Vacuum-Ventricular Diastole

vacuum an absence of pressure

vagal maneuvers methods to increase the vagal (parasympathetic) tone to convert paroxysmal supraventricular tachycardia. See Valsalva maneuver.

vagal (parasympathetic) tone see Parasympathetic (vagal) tone.

vagolytic of or pertaining to an action or agent that antagonizes or blocks parasympathetic activity

vagotomy a cutting of certain branches of the vagus nerve, performed with gastric surgery, to reduce the amount of gastric acid secreted and lessen the chance of recurrence of gastric ulcer

vagovagal reflexes reflexes caused by stimulation of parasympathetic receptors in the airways that can result in laryngospasm, bronchoconstriction, hyperpnea, and bradycardia; often associated with mechanical stimulation, as during procedures such as tracheobronchial aspiration, intubation, or bronchoscopy

vagus the 10th cranial nerve. It is a mixed nerve, having motor and sensory functions and a wider distribution than any of the other cranial nerves.

valance electron the number of electrons in the outer shell of an atom.

validity the degree to which the results of a given test actually reveal what the test intends to measure

valsalva maneuver forceful act of expiration with the mouth and nose closed, producing a bearing down on the abdomen. Used to increase the parasympathetic tone to convert paroxysmal supraventricular tachycardia.  

valvular heart disease any valvular lesion or abnormality that can be differentiated hemodynamically into two types, though a combination of both may exist: stenotic lesions due to a decreased valve orifice size/impaired valve opening or regurgitant lesions due to impairment of valve closure.

valvular regurgitation condition in which a proportion of the ventricular stroke volume moves retrograde through the value.

valvular stenosis narrowing of a heart valve.

Van der Waals forces the mutual attractive forces exerted between atoms or molecules in proximity to each other vaporization the process whereby matter in its liquid form is changed into its vapor or gaseous form

vapor a transition state between a liquid and a gas during which, through application of pressure/temperature changes, the transition may be reversed.

vaporizer a device that converts a liquid into a vapor; more specifically, an apparatus designed to increase ambient humidity using the principles of either evaporation or boiling

vapor pressure a colligative property of a solution that depends on the number of solute particles dissolved and not on chemical properties; for example, a solute added to a solvent dilutes it, displacing solution surface solvent particles and allowing fewer solvent particles to escape in the form of gas, thereby reducing the vapor pressure.

VAPS abbreviation for variable assist pressure support, a form of pressure support ventilation that assures a minimum tidal volume

variable AV block refers to an AV block with varying AV conduction ratios (i.e., the ratio of P, p', F, or f waves to QRS complexes varies).

variable performance device an oxygen therapy device that delivers oxygen at a flow that provides only a portion of the patient's inspired gas needs. Also called low flow system

variable restrictor a device that reduces flow incorporating an adjustable orifice.

vascular relating to or containing blood vessels.

vascular resistance value used to follow relative changes in afterload after cardiac interventions; calculated as

                           SVR = [(MAP - CVP)/CO] X 80.

vascular system the circulatory network composed of two major subdivisions: the systemic system and the pulmonary system.

vascularization the process by which body tissue becomes vascular and develops proliferating capillaries

vasculitis a narrowing of the lumen of any blood vessel, especially the arterioles and the veins in the blood reservoirs of the skin and the abdominal viscera

vasoconstriction narrowing the lumen of blood vessels.

vasoconstrictor a drug, hormone, or substance that constricts the lumen of blood vessels.

vasodilatation, vasodilation widening the lumen of blood vessels.

vasodilator a drug, hormone, or substance that dilates or widens the lumen of blood vessels.

vasomotor pertaining to the nerves and muscles that control the caliber of the lumen of the blood vessels vasopressin see ADH (antidiuretic hormone)

vasomotor tone the state of vascular contraction.

vasopressor agent used to increase blood pressure through a combination of vasoconstriction-causing higher flow resistance, therefore higher pressure and increased cardiac output.

vasovagal pertaining to a vascular and neurogenic cause.

VAT see Ventricular activation time (VAT).

