lucent and projecting them as branching tubular air-filled structures.

air-dilution adding air to a primary gas to reduce the oxygen concentration of the primary gas.

air-entrainment mask an oxygen mask that employs a Venturi or Pitot type of device to provide precise concentrations of high-flow oxygen to the patient.

air foil a device that acts like an airplane wing to generate pressure differences by creating areas of high and low resistance in an airstream.

air inlet regulator a regulator that determines the inlet pressure on a gas system or ventilator.

air stacking a technique used by some chronic neuromuscular disease patients to maximize lung insufflation, increase lung compliance, raise voice volume, or increase expiratory cough flows; performed by taking multiple consecutive breaths from a positive pressure ventilator

airborne precautions safeguards designed to reduce the risk of airborne transmission of infectious agents

airborne transmission transmission of infectious organisms via dissemination of the infectious agent in the air either by aerosol droplets, droplet nuclei, or dust particles

agranulocyte any leukocyte that does not contain predominant cytoplasmic granules, such as a monocyte or lymphocyte.

air liquefaction process by which air is made into a liquid. ,

air trapping condition in the lung in which air is not exhaled because of decreased lung elasticity and increased expiratory airway resistance; accompanied by hyperinflation.

air space disease condition characterized by parenchymal opacification, the silhouette sign, and air bronchograms.

airway conductance a measure of the ease with which gas flows through the respiratory tract; abbreviated as G, conductance is the reciprocal of airway resistance, that is, G = flow/change in pressure

airway hyperresponsiveness marker associated with asthma that is responsive to both specific and nonspecific factors (such as environment, exercise, allergens, and viral infections), whereby the airways constrict too easily and frequently.

airway inflammation condition that exacerbates asthmatic reactions by the release of mediators including mast cells, eosinophils, macrophages, epithelial cells, and T lymphocytes, resulting in recurrent exacerbations that manifest as wheezing, progressive shortness of breath, chest tightness, and coughing; may be classified as acute, subacute, or chronic.

airway occlusion pressure (Po.1) the inspiratory pressure generated 100 milliseconds after airway occlusion. Po.l is effort independent and is thought to be a good measure of central respiratory drive

airway pressure pressure achieved in the patient airway, usually measured at the distal end of the endotracheal tube.

airway pressure release ventilation (APRV) a mode of ventilation during which the patient breathes spontaneously at an elevated baseline that is periodically "released" to allow full expiration.

airways resistance (Raw) pressure difference developed per unit flow as gas flows into or out of the lungs; normally, 2.4 cm H2O/L/s at 0.5 L/s. Raw measurements can complement other tests evaluating airway responsiveness to bronchial provocation or bronchodilation.

alar nasi the wing-like lateral projections of the nose

albumin a protein compound normally found within human blood.

algorithm specific protocol that provides explicit rules for solving a health care problem.

ALI abbreviation for acute lung injury

alkalemia increased pH and decreased hydrogen ion concentration of the blood.

alkaloid anyone of a large group of alkaline organic chemicals found in plants that exert powerful physiological activity; examples include morphine, cocaine, nicotine, and atropine

alkalosis an abnormal physiological process resulting in a decrease in the hydrogen ion concentration in the body; may be caused by either an excess accumulation of base or the loss of acid

allegation a written statement by a party to a suit concerning what the party expects to prove

Allen's test test performed before radial arterial puncture or cannulation to ascertain adequate ulnar artery perfusion to the hand.

allergen common triggering mechanism for asthmatic reactions; can be indoor factors (that is, mold, animal dander, cleaning chemicals, cockroach antigen, dust mites) or outdoor factors (that is, noxious fumes, grass, and tree pollens).

allergy specific type of hypersensitivity reaction; in adverse drug reactions, this is defined as an immune-mediated hypersensitivity reaction, which may be an immediate-type reaction or a delayed-type hypersensitivity reaction.

allographic of or pertaining to a tissue graft or organ transplant between individuals of different genetic makeup

allopathic referring to the system of medicine whereby disease is treated by antagonistic therapy, such as an antibiotic to treat infection; more generally, the predominant system of medicine education in the United States

alpha 1-antitrypsin (AAT) plasma protein produced in the liver that inhibits trypsin and other proteolytic enzymes; deficiency is associated with the development of emphysema.

