Tachycardia-Tomography

tachycardia an abnormal circulatory condition in which the myocardium contracts regularly but at a rate of greater than 100 beats per minute.

tachyphylaxis a phenomenon in which the repeated administration of some drugs results in a marked decrease in effectiveness

tachypnea a rapid rate of breathing.

tactile fremitus palpation of vibrations of the chest wall as a patient speaks.

tamponade stoppage of the flow of blood to an organ or a part of the body by pressure, as by a tampon or a pressure dressing applied to stop a hemorrhage or by compression of a part by an accumulation of fluid, as in cardiac tamponade

tank ventilator another name for an iron lung.

Ta wave atrial T wave; usually buried in the following QRS complex.

T axis the mean of all the vectors generated during the repolarization of the ventricles (i.e., during the T wave).

target heart rate the heart rate achieved at 65% of a patient's maximum oxygen consumption during the exercise evaluation, used for aerobic conditioning

Taylor dispersion augmented diffusion of gas in situations of parabolic gas flow, resulting in high energy spikes; this augmented diffusion process is facilitated by the increased surface area between two gas streams during HFV. 

TDP abbreviation for therapist-driven protocol, a specification of actions that allow RCPs to independently initiate and adjust therapy, within guidelines previously established by medical staff

teaching moment any opportunity to impart critical and meaningful information to a captive audience.

technetium a metallic, radioactive, synthetic chemical element with an atomic weight of 99; symbol Tc.

telemetry data transmission to a remote location; measurement at a distance.

teleologic theory ethical theory that guides decision making regarding the right or wrong qualities of an action based on consequences of predicted outcomes.

temperature a measure of molecular activity or motion. Also a reference to the reactive hotness or coldness of a material.

temporary transvenous pacemaker delivery of electrical impulses generated by an external artificial pacemaker through a catheter threaded through a vein and positioned in the right ventricle.

tenecteplase (TNK-tPA) 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: TNKase.

tension pneumothorax air in the pleural space that exceeds atmospheric pressure causing outward expansion of the ribs, downward depression of the diaphragm, mediastinal shift, and hypotension

tension-time index the product of contractile force (ratio of diaphragmatic pressure to maximum diaphragmatic pressure) and contractile duration (ratio of inspiratory time to total breathing cycle time)

term pertaining to an infant born between 38 to 42 weeks gestation

terminal the final wave of the QRS complex.

terminal Rand S waves typical ECG findings in right bundle branch block-tall "terminal" R waves in leads aVR and V1-V2; deep and slurred "terminal" S waves in leads I, aVL, and V5-V6

tetany hyperexcitability of nerves and muscles due to low serum calcium levels; a syndrome characterized by intermittent tonic spasms of the extremities, cramps, and convulsions

tetralogy of Fallot congenital cardiac anomaly, consisting of four defects: ventral septal defect, an overriding of the ascending aorta, obstruction of the right ventricular 'outflow tract, and right ventricular hypertrophy.

tetraplegia paralysis of all four limbs; quadriplegia.

thallium scan a cardiac stress test using intravenous thallium injection to diagnose ischemia and coronary artery disease

therapeutic index the difference between the minimum therapeutic and minimum toxic concentrations of a drug

therapeutic positioning application of gravity to achieve specific clinical objectives, including mobilization of secretions (postural drainage), improving the distribution of ventilation (dependent positioning), and relieving dyspnea (relaxation positioning)

therapeutic window range of drug concentration bounded on the low side by the minimum effective concentration and on the high side by the onset of dose-related side effects.

therapist-driven protocol a specification of actions that allow respiratory care practitioners to independently initiate and adjust therapy, within guidelines previously established by medical staff; also called respiratory care protocol

thermal conductivity the physical ability of a substance to conduct heat: the principle is used in oxygen analyzers and flow sensors.

thermistor thermometer that can measure extremely small changes in temperature.

thermocouple apparatus that detects bidirectional airflow at the nose and mouth by sensing the temperature difference between inspired room air and exhaled air that has been warmed to body temperature; an active sensor used to measure temperature.

thermodilution method of measuring cardiac output by injecting a cold or cool indicator and sampling with a thermistor.

thermodilution cardiac output determination a procedure in which, through use of a pulmonary artery catheter (Swan-Ganz type), a bolus of isotonic saline (approximately 10 ml) at a known temperature (e.g., 0°C) is injected into the right atrium. A distal temperature sensory in the catheter's tip (in the pulmonary artery) measures the rate of blood temperature change that occurs after the injection. The rate of temperature change is interpreted by computer as an indicator of cardiac output (i.e., a fast rate of cooling and the rewarming of blood at the sensor would indicate a greater rate of cardiac output). The computer gives a numerical value for cardiac output and, if given a value for the subject's body surface area, can provide a value for cardiac index.

third-degree AV block (complete AV block) complete absence of conduction of electrical impulses from the atria to the ventricles through the AV junction. May be transient and reversible or permanent (chronic). Usually associated with abnormally wide QRS complexes, but the QRS complexes may be narrow. See AV block, third-degree.