VCV acronym for volume controlled ventilation, a mode of ventilatory support in which volume (or flow x time) serves as the cycle variable

vector a graphic presentation, using an arrow, of the electric current generated by the depolarization or repolarization of the atria and ventricles at anyone moment of time.

vectorborne transmission of infectious organisms from one host to another via an animal carrier, especially an insect

vein anyone of the many vessels that convey blood from the capillaries as part of the pulmonary venous system, the systemic venous network, and the portal venous complex. Most of the veins of the body are systemic veins that convey blood from the whole body (except the lungs) to the right atrium of the heart. Each vein is a macroscopic structure enclosed in three layers of different kinds of tissue homologous with the layers of the heart. The outer tunica adventitia of each vein is homologous with the epicardium, the tunica media with the myocardium, and the tunica intima with the endocardium. Deep veins course through the more internal parts of the body, and superficial veins lie near the surface, where many of them are visible through the skin. Veins have thinner coatings and are less elastic than arteries and collapse when cut. They also contain semilunar valves at various intervals to control the direction of the blood flow back to the heart.

velocity property of flow that determines diffusion and is inversely proportional to the square root of the molecular weight of a substance; equivalent to the kinetic energy of a fluid.

venostasis abnormally slow blood flow through the veins, often seen in distended veins. Also called phlebostasis.

venous pertaining to a vein or veins.

venous admixture the mixing of shunted, non-reoxygenated blood with reoxygenated blood distal to the alveoli.

venous return filling of the heart with blood from the venous circulation.

ventilation process by which gases are moved into and out of the lungs; in respiratory therapy, use of any of several devices that provide assisted respiration and intensive positive-pressure breathing.

ventilation/perfusion ratio measure of effective gas exchange in the lung, or V/Q ratio; this ratio should be 1 for the most effective gas exchange to occur.

ventilation-perfusion scan imaging technique used in the diagnosis of pulmonary embolism.

ventilator assisted individual (VAI) patient who requires the assistance of an artificial device for breathing.

ventilator a mechanical device that moves bulk gases into and out of the lungs.

ventilator associated pneumonia pneumonia in a mechanically ventilated patient developing after at least 48 hours of mechanical ventilation.

ventilator asynchrony a complication of mechanical ventilation in which the patient's spontaneous pattern of breathing is not synchronous with the pattern offered by the ventilator. This results in an increase in the work of breathing

ventilator induced lung injury damage to the lungs sustained during mechanical ventilation and caused by any of several factors, including alveolar overdistention and derecruitment resulting from high peak inflation volume (volutrauma), alveolar collapse (atelectrauma), or cyclical opening of an alveolus during inhalation and closure during exhalation, or by release of inflammatory mediators (cytokines, chemokines), which may trans locate into the pulmonary circulation, resulting in systemic inflammation.

ventilator inoperative alarm a system that warns of the non­functional status of a ventilator.

ventilatory cycle time the time it takes from the beginning of one inspiration to the beginning of the next inspiration.

ventilatory equivalent the relationship between minute ventilation and oxygen consumption or carbon dioxide production.

ventilatory failure a ventilatory disorder that results in a subject's PaC02 increasing to greater than or equal to 50 mm Hg.

ventilatory muscle training exercises designed to improve the strength and/or endurance of the muscles of breathing

ventilatory pattern the rate and volume characteristics of breathing over a period.

ventilatory period cycle time (or total cycle time); the reciprocal of ventilatory frequency.

ventilatory threshold (VT) during exercise, the point where increased levels of lactic acid result in an increased CO2 production and minute ventilation; the RQ equals or exceeds 1.0, indicating that CO2 production equals or exceeds O2 consumption; at this point metabolism becomes anaerobic, thereby decreasing energy production and increasing muscle fatigue

ventral pertaining to the anterior portion or front of the body.

ventricles small cavities making up two of the four chambers of the heart; the right side of the heart receives blood, and the right ventricle pumps it into the pulmonary arteries; blood returning from the pulmonary veins drain into the left atrium, into the left ventricle, and finally into the aorta, which dispenses it into the systemic circulation.

ventricular activation time (VAT) the time it takes for depolarization of the interventricular septum, the right ventricle, and most of the left ventricle, up to and including the endocardial to epicardial depolarization of the left ventricular wall under the facing lead. Also called the preintrinsicoid deflection or intrinsicoid deflection time (IDT).

ventricular arrhythmia an arrhythmia originating in an ectopic pacemaker in the ventricles. Also referred to as ventricular eetopy.

ventricular assist device (VAD) mechanical pump that can completely assume the workload of the right or left ventricle and restore normal hemodynamics; allows long-term support of circulation in patients with refractory heart failure and is used primarily as a bridge to transplantation.

ventricular asystole (cardiac standstill) cessation of ventricular contractions.

ventricular demand pacemaker (VVl) a pacemaker that senses spontaneously occurring QRS complexes and paces the ventricles when they do not appear.

ventricular diastole the interval or period during which the ventricles are relaxed and filling with blood. The period between ventricular contractions.