α-adrenergic receptor type of adrenergic receptor that acts in response to sympathomimetic stimuli.

alteplase (t-PA) a thrombolytic agent that converts plasminogen, a plasma protein, to plasmin, which in turn dissolves the fibrin binding the platelets together within a thrombus (fibrinolysis), causing the thrombus to break apart (thrombolysis). Trade name: Activase.

alternate site mechanical ventilation (ASMV) use of an artificial device to assist patient breathing at a location other than the hospital ICU-usually the home setting or a long-term care facility.

alternating current an electrical current that undergoes changes in either direction or polarity.

alveolar air equation an equation used in computing the efficiency of oxygen transfer in clinical practice; PA02 = FI02(PB - PH20) - (Paco2/ R)

alveolar-capillary membrane the tissue that separates air from blood in the lung; consists of alveolar epithelium, basement membrane, and capillary endothelium, along with their associated structures

alveolar macrophage a phagocytic cell commonly found in alveoli. These cells clear bacteria and other debris from rhe alveolar spaces

alveolarization the process of alveolar development from epithelial tissue

alveoli small sacs or outpouchings through which gas exchange takes place between alveolar gas and capillary blood; composed of Type I and Type II cells.

AMBU (Air-Mask-Bag-Unit) a type of manual resuscitator consisting of a pliable bag, a one-way valve system, and either a mask or artificial airway connector.

ambient of or referring to the surrounding environmental conditions

ambient compartment in the Bird Mark series the portion of the ventilator casing that is open to the environment, hence to ambient pressures.

amblyopia reduced vision in an eye without a detectable organic lesion

American Association for Respiratory Care (AARC) primary professional organization for respiratory care; the AARC and related organizations contribute to the scientific basis, governance, stature, and future growth of respiratory care; assists chartered affiliates in their efforts to pursue meaningful, nonrestrictive licensure and promotes the sequential functions of higher education: research, archiving, and dissemination of knowledge.

American Association of Inhalation Therapists (AAIT) organization formerly called the Inhalation Therapy Association (ITA) and now known as the American Association for Respiratory Care (AARC).

American Registry of Inhalation Therapists (ARIT) organization established to oversee the processing, registration, and maintenance of the registry. In 1974 the ARIT, Inc., and the AART Technician Certification Board merged to form the National Board for Respiratory Therapy.

American Respiratory Care Foundation (ARCF) trusteeship administering more than $20,000 annually in awards, education recognition, fellowships, and grants, as well as providing financial support of the AARC consensus and special proceedings conferences.

American Society for Testing and Materials (ASTM) a nongovernmental agency that establishes performance standards for various equipment and materials

American Standard Safety System one of three indexed safety systems for medical gases. This system uses a combination of the following factors specific for each gas or gas combination: diameter of the outlet, number of threads per inch, whether outlet has right-handed or left­handed threads, whether the threads are external or internal, the shape of the mating nipple on the corresponding regulator.

amino acid basic protein unit or building block of proteins; the basic structure of an amino acid consists of a carbon atom (called the alpha carbon) to which are bonded an amino group (NH2), a carboxyl group (COOH), a hydrogen atom, and a side chain that constitutes the unique and identifying characteristic of the amino acid.

ammeter a device containing a galvanometer that is designed for measuring the amount of electrical current flow in a circuit.

amnesia a loss of memory; inability to recall past experiences

amniocentesis the process of direct sampling and quantitative assessment of the amniotic fluid

amniotic fluid liquid produced by the fetal membranes and the fetus; it surrounds the fetus throughout pregnancy, usually totaling about 1000 mL at term.

amplitude the height of a waveform; usually indicates intensity.

amplitude (voltage) with respect to ECGs, the height or depth of a wave or complex measured in millimeters (mm).

amyloid a waxy, starch-like protein that tends to build up in tissues and organs in certain pathologic conditions

amyotrophic lateral sclerosis (ALS) progressive neurodegenerative disorder of both upper and lower motor neurons leading to a loss of skeletal muscle strength, including the respiratory muscles.

