W

wandering atrial pacemaker (WAP) an arrhythmia originating in pacemakers that shift back and forth between the SA node and an ectopic pacemaker in the atria or AV junction. It is characterized by P waves varying in size, shape, and direction in any given lead.

warning arrhythmias PVC's that are more prone than others to initiate life-threatening arrhythmias, particularly after an acute myocardial infarction or ischemic episode:

• PVC's falling on the T wave (the R-on-T phenomenon)

• Multiform and multifocal PVC's

• Frequent PVC's of more than five or six per minute

• Ventricular group beats with bursts or salvos of two, three, or more

water-weighted diaphragm a PEEP device in which a water column placed in contact with the diaphragm of an expiration valve creates a PEEP pressure equal to the height of the water column.

watt a unit of power, equivalent to work done at the rate of 1 joule per second

watt/seconds units of electrical energy delivered by a source of energy, such as a defibrillator. One watt/second equals 1 joule.

waves refers to various components of the ECG-the P, Q, R, S, T, and U waves. Waves may be large or small.

weaning removing a patient gradually from dependency on mechanical ventilation while maintaining an appropriate balance between the load placed on the respiratory muscles and the ability of the muscles to meet that load.

wedge pressure see pulmonary artery wedge pressure (PAWP).

wellness programs programs aimed at keeping people healthy through classes that educate consumers so that they can maintain, and possibly even improve their quality of life, covering such topics as the benefits of diet, good sleep habits, relaxation techniques, routine exercise, diagnostic screenings, and the psychosocial aspects of health, with an emphasis on preventing disease and establishing and maintaining healthy habits for life.

Wenckebach block see Second-degree AV block type I AV block (Wenckebach)  

Wenckebach phenomenon named for Karel F. Wenckebach, Dutch-Austrian physician (1864-1940), a form of second-degree atrioventricular block with a progressive beat-to-beat prolongation of the PR interval, finally resulting in a nonconducting P wave. At this point the sequence recurs and is referred to as Wenckebach periodicity. Also called Mobitz I and Type I AV block.

western blot test a test to identify and analyze protein antigens

wheal a smooth, round elevated area of the skin with red edges and a white center, which is usually accompanied by itching; hives

Wheatstone bridge circuit used to measure electrical resistance changes in strain gauges built into pressure transducers; solid-state bridge circuits have replaced the classic galvanometer and resistor array.

wheezes form of rhonchus characterized by either high- or low-pitched musical quality, caused by high-velocity air flow through a narrowed airway.

whispered pectoriloquy voice sound heard during auscultation of the lungs, typically heard with lung consolidation.

wick humidifier a type of humidification system in which the gas flow is exposed to a water-saturated cloth, paper, or polyethylene membrane.

wide-QRS-complex tachycardia a tachycardia with abnor­mally wide QRS complexes (0.12 second or greater) that may be ventricular tachycardia or a supraventricular tachycardia with wide QRS complexes resulting from a preexisting bundle branch block, aberrant ventricular conduction, or ventricular preexcitation.

"Window" theory refers to the popular theory of why Q waves occur over infarcted myocardium. According to this theory, the facing leads over electrically inert infarcted myocardium (or "window") view the endocardium of the opposite noninfarcted ventricular wall, and detect the R waves generated by the opposite wall as large Q waves.

work of breathing pressure needed to move a volume of gas into the lungs.

workload the work output being performed by a group of muscles per minute of work. Units of watts or kilopond-meters (KPM) are used to measure workload.

X

xanthine a nitrogenous byproduct of the metabolism of nucleoproteins

xenon a chemically unreactive gaseous element with an atomic weight of 131.30; symbol Xe.

xerostomia dry mouth; reduced amount of saliva

xiphisternal of or pertaining to junction of the xiphoid process with the body of the sternum

xiphoid of or pertaining to the xiphoid process of the sternum

xiphoid process the pointed lower portion of the sternum

Y

yeast Single-cell, nucleated fungus that reproduces by budding

Z

ZEEP abbreviation for zero end-expiratory pressure

"Zero" center of the heart refers to the hypothetical reference point with an electrical potential of zero, located in the electrical center of the heart-left of the interventricular septum and below the AV junction. Formed by connecting the extremity electrodes together, the "indifferent," zero reference point is used as the central terminal for the unipolar leads. It also represents the central point for the hexaxial reference figure.

zero end-expiratory pressure (ZEEP) the default baseline value during positive pressure ventilation; it is normally in effect unless purposely changed

Ziehl-Neelsen test one of the most widely used methods of acid-fast staining, commonly used in the microscopic examination of a smear of sputum suspected of containing Mycobacterium tuberculosis

zones of infarction (necrosis), injury, and ischemia a myocardial infarction at its height typically consists of a central area of dead, necrotic tissue-the zone of infarction (or necrosis), surrounded immediately by a layer of injured myocardial tissue-the zone of injury, and, lastly, by an outer layer of ischemic tissue-the zone of ischemia.

zone valve a valve that controls the flow of gas to specific areas served by a bulk gas system.