Ventricular Dilatation-vWF

ventricular dilatation distension of the ventricle because of increased pressure and/or volume within the ventricle; it may be acute or chronic.

ventricular enlargement includes ventricular dilatation and hypertrophy. Common causes include heart failure, pulmonary diseases, pulmonary or systemic hypertension, heart valve stenosis or insufficiency, congenital heart defects, and acute myocardial infarction. See Left ventricular hypertrophy (LVH), Right ventricular hypertrophy (RVH).

ventricular escape rhythm an arrhythmia arising in an escape pacemaker in the ventricles with a rate of less than 40 beats per minute.

ventricular fibrillation/pulseless ventricular tachycardia two life-threatening ventricular arrhythmias that result in cardiac arrest. Treatment is immediate defibrillation.

ventricular fibrillation (VF, V-FIB) an arrhythmia originating in multiple ectopic pacemakers in the ventricles characterized by numerous ventricular fibrillatory waves and no QRS complexes.

ventricular fibrillation (VF) waves bizarre, irregularly shaped, rounded or pointed, and markedly dissimilar waves originating in multiple ectopic pacemakers in the ventricles.

ventricular fusion beat see Fusion beat, ventricular.

ventricular hypertrophy enlargement of the ventricular myocardium, the result of an increase in the size of the muscle fibers because of chronic increase in pressure and/or volume within the ventricle. Common causes include heart failure, pulmonary diseases, pulmonary or systemic hypertension, heart valve stenosis or insufficiency, and congenital heart defects. See Left ventricular hypertrophy (LVH), Right ventricular hypertrophy (RVH).

ventricular overload refers to increased pressure and/or volume within the ventricles.

ventricular preexcitation the premature depolarization of the ventricles associated with an abnormal accessory conduction pathway, such as the accessory AV pathways or nodoventricular/fasciculoventricular fibers that bypass the AV junction or bundle of His, respectively, allowing the electrical impulses to initiate depolarization of the ventricles earlier than usual. This results in an abnormally wide QRS complex of greater than 0.10 second that characteristically has an abnormal slurring and sometimes notching at its onset-the delta wave. The PR interval is usually less than 0.12 second when ventricular preexcitation is the result of an accessory AV pathway and usually normal when nodoventricular/fasciculoventricular fibers are the cause. The term ventricular preexcitation is most commonly used to indicate ventricular preexcitation associated with accessory AV pathway conduction.  

ventricular repolarization the electrical process by which the depolarized ventricles return to their polarized, resting state. Ventricular depolarization is represented by the T wave on the ECG.

ventricular shift lateral movement of one of the ventricles of the brain to one side caused by pressure on the other side

ventricular "strain" pattern the changes in the QRS-ST-T complex produced by a downsloping ST segment depression and T wave inversion, characteristic of long-standing right or left ventricular hypertrophy. Also known as the "hockey stick" pattern.

ventricular systole the interval or period during which the ventricles are contracting and emptying of blood.

ventricular tachycardia (VT, V-TACH) an arrhythmia originating in an ectopic pacemaker in the ventricles with a rate between 100 and 250 beats per minute.

ventricular T wave (T wave) represents ventricular repolarization.

ventricular interdependence interaction between the left ventricle (LV) and the right ventricle (RV) both in systole and diastole through alterations in systemic and pulmonary venous return, LV and RV dimensional changes, and functional changes.

ventriculography radiographic examination of a ventricle of the heart after injection of a radiopaque contrast medium.

ventrolateral positioned or located toward the back and side

Venturi a device that incorporates a jet device to create pressure flow and admixture changes in a gas stream.

Venturi gate part of a mechanism in the Bird Mark series that balanced spring tension on a valve cover with driving pressure to adjust flow through a Venturi device.

Venturi meter mechanism designed by Giovanni Venturi to avoid generation of turbulent flow in a region of reduced diameter; ignoring any gravitational forces (minimal in low density gases and constant in a horizontal tube), the pressure gradient across a change of diameter will describe the velocity of flow.

Venturi PEEP valve a Venturi whose output pressure opposes gas flow through a one-way valve to increase end expiratory pressure.