Anabolism - ATPS

anabolism synthesis process that assembles precursor molecules, such as amino acids, sugars, fatty acids, and nitrogenous bases into cell macromolecules such as proteins, polysaccharides, lipids, and nucleic acids.

anaerobe free-living organism that requires an absence of oxygen; thought to be a minor cause of community­acquired pneumonia but becomes increasingly important in nosocomial pneumonia and ventilator-associated pneumonia.

anaerobic threshold the point at which the level of exercise is greater than the ability of the cardiopulmonary system to provide a sufficient supply of oxygen to the muscles, causing anaerobic metabolism to ensue.

anaerobic bacterial pneumonia pneumonia, usually multimicrobial, caused by anaerobic pathogens such as Pepto­streptococcus spp., Bacteroides melaninogenicus,· Fusobacterium necrophorum, Bacteroides asaccharolyticus, Porphyromonas endodontalis, and Porphyromonas gingivalis.

analgesic pain reduction property, typically demonstrated in nonsteroidal antiinflammatory agents.

analog electrical signal an electrical current, used as a signal, that varies continuously, without break over a range of values. Often the signal range developed by pulmonary function testing equipment is between -5 and +5 volts.

analog to digital converter machine that samples an analog signal at short intervals and assigns a digit to the analog value at each time point; after transmission the digital information can be converted back to analog for display.

analogous similar in function but having a different origin or structure.

analyte any substance that is measured; the term is usually applied to a component of blood or other body fluid

anaphylaxis a severe systemic allergic response characterized by redness, itching, swelling, and water buildup (angioedema); in severe cases, life-threatening respiratory distress occurs and the blood pressure drops rapidly (anaphylactic shock)  

anastomosis joining of vessels, either naturally or surgically, to allow flow to other structures.

anemia disorder characterized by a decrease in hemoglobin in the blood to levels below the normal range.

anemic hypoxia a type of hypoxia in which the oxygen tension in the arterial blood is normal, but the oxygen-carrying capacity of the blood is inadequate. This form of hypoxia may develop from (1) a low amount of hemoglobin in the blood or (2) a deficiency in the ability of hemoglobin to carry oxygen, such as carbon monoxide poisoning.

anemometer an instrument for measuring the velocity of an airstream.

anergy lack of activity; an immunodeficient condition characterized by a lack of or diminished reaction to an antigen or group of antigens. This state may be seen in advanced tuberculosis and other serious infections, acquired immunodeficiency syndrome, and some malignancies

aneroid barometer (manometer) a pressure-measuring device that compares a reference pressure to the observed pressure using one of several methods.

aneroid manometer assist indicator (cycle indicator) a light that signals a pressure change in an aneroid manometer that indicates that the patient has generated a negative pressure (assist effort).

anesthesia, anesthetic partial or complete loss of sensation caused by injury, diseases, or the administration of an anesthetic agent

anesthetic drug or agent capable of producing a complete or partial loss of feeling.

aneurysm dilation of an artery (such as the aorta) or a chamber of the heart (such as the ventricle).

angina choking, crushing, painful feeling most often associated with cardiac pain caused by hypoxia of the myocardium.

