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W-X-Y-Z
L
abbreviation for liter.
lactate
anion of lactic acid most commonly formed in ischemic cells as a
consequence of anaerobic glycolysis and the use of pyruvate for
generation of ATP; frequently used as an indicator of the
severity of shock and to give a rough idea of tissue perfusion,
oxygen delivery, and oxygen utilization.
lactic acid
acid formed in muscles during activity by the breakdown of sugar
without oxygen.
LAD
left anterior descending coronary artery. See Coronary
circulation.
Lambert-Eaton syndrome a disorder of neuromuscular
conduction commonly associated with an underlying malignancy
that leads to muscle weakness often with sensory deficits that
can often be improved by repetitive muscle contraction against
pressure
laminar
flow a pattern of flow consisting of concentric
layers of fluid flowing parallel to the tube wall at linear
velocities that increase toward the center; considered smooth,
uninterrupted flow.
lancet
a small, pointed, two-edged surgical knife.
laparoscopy
a surgical procedure to examine the abdomen using an endoscope
called a laparoscope
LaPlace
formula a principle of physics that the tension on
the wall of a sphere is the product of the pressure times the
radius of the chamber
large
squares the areas on ECG paper enclosed by the dark
horizontal and vertical lines of the grid.
large
volume nebulizer an aerosol-producing device designed
to deliver enough humidified inspired gases to provide adequate
flow to meet patient inspiratory flow rates.
laryngeal
mask airway (LMA) device for both routine management
of the airway during general anesthesia and as an emergency
airway adjunct in the difficult airway.
laryngectomy a surgical removal of the larynx,
performed to treat cancer of the larynx laryngitis inflammation
of the larynx
laryngoscope an endoscope for examining the larynx
laryngoscopy visual examination of the larynx using a
laryngoscope
laryngospasm an involuntary contraction of the
laryngeal muscles resulting in complete or partial closure of
the glottis
laryngotracheobronchitis an inflammation of the
larynx, trachea, and large bronchi that can result in
hoarseness, a nonproductive cough, and dyspnea. Also referred to
as croup.
laryngotracheitis inflammation of the larynx and
trachea
larynx
musculocartilaginous structure behind the tongue and hyoid bone
that acts as a sphincter to protect the entrance to the trachea;
functions secondarily as the "voice box."
laser
bronchoscopy use of rigid bronchoscopy with laser
technology to make use of a wider diameter of the working
channel, which allows for simultaneous visualization, laser use,
and suctioning; best applied to symptomatic centrally located,
unresectable, endobronchial malignancies; appropriately located
benign tumors without extrabronchial involvement (such as
papillomas); luminalobstructions such as webs or tracheal
granulomas; and non inflammatory tracheal stenoses.
latent heat
the amount of heat needed for a substance to change its state of
matter.
latent (or
subsidiary) pacemaker cells cells in the electrical
conduction system with the property of automaticity, located
below the SA node. These cells hold the property of automaticity
in reserve should the SA node fail to function properly or
electrical impulses fail to reach them for any reason, such as a
disruption in the electrical conduction system.
lateral
away from the body midline; situated on the side
lateral
decubitus a side-lying position (either left or
right)
lateral
leads leads V5 and V6 the left precordial leads.
lateral MI
a myocardial infarction commonly caused by occlusion
of the laterally located diagonal arteries of the left anterior
descending (LAD) coronary artery and/or the anterolateral
marginal artery of the left circumflex coronary artery.
lavage
the cleaning out of a cavity with liquid
law of
continuity the velocity of a fluid moving through a
tube and constant flow varies inversely with the available
cross-sectional area
LBB
see Left bundle branch (LBB).
LBBB
see Left bundle branch block (LBBB).
lead
a lead of the ECG. See ECG lead.
lead axis
see Axis of a lead (lead axis).
lead I,
monitoring lead see Monitoring lead I.
lead II,
monitoring lead see Monitoring lead II.
lead III,
monitoring lead see Monitoring lead III.
lead MCL1
monitoring lead see Monitoring lead MCL1
lead MCL6,
monitoring lead see Monitoring lead MCL6.
leaf value
a thin membrane that overlays an orifice and that when closed
prevents fluid (gas or liquid) transmission through the opening.
left
anterior fascicular block (LAFB) absent conduction of
electrical impulses through the left anterior fascicle of the
left bundle branch. Also referred to as left anterior
herniblock.
left atrial
enlargement (left atrial dilatation and hypertrophy)
usually caused by increased pressure and/or volume in the left
atrium. It is found in mitral valve stenosis and insufficiency,
acute myocardial infarction, left heart failure, and left
ventricular hypertrophy from various causes, such as aortic
stenosis or insufficiency, systemic hypertension, and
hypertrophic cardiomyopathy.