Venturi principle physical rule stating that pressure drop across an obstruction can be restored provided that the angle of divergence is less than 15 degrees.

venule anyone of the small blood vessels that gather blood from the capillary plexuses and anastomose to form the veins.

veracity principle in which the health care practitioner tells the patient the truth.

vernier a control that has the ability to initiate small changes in a system; usually a dial that can be adjusted in small increments.

vertebra any of the 33 bones of the spinal column, composed of a body, a spinous process, and pairs of pedicles and processes between the vertebral column and sternum

vertex top of the head

vesicle a small blister-like elevation of the skin containing clear fluid

vesicular breath sounds low-pitched, low-intensity sounds heard over healthy lung issue.

vestibule a space or a cavity that serves as the entrance to a passageway, as the vestibule of the nose

vibration therapy maneuver used as part of conventional chest physiotherapy to assist patients in mobilizing secretions from the lower respiratory tract. Vibration is performed manually by pressing in the direction of the ribs and soft tissue of the chest during exhalation.

viral pneumonia uncommon but often severe pneumonia caused by any of the following viruses: influenza, parainfluenza, respiratory syncytial virus (RSV), cytomegalovirus (CMV), adenovirus, measles, varicella zoster, herpes simplex, Epstein-Barr, and hantavirus.

virtue ethics the viewpoint that asks what a virtuous person would do in a similar circumstance; it is based on personal attributes of character or virtue, rather than on rules or consequences

virulence the power of microorganisms to produce disease

visceral pleura a thin membrane covered by mesothelial cells that covers the entire surface of the lung, dipping into the lobar fissures

visceral pleural line white line in a radiographic image of the pneumothorax that represents the visceral pleura visualized between air in the pleural space laterally and air in the aerated lung medially and that establishes the radiographic diagnosis of pneumothorax.

viscosity force applied to interaction between adjacent fluid molecules; also, the internal friction of a fluid, which is independent of the density of that fluid.

viscous sticky; gummy; gelatinous.

viscus any organ enclosed within a cavity, such as the thorax or abdomen.

vital capacity (VC) the total amount of air that can be exhaled after a maximum inspiration; the sum of the inspiratory reserve volume, the tidal volume, and the expiratory reserve volume

V leads leads V1 V2, V3, V4, V5, and V6 See Precordial (unipolar) leads.

volatile acid an acid capable of chemically changing between the gaseous and liquid states. Carbon dioxide, with its ability to combined with water in the blood to form carbonic acid, is an example of a volatile acid.

voltage (amplitude) see Amplitude (voltage).

voltmeter a device containing a galvanometer that is designed for measuring the electrical potential in a circuit.

volume-controlled ventilation (VCV) mode of ventilation in which the ventilator controls the inspiratory flow and tidal volume is determined by the flow and the inspiratory time; in practice, the tidal volume in this mode is delivered regardless of resistance or compliance.

volume hold a ventilator control or a maneuver where a volume of gas is held in the patient's lungs for a period of time so static pressure can be read or gas distribution improved.

volume limit a setting that sets the maximum deliverable volume on a ventilator.

volume control a dial or setting that determines the volume to be delivered by a mechanical ventilator.

volume of distribution means used to convey drug distribution by calculating how much volume the drug would occupy if it were uniformly at its plasma concentration.

volumetric diffusive respiration pressure-controlled ventilation with a superimposed subtidal oscillation that facilitates clearance of endobronchial debris.

volume percent (Vol%) the number of milliliters (mL) of a substance contained in 100 mL of another substance.

volutrauma alveolar overdistension and damage due to ventilation with high peak inflation pressures  

von Willebrand factor (vWF) a protein stored in the endothelium of blood vessels, that when exposed to blood binds to the platelets' GP Ib and GP IIb/GP IIIa receptors, adhering the platelets to the collagen fibers in the blood vessel wall.

V/Q imbalance any abnormal deviation in the distribution of ventilation to perfusion among the lung's alveolar­capillary units

VQI abbreviation for ventilation-perfusion index, an estimate of the venous admixture or physiologic shunt occurring in the lungs

vortex shedding a characteristic of flow systems where pressure changes in flows that contact air foils are proportionate to the velocity of the gas, thus allowing for determination of pressure, flow, and volume.

VT/tl the mean spontaneous inspiratory flow, used to assess respiratory drive

vulnerable period of ventricular repolarization the part of the last phase of repolarization during which the ventricles can be stimulated to depolarize prematurely by a greater than normal electrical stimulus. This corresponds to the downslope of the T wave.

vWF see von Willebrand factor (vWF).