angina pectoris paroxysmal chest pain, which often radiates to the arms and may be accompanied by a feeling of suffocation and impending death; the most common cause is a shortage of oxygen to the cardiac muscle linked with coronary artery disease

angioplasty repair of a narrowed blood vessel through surgery or other angiographic procedures

angiography the x-ray visualization of the internal anatomy of the heart and blood vessels after the intravascular introduction of radiopaque contrast medium

angiotensin-converting enzyme (ACE) an enzyme found on the surface of blood vessels in the lungs and other tissues with vasopressor action

angiotensin-converting enzyme inhibitors agents that inhibit angiotensin-converting enzyme (a potent vasoconstrictor) and promote relaxation of blood vessels

angle of Louis a slightly oblique angle where the manubrium articulates with the body of the sternum

animal studies use of animals for medical research to establish and study models or simulations of human disease.

anion negatively charged ion that is attracted to the positive electrode (anode) in electrolysis; negatively charged atom, molecule, or radical.

anion gap difference between the concentrations of serum cations and anions such that: anion gap = ([Na+] + [K+]) - ([HC03-] + CL-]). If the anion gap exceeds 12 mmol/L, excessive unmeasured anions are likely present. Because its concentration is normally low, [K+] is often omitted from this calculation.

ankylosing spondylitis a chronic inflammatory disease of unknown origin, first affecting the spine and adjacent structures and commonly leading to eventual fusion (ankylosis) of the involved joints

ankylosis immobility of a joint

anode the pole in an electrochemical cell that attracts negatively charged ions.

anomaly a broad term denoting any deviation from what is regarded as normal

anorexia, anorectic loss of appetite for food

anoxia deficiency of oxygen.

antagonist drug that blocks a receptor.

antecubital fossa the triangular area at the bend of the elbow; frequently used as the site for venipuncture and brachial artery blood sampling

antegrade (or anterograde) conduction conduction of the electrical impulse in a forward direction, that is, from the SA node or atria to the ventricles or from the AV junction to the ventricles.

anterior indicating the front of a structure or body surface relative to other body parts.

anterior leads leads I, aVL, and V1-V6

anterior (localized) MI a myocardial infarction commonly caused by occlusion of the diagonal arteries of the left anterior descending (LAD) coronary artery.

anterior MI a myocardial infarction caused by the occlusion of the left anterior descending (LAD) coronary artery or the left circumflex coronary artery or any of their branches, singly or in combination. Anterior MI includes septal, anterior (localized), anteroseptal, lateral, anterolateral, and extensive anterior myocardial infarctions.

anterior nares the opening to the nose

anterolateral situated in front and to one side or the other

anterolateral MI a myocardial infarction commonly caused by occlusion of the diagonal arteries of the left anterior descending (LAD) coronary artery alone or in conjunction with the anterolateral marginal artery of the left circumflex coronary artery.

anteroposterior from the front to the back of the body, commonly associated with the direction of the roentgenographic or x-ray beam (an "AP" exposure)

anteroseptal MI a myocardial infarction commonly caused by occlusion of the left anterior descending (LAD) coronary artery involving both the septal perforator and diagonal arteries.

anthropometry study of human body measurements and components, including measurement of height, weight, body mass index, mid-arm muscle circumference, skinfold thicknesses, and skeletal breadths.

antiarrhythmic of or pertaining to a procedure or substance that prevents, alleviates, or corrects an abnormal cardiac rhythm

antibiotic chemical substance capable of inhibiting the growth of, or killing, certain microorganisms but generally nontoxic enough to be used chemotherapeutically in the treatment of infectious diseases.

antibody protein substance that develops in response to and interacts with an antigen. The antigen-antibody reaction forms the basis of immunity.

anticholinergic class of bronchodilators that decreases both bronchial and upper airway secretions; pertains to a blockade of acetylcholine receptors that results in the inhibition of the transmission of parasympathetic nerve impulses; the drug functions by competing with the neurotransmitter acetylcholine for its receptor sites at synaptic junctions.

anticholinergic agent any agent that blocks the parasympathetic nerves; often used as bronchodilators, delivered by inhalation (for example, ipratropium bromide for chronic obstructive pulmonary disease, or COPD).