3-second interval the period between two adjacent 3-second interval lines.

thoracentesis the surgical perforation of the chest wall and pleural space with a needle for diagnostic or therapeutic purposes or for the removal of a specimen for biopsy

thoracic computed tomography a radiographic technique that produces a cross-sectional view of the chest structures, with the ability to detect subtle changes in density

thoracolumbar relating to the thoracic and lumbar portions of the vertebral column.

thoracotomy a surgical opening into the thoracic cavity

thorax lungs, pleura, respiratory muscles, and skeletal elements, including the sternum, ribs, thoracic vertebrae, the clavicles, and the scapulae; within the thorax, the mediastinum contains major blood vessels, the esophagus, and the heart enveloped within the pericardial sac.

Thorpe tube flow control device that provides an accurate display of flow, provided it is in a vertical position and the inlet pressure is constant. Unlike flow restrictors and Bourdon gauges, pressure-compensated Thorpe tube flow meters display the actual outlet flow in the face of downstream resistance.

Thorpe-tube/reducing valve regulator a combination of a pressure reducing valve and a Thorpe tube-type flowmeter that can regulate both pressure and flow.

three-way exhalation valve solenoid an electronic device that determines the direction of flow in an expiratory valve.

threshold potential the value of intracellular negativity at which point a cardiac cell can be depolarized after being electrically stimulated.

threshold resistance usually the amount of pressure needed to overcome resistance to flow.

threshold response pertaining to a physiological action caused by the minimum stimulus needed to provoke it thrill a fine palpable vibration felt accompanying a cardiac or vascular murmur

thrill vibration felt on palpation, especially over the heart

thrombin an enzyme formed from prothrombin when prothrombin is exposed to tissue factor released from damaged arterial wall tissue. Thrombin in turn converts fibrinogen to fibrin.

thrombocyte a membranous sac enclosing a thrombus.

thrombocytopenia reduced number of thrombocytes (platelets)

thrombolysis the process by which thrombi are dissolved

thrombolytic pertaining to a drug or other agent that dissolves thrombi

thrombolytic therapy (TT) use of drugs such as tissue plasminogen activator, urokinase, or streptokinase to dissolve an arterial clot.

thrombolytic any of several drugs that help dissolve clots, such as streptokinase, urokinase, and TPA (tissue plasminogen activator).

thrombophlebitis inflammation of a vein, often accompanied by formation of a clot

thrombosis an abnormal vascular condition in which thrombus develops within a blood vessel of the body thrombus an aggregation of platelets, fibrin, and cellular blood components that can cause obstruction of a blood vessel

thromboxane A2 (TxA2) a substance released from platelets after the platelets are activated following damage to the blood vessel walls. Thromboxane A2 promotes thrombus formation by stimulating platelet aggregation. Other substances released on platelet activation are adenosine diphosphate (ADP) and serotonin. Aspirin inhibits thromboxane A2 (TxA2) formation and its release from the platelets, thus partially impeding platelet aggregation.

thrombus formation the formation of a blood clot (coagulation) involving a complex interaction between certain blood components (i.e., platelets, prothrombin, and fibrinogen) and von Willebrand factor (vWF), collagen fibers, and tissue factor present in the endothelium and intima lining the blood vessel walls. The four phases of thrombus formation are as follows:

• Phase I: Platelet adhesion. See Platelet adhesion.

• Phase II: Platelet activation. See Platelet activation.

• Phase III: Platelet aggregation. See Platelet aggregation.

• Phase IV: Thrombus formation.