left axis
deviation (LAD) a QRS axis greater than -30° (-30° to
-90°).
left bundle
branch block (LBBB) defective conduction of
electrical impulses through the left bundle branch. Left bundle
branch block may be complete or incomplete and be present with
or without an intact interventricular septum.
left bundle
branch (LBB) part of the electrical conduction system
of the heart that conducts electrical impulses into the left
ventricle. It consists of the left common bundle branch (or main
stem), which divides into two bundles of fibers, the left
anterior fascicle (LAF) and the left posterior fascicle (LPF).
left
posterior fascicular block (LPFB) absent conduction
of electrical impulses through the left posterior fascicle of
the left bundle branch. Also referred to as left posterior
herniblock.
left
precordial (or lateral) leads leads V5 and V6.
left
ventricular failure inadequacy of the left ventricle
to maintain normal circulation of blood. This results in
pulmonary congestion and edema.
left
ventricular hypertrophy (LVH) increase in the
thickness of the left ventricular wall because of chronic
increase in pressure and/or volume within the ventricle. Common
causes include mitral insufficiency, aortic stenosis or
insufficiency, and systemic hypertension.
Lenegre's
disease/Lev's disease idiopathic degenerative disease
of the electrical conduction system with fibrosis and/or
sclerosis and disruption of the conduction fibers. A cause of
bundle branch and fascicular blocks.
length of
stay (LOS) a measure pertaining to the number of
elapsed days between a patient's admission and their discharge
from an inpatient healthcare facility
lesion
a general term referring to any injury or pathological change in
body tissue
leukocyte
white blood cell.
leukocytopenia an abnormal decrease in white blood
cells
leukocytosis elevated white cell count; often a sign
of significant infection but also can be associated with
elevated glucocorticoids (for example, stress reaction, steroid
administration) and in a number of hematologic malignancies.
leukopenia
decreased white cell count; often indicates overwhelming
infection.
leukotriene
anyone of several compounds that can act on smooth muscle cells
through its own receptor to produce tonic bronchoconstriction.
LFPPV-ECC02R acronym for low-frequency positive
pressure ventilation with extracorporeal carbon dioxide removal;
a mode of ventilatory support designed to minimize the harmful
effects of conventional mechanical ventilation
LGA
abbreviation for large for gestational age; pertaining to
newborn infants whose body weight falls above the 90th
percentile for their gestational age
liability
a legal obligation or responsibility
libel
a false accusation written, printed, or typewritten, or
presented in a picture or a sign that is made with malicious
intent to defame the reputation of a person who is living or the
memory of a person who is dead, resulting in public
embarrassment, contempt, ridicule, or hatred
lidocaine
an antiarrhythmic used to treat premature ventricular
contractions (PVC's) and monomorphic and polymorphic ventricular
tachycardia with a pulse.
life-threatening arrhythmias include ventricular
fibrillation, pulseless ventricular tachycardia, ventricular
asystole, and pulseless electrical activity.
ligamentum
nuchae upward continuation of the supraspinous
ligament, extending from the 7th cervical vertebra to the
occipital bone.
limb-girdle
muscular dystrophy heterogenous group of muscle
dystrophies characterized primarily by weakness of the shoulder
and pelvic girdles with sparing of the facial muscles.
limb or
extremity leads the three standard (bipolar) limb
leads (leads I, II, and III) and the three augmented (unipolar)
leads (leads aVR, aVL, and aVF).
limit
variable ventilation variable that rises no higher
than a given preset value or increases to a preset value before
inspiration ends.
linea alba
"white line" of connective tissue in the middle of the abdomen
from sternum to pubis.
linear-drive piston a piston whose movement is
governed by a straight line (linear) movement of a shaft that is
connected to the piston head.
linear
measurements where measured values are equal to
actual values when compared over a range of measurements.
linear
response a response or output that is directly
proportional to the input.
lingual
aerosol pertains to a method of delivering a drug by
spraying it under the tongue.
lingula
the lower division of the left upper lobe that corresponds
developmentally to the right middle lobe
lipase
a fat-splitting enzyme produced by the pancreas
lipid
organic biomolecule that is soluble in nonpolar organic
solvents, such as ether, alcohol, or benzene but is not soluble
in water; composed primarily, but not exclusively, of carbon,
hydrogen, and oxygen.
liter (L)
a metric measurement of volume. One liter is equal to 1000
milliliters (ml), or 1.1 quarts.
lithotripsy
crushing of stones (e.g., kidney stones and gallstones)
liver
enzymes enzymes that are present in the liver and may
indicate liver function, and dysfunction