anticholinesterase any enzyme that counteracts the action of the choline esters

anticipating key skill used in critical thinking; involves the ability to think ahead and envision possible problems; sometimes referred to as "future think."

anticoagulant drug that blocks or delays blood coagulation, specifically the formation of a new blood clot (thrombus), allowing the existing thrombus to be slowly broken down by serum thrombolytic enzymes.

anticoagulation use of an agent that prevents or delays coagulation of the blood.

antiderivative indefinite integral, denoted by the fact that it produces a function rather than a number.

antiemetic substance or procedure that prevents or alleviates nausea or vomiting.

antigen substance that induces the formation of antibodies that interact specifically with it. The antigen-antibody reaction forms the basis for immunity.

antigen detection newer technique that, along with PCR, is applied to sputum samples to help in the rapid identification of pathogens that may be difficult to culture or pathogens scarcely growing due to prior antibiotic treatment; can be applied to sputum, serum, urine, and body fluids; most valuable in the diagnosis of difficult-to-culture organisms, such as M. pneumoniae, L. pneumophila, C. pneumoniae, and viral pneumonias. (See also polymerase chain reaction [PCR].)

antihistamine drug or substance capable of reducing the physiologic and pharmacologic effects of histamine, including a wide variety of drugs that block histamine receptors.

antiinflammatory of or pertaining to a substance or procedure that counteracts or reduces inflammation

antimicrobial drug or substance that kills microorganisms or inhibits their growth or replication.

antioxidant agent that inhibits oxidation of a substance when added to it; those such as beta-carotene, alpha­tocopherol (vitamin E), and ascorbic acid (vitamin C) can help prevent lipid peroxidation triggered by free radicals and can assist in the repair of tissue damaged by oxidative stress.

antiplatelet agent any compound or drug that inhibits platelet adhesion and aggregation and further thrombus formation. Includes aspirin and platelet GP IIb/IIIa receptor inhibitors such as abciximab and eptifibatide.

antipyretic fever-reducing agent.

antisepsis the destruction of pathogenic microorganisms existing in their vegetative state on living tissue

antiseptic tending to inhibit the growth and reproduction of microorganisms

antitoxin an antibody capable of neutralizing a specific toxin, for example, tetanus antitoxin

antitrypsin inhibitor of trypsin; may be deficient in persons with emphysema.

antitussive any drug that acts on the central and peripheral nervous systems to suppress the cough reflex.

anxiolytic sedative or minor tranquilizing agent used primarily to treat episodes of anxiety.

aorta the main trunk of the systemic arterial circulation, comprising four parts: the ascending aorta, the arch of the aorta, the thoracic portion of the descending aorta, and the abdominal portion of the descending aorta.

aortic dissection splitting of the media layer of the aorta, leading to the formation of a dissecting aneurysm.

aortic regurgitation backflow of blood from the aorta into the left ventricle; indicates an incompetent valve

aortic valve the one-way valve located between the left ventricle and the ascending aorta.

AP series an obsolete Bennett ventilator series used for IPPB administration. AP stood for Air compressor Powered.

aPEEP abbreviation for auto-PEEP (also iPEEP for intrinsic PEEP)

aperture opening or orifice.

apex top end or tip of a structure.

apex of the heart the pointed lower end of the heart formed by the pointed lower ends of the right and left ventricles.

Apgar score the evaluation of an infant's physical condition, usually performed 1 minute and 5 minutes after birth, based on a rating of five factors that reflect the infant's ability to adjust to extrauterine life

aphagia a condition characterized by the loss of the ability to swallow as a result of organic or psychological causes

aphasia a nerve defect that results in loss of speech

aphonia inability to produce normal speech sounds or loss of voice

aphthous ulcers recurrent painful canker sores in the mouth

apical of or pertaining to the summit or apex

apices the uppermost portions of the lungs

apnea absence of spontaneous respiration.

apnea alarm a system that warns that the patient is not breathing or being ventilated.

apnea-hypopnea index (AHI) a measure of the incidence of apneic episodes used to quantify the severity of obstructive sleep apnea (OSA) and its response to treatment with CPAP

apnea of infancy category or type of cessation of air flow in breathing in the full-term infant; resolution may be determined more by the maturation of the respiratory control center than an underlying disease process.

apnea of prematurity (AOP) category or type of cessation of airflow in breathing in the premature infant; resolution may be determined more by the maturation of the respiratory control center than an underlying disease process; prevalence is higher at lower gestational ages and may be the result of an immature respiratory control system manifested by frequent periodic breathing, a decreased ventilatory response to CO2, and a depression of respiration produced by hypoxemia.

apneustic breathing a pattern of respirations characterized by a prolonged inspiratory phase followed by expiratory apnea

apneustic center a portion of the pontine respiratory centers that influence the respiratory components of the medulla. If unrestrained, the apneustic center continually sends neural impulses to the ventral respiratory group and dorsal respiratory group in the medulla.

apneustic flow time a reference to a control on the old Bird Mark series ventilators that limited the length of apnea or no flow allowed by the ventilator.

apparent life threatening event (ALTE) one of several most frequently diagnosed breathing disorders that call for home monitoring, including apnea of prematurity, sudden infant death syndrome, and GER.

APRV abbreviation for airway pressure release ventilation; a form of pressure-controlled synchronized intermittent mandatory ventilation (SIMV)

ARCF abbreviation for the American Respiratory Care Foundation; a philanthropic agency that promotes the field of respiratory care through grants and awards

ARDS acute (or adult) respiratory distress syndrome.

arousal index value derived from the data gathered during the polysomnogram: the number of arousals divided by the total sleep time, expressed in arousals/hour, which normally should be less than 15.

arrhythmia a rhythm other than a normal sinus rhythm when (1) the heart rate is less than 60 or greater than 100 beats per minute, (2) the rhythm is irregular, (3) premature contractions occur, or (4) the normal progression of the electrical impulse through the electrical conduction system is blocked. Also known as dysrhythmia, a more appropriate term but one not used as frequently.

arterial blood gas blood component whose primary measurements (Po2, Pco2, and pH) provide important information about oxygenation, ventilation, and acid-base status and also guide respiratory and metabolic interventions.

arterial pertaining to one artery or a network of arteries.

arterial blood pressure one of the four vital signs; monitoring techniques range from intermittent manual determinations using sphygmomanometry to automated noninvasive devices and indwelling arterial cannulae, providing continuous pressure measurements and waveform graphics.

arterial gas embolism disease that occurs from pulmonary over-pressurization; if the pressure in the lungs exceeds the integrity of the lung parenchyma, the lung will tear and the air escapes into either the pleura, resulting in a pneumothorax; into the mediastinum, resulting in pneumomediastinum or subcutaneous emphysema; or, in the worst scenario, into pulmonary vessels, carrying air into the heart.

arterialized capillary blood tissue capillary blood that is made to have blood gas values similar to arterial blood. Arterialization is accomplished by heating the tissue site, which causes arteriolar dilation and increases tissue capillary perfusion (hyperemia).

arteriography a method of radiologic visualization of arteries performed after a radiopaque contrast medium is introduced into the bloodstream or into a specific vessel by injection or through a catheter

arteriole a very small artery, especially one that, at its distal end, leads into a capillary.

arteriolar constriction arterioles are the last arterial vessels through which blood passes before entering the tissue capillary beds. Contraction of the smooth muscle tissue in the walls of arterioles causes constriction of the vessels. The use of varying degrees of constriction is the basis for controlling the rate of blood flow to a particular tissue capillary bed.