• Also refers to the fourth phase of thrombus formation when the fibrinogen between the platelets is converted into stronger strands of fibrin by the action of thrombin, itself converted from prothrombin by tissue factor. Plasminogen usually becomes attached to the fibrin during its formation. As the thrombus grows, red cells and leukocytes (white cells) become entrapped in the platelet-fibrin mesh.

thrombus (blood clot) an aggregation of platelets, fibrin, clotting agents, and red and white blood cells attached to a blood vessel wall.

thyroidectomy surgical removal of the thyroid gland

thyrotoxicosis a toxic condition caused by hyperactivity of the thyroid gland

tibial of or pertaining to the tibia

tidal volume (VT) the volume of air that is inhaled or exhaled from the lungs during effortless breath

time constant measure of the time required for the passive respiratory system to respond to abrupt changes in ventilatory pressure; expressed in units of time (usually seconds) and calculated as resistance times compliance.

timed walk test test focused on functional performance that generally involves having a patient walk over a measured course at a set duration of time (for example, 6 or 12 minutes). Patients are encouraged to go as far as they can, and supplemental oxygen is given as necessary.

timing flip-flop a fluidic control device that serves as an on/off switch.

tinnitus ringing in the ears

Tissot spirometer a water-sealed spirometer with a volume of approximately 100 liters. It was designed for collecting and measuring large volumes of exhaled air.

tissue factor a substance present in tissue, platelets, and leukocytes that when released after injury, initiates the conversion of prothrombin to thrombin.

tissue plasminogen activator (tPA) a clot-dissolving enzyme normally present in the endothelium of the blood vessel wall that activates plasminogen to convert to plasmin, which, in turn, dissolves the fibrin (fibrinolysis), causing the thrombus to break apart (thrombolysis).

tissue resistance to ventilation the work or pressure required to displace involved body tissues during ventilation.

TNK-tPA tenecteplase (TNK-tPA), a thrombolytic agent.

TNKase trade name for tenecteplase (TNK-tPA), a thrombolytic agent.

tolerance drug property in which the dose required to achieve the same effect increases gradually over time.

tomography an x-ray technique that produces a film representing a detailed cross-section of tissue structure at a predetermined depth

Tone-Tzanck test

tone that state of a body or any of its organs or parts in which the functions are healthy and normal.

tonicity an expression of the amount solute in a solution.

tonometry measurement of exact gas tensions in whole, fresh blood; because of the unique O2-binding characteristics of hemoglobin and complex viscosity characteristics of normal fresh blood, whole blood must be carefully tonometered so that exact gas tensions can be prepared for analysis by a blood gas instrument.

torr a unit of pressure equivalent to 1/760 atmosphere at STPD; 1 mm Hg

Torsade de pointes a form of ventricular tachycardia characterized by QRS complexes that gradually change back and forth from one shape and direction to another over a series of beats. A French expression meaning "twisting around a point."

tort a legal wrong committed upon a person or property independent of contract

tortfeasor a wrong doer; the individual who commits or is guilty of a tort

total anomalous pulmonary venous return rare congenital cardiac defect in which the pulmonary veins attach directly to the right atrium or to various veins draining into the right atrium rather than directing flow to the left atrium. Clinical manifestations include cyanosis, pulmonary congestion, and heart failure.

total buffer base (BB) the total quantity of all blood buffers capable of binding hydrogen ions, normally ranges from 48 to 52 mEq/L

total lung capacity (TLC) the total amount of gas in the lungs after a maximum inspiration  

total parenteral nutrition (TPN) administration of a nutritionally adequate hypertonic solution that can meet the needs of a patient who cannot eat by mouth.

total volume output in ventilators the sum of nebulizer gas volume and ventilatory gas volume.

tourniquet a device applied around an extremity that is designed to compress blood vessels and thereby prevent blood flow to or from the distal area

toxoplasmosis a disease caused by infection with protozoa found in many mammals and birds

tPA tissue plasminogen activator (tPA). See Alteplase (t-PA).

TP segment the section of the ECG between the end of the T wave and the onset of the P wave. Used as the baseline reference for the measurement of the amplitude of the ECG waves and complexes.

trachea the large main intrathoracic airway

tracheal button a device used to provide a temporary seal in a tracheostomy; used for weaning a patient from the artificial airway.

tracheal gas insufflation injection of fresh gas into the central airways for the purpose of improving the efficiency of alveolar ventilation and/or minimizing the ventilatory requirement.

tracheitis any inflammatory condition of the trachea

tracheobronchial of or pertaining to the trachea and large bronchi  

tracheobronchial stent bronchoscopically placed slender rod or threadlike device used as an airway support and indicated as a temporizing or palliative measure in a variety of patients.

tracheobronchomegaly a rare congenital condition in which the size of the large airways are greatly enlarged

tracheoesophageal of or pertaining to the trachea and esophagus, as with a tracheoesophageal fistula

tracheomalacia softening of the tracheal cartilages

tracheostomy an opening through the neck into the trachea, through which an indwelling tube may be inserted tracheotomy the procedure by which an incision is made into the trachea through the neck below the larynx, in order to gain access to the lower airways

tracheostomy tube hollow, curved tube of metal, rubber, or plastic that is surgically inserted in the trachea to relieve a breathing obstruction.