arteriolized blood blood that has been fully oxygenated by passage through the lungs

arteriosclerosis a common arterial disorder characterized by thickening, loss of elasticity, and calcification of arterial walls, resulting in a decreased blood supply.

arteriovenous anastomosis a communication between an artery and a vein, either as a congenital anomaly or as a surgically produced link between vessels

arteriovenous shunt a passageway, artificial or natural, that allows blood to flow from an artery to a vein without going through a capillary network.

artery one of the large blood vessels carrying blood in a direction away from the heart.

arthrodesis the immobilization of a joint accomplished surgically

arthroplasty surgical reconstruction or replacement of a diseased joint

artifacts mechanically or electrically produced extraneous spikes and waves recorded on an ECG record. Common causes of artifacts are muscle tremor, alternating current (AC) interference, loose electrodes, interference related to biotelemetry, and external chest compression. Artifacts are also referred to as electrical interference or noise.

artificial nose passive humidifier, also known as a heat and moisture exchanger (HME) , that captures exhaled heat and moisture and transfers part of that heat and humidity to the next inspired breath; can include condensers, hygroscopic condensers, and hygrophobic condensers.

artificial pacemaker an electronic device used to stimulate the heart to beat when the electrical conduction system of the heart malfunctions, causing bradycardia or ventricular asystole. An artificial pacemaker consists of an electronic pulse generator, a battery, and a wire lead that senses the electrical activity of the heart and delivers electrical impulses to the atria or ventricles or both when the pacemaker senses an absence of electrical activity.

asbestosis a restrictive lung disease caused by prolonged exposure to asbestosis fibers; associated with a high incidence of malignant lung tumors and pleural abnormalities

ascites accumulation of fluid in the abdomen

asepsis the absence of pathogenic microorganisms; the removal of pathogenic microorganisms or infected material

aspergillosis an infection caused by a fungus of the genus Aspergillus, capable of causing inflammatory, granulomatous lesions on or in any organ

asphyxia condition caused by an insufficient uptake of oxygen.

aspirate (verb) to withdraw fluid by negative pressure; (noun) the fluid so withdrawn

aspiration the act of inhaling. Pathologic aspiration of vomitus or other foreign substances into the respiratory tract.

aspiration pneumonia an inflammatory condition of the lungs and bronchi caused by the inhalation of foreign material or vomitus containing acid gastric contents.

aspirin an antiplatelet agent.

assist and sensitivity mechanism a device that sets the maximum effort a patient must make (sensitivity) before the ventilator cycles on (assists).

assist/control (A/C or ACV) continuous mandatory ventilation (CMV) in which the minimum breathing rate is predetermined, but the patient can initiate ventilation at an increased rate

assisted inspiration externally applied transrespiratory pressure change acting in synchrony with muscle pressure (if present) to increase tidal volume and flow.

assisted ventilation a ventilator's function, occurring whenever airway pressure (that is, ventilator pressure) rises above baseline during inspiration; thus the breath is said to be assisted, independent of other breath characteristics (that is, whether the breath is classified as spontaneous or mandatory); not to be confused with the meaning of the word assist in specific names of modes of ventilation (for example, assist/control mode) sometimes used by ventilator manufacturers for modes without regard to consistency or theoretical relevance.

assistor a ventilator that allows the patient to initiate inspiration.

assist transducer a device that converts a patient's inspiratory effort (negative pressure signal) to an electric current that in turn initiates inspiration.

ASSS abbreviation for American Standard Safety System; specifications adopted in the United States and Canada for threaded high-pressure connections between compressed gas cylinders and their attachments

asthma chronic inflammatory disorder of the airways in which many cells and cellular elements playa role in particular, mast cells, eosinophils, T lymphocytes, macrophages, neutrophils, and epithelial cells; causes recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particular at night or in the early morning.

asthma education program plan implemented by clinicians to ensure patient and caregiver compliance, thereby minimizing exacerbations and health care costs by providing maximum understanding of current asthma treatment and management.