transairway pressure the barometric pressure difference between the mouth pressure and the alveolar pressure.

transbronchial across the bronchi or bronchial wall, as a trans bronchial biopsy

trans bronchial biopsy primary bronchoscopic technique for evaluating the alveolar compartment, particularly useful for sampling peripheral parenchymal masses, diagnosing a select number of specific interstitial lung diseases, and obtaining tissue specimens for culture or documentation of tissue invasion/microorganism pathogenicity.

transbronchial needle aspiration (TBNA) innovative bronchoscopic diagnostic technique used for staging mediastinal lymph nodes in suspected bronchogenic lung cancer, diagnosing submucosally infiltrating or extrinsically compressing tumors, approaching endobronchial tumors with necrotic or friable outer layers, and increasingly, diagnosing peripheral nodules.

transcutaneous across the skin, as a transcutaneous P02 electrode

transcutaneous electrical nerve stimulation (TENS) electrical stimulation of nerves for relief of pain

transcutaneous electrode a monitoring electrode that measures or indicates changes in physiologic conditions across the skin.

transcutaneous monitor means of respiratory monitoring of blood gases through electrodes applied to the skin.

transcutaneous overdrive pacing the use of a transcutaneous pacemaker to terminate certain arrhythmias such as polymorphic ventricular tachycardia with a prolonged QT interval (with pulse) and torsade de pointes (with pulse). This is done by adjusting the pacemaker's rate to one that is greater than that of the arrhythmia.

transcutaneous pacing (TCP, TC pacing) the delivery of electrical impulses through the skin to treat bradycardias from whatever cause, ventricular asystole, and pulseless electrical activity using an external artificial pacemaker. External cardiac pacing.

trans diaphragmatic pressure (Pdi) specific measure of diaphragm strength; made by measuring esophageal (Pes) and gastric (Pga.) pressures via balloon-tipped catheters placed in the midesophagus and in the stomach, respectively. Pdi is then calculated as the algebraic subtraction of Pes from Pga [Pdi = Pga - Pes)].

transducer type of passive or active sensor that converts one form of energy directly into another, particularly, but not exclusively, in most medical applications, converting mechanical into electrical energy, such as with pressure or ultrasound transducers.

transect to sever or cut across, as in preparing a cross­section of tissue

trans esophageal echocardiography (TEE) diagnostic test in which a small ultrasound transducer is passed posterior to the heart via the esophagus, allowing close investigation of valvular heart disease because of the proximity of the transesophageal probe to the heart and the absence of intervening anatomic barriers such as the thoracic ribs; includes all aspects of transthoracic imaging, including two-dimensional, Doppler, and color Doppler techniques.

transferrin globulin in blood serum that transports iron

transfusion the direct introduction of blood or blood products from another source into the blood stream

transient passing especially quickly into and out of existence; passing through or by a place with only a brief stay.

transmural extending from the endocardium to the epicardium.

transmural across the wall; usually pertains to the pressure difference between inside and outside a vessel or conducting tube

transmural, Q wave MI an infarction in which the zone of infarction involves the entire full thickness of the ventricular wall, from the endocardium to the epicardial surface. Abnormal Q waves are usually present.

transplacental across or through the placenta, specifically in reference to the exchange of nutrients, waste products, and other material between the developing fetus and the mother

transpulmonary across the lung; of or pertaining to the difference in a parameter (such as pressure) between the alveoli and pleural space

transpulmonary pressure the difference between the alveolar pressure and the pleural pressure.

transrespiratory across the respiratory system; of or pertaining to the difference in a parameter (such as pressure) between the alveoli and the body surface

transrespiratory pressure gradient the pressure differential between the mouth and the alveoli that causes gas to flow in and out of the lungs

transthoracic across the thorax; of or pertaining to the difference in a parameter (such as pressure) between the pleural space and body surface

transthoracic needle aspiration (TNA) sensitive, specific tissue sampling and testing used in the diagnosis of pneumonia, especially anaerobic. However, TNA and TTA are rarely performed in clinical practice.

transthoracic pressure the difference between the alveolar pressure and the body surface pressure.

transtracheal aspiration (TTA) technique for collecting sputum that was designed to bypass the upper airway, with its potential contaminants, by inserting a sterile needle directly into the trachea through the cricothyroid membrane and aspirating tracheal secretions.

transtracheal catheter small-diameter Teflon catheter that is surgically inserted into the trachea between the second and third tracheal rings, connected to a small flange, and held in place by an adjustable chain. Oxygen supply tubing connects directly to the catheter and delivers oxygen into the mid trachea.

transudate a fluid passed through a membrane or squeezed through a tissue or into the space between the cells of a tissue

transudative pleural effusion a pleural effusion low in protein and LDH, usually caused by congestive heart failure, nephrosis, or cirrhosis

traumatic brain injury a general term referring to any class of either focal or diffuse lesions that can result from head trauma. These lesions can include injury to the nerve body (axon), hypoxic brain damage, swelling, hemorrhage, contusions, laceration, or infection

treatment regimen a comprehensive plan of various treatments designed to combat a certain disease or disorder

trendelenburg position one in which the patient is supine on the backboard, the head of which is tilted downward 30 to 40 degrees, and the patient's knees are bent.

trepopnea labored breathing in the upright position

triage a classification of casualties of war and other disasters according to the gravity of injuries, urgency of treatment, and place for treatment

triaxial reference figure a guide for determining the direction of the Q RS axis in the frontal plane, formed by the lead axes of the three limb leads or the three augmented leads, spaced 60° apart around a zero reference point. The two triaxial reference figures, one formed by the standard limb leads and the other by the augmented leads, superimposed, form the hexaxial reference figure.

tricuspid valve a valve with three main cusps situated between the right atrium and right ventricle of the heart. The tricuspid valve includes the ventral, dorsal, and medial cusps. The cusps are composed of strong fibrous tissue and are anchored to the papillary muscles of the right ventricle by several tendons. As the right and left ventricles relax during the diastolic phase of the heartbeat, the tricuspid valve opens, allowing blood to flow into the ventricle. In the systolic phase of the heartbeat, both blood-filled ventricles contract, pumping out their contents, while the tricuspid and mitral valves close to prevent any backflow.

trigeminy a series of groups of three beats, usually consisting of two normally conducted QRS complexes followed by a premature contraction. The premature contraction may be atrial, junctional, or ventricular in origin (i.e., atrial trigeminy, junctional trigeminy, ventricular trigeminy).

trigger any variable used for initiation of the inspiratory phase (that is, pressure, volume, flow, or time).

triggered activity see Afterdepolarization.

trigger level control the device that sets the inspiratory force needed to begin a mechanical inspiration.

trigger sensitivity the amount of negative pressure (inspiratory effort) needed to cycle a ventilator into the inspiratory mode.

triglyceride most abundant lipid, which functions as the body's most concentrated source of energy; its basic building blocks are a glycerol molecule and three fatty acids.

trimester one of the three periods of approximately three months into which pregnancy is divided.

triple point that combination of temperature and pressure that allows the solid, liquid, and vapor forms of a given substance to exist in equilibrium with one another

triple-stage reducing valve a pressure reducing system that reduces pressure from 2200 to 750 to 50 psig.

triplicate method a method used to determine the heart rate.

TTOT abbreviation for transtracheal oxygen therapy

tube thoracoscopy placement of a thoracostomy tube (chest tube) into the pleural space to evacuate air or blood in the presence of pneumothorax or hemothorax.

tuberculosis a chronic granulomatous infection caused by an acid-fast bacillus, Mycobacterium tuberculosis. It is generally transmitted by the inhalation or ingestion of infected droplets and usually affects the lungs, although infection of multiple organ systems occurs

tumor suppressor genes genetic unit that is able to reverse the effect of a specific kind of mutation in certain tumors.

turbinates bony structures that extend from the lateral walls of the interior nasal passages

turbulent flow mixture of fluid velocities in which friction has a particularly prominent effect (as opposed to laminar flow) and which varies directly with square of flow rate, and carries a term for friction, implying greater resistance at equivalent flows.

turgor normal tension in a cell that results in normal strength and tension of the skin

T wave the part of the ECG representing repolarization of the ventricles that follows the QRS complex from which it is separated by the ST segment if it is present. It may be positive (symmetrically tall and peaked) or negative (deeply inverted).

tympanic membrane eardrum

tympany loud, drumlike, high-pitched sound typically heard over a gastric bubble during percussion examination.

Type I cells alveolar epithelial cells that form part of the alveolar-capillary complex and cover a large portion (90%) of the alveolar surface, facilitating the movement of gases across this surface.

Type II cells alveolar cells that produce surfactant and surfactant-associated proteins.

typical pneumonia any of several pneumonias usually caused by pneumococcus, but also by H. influenzae, Enterobacteriaceae, and S. aureus; characterized by abrupt onset of chills, high fever, pleuritic chest pain, and cough productive of rusty or purulent sputum; physical signs of consolidation such as bronchial breath sounds and inspiratory crackles are present; lobar or segmental consolidation is seen on the chest radiograph, and leukocytosis is present.

Tzanck test diagnostic test that examines the tissue of a lesion to determine the type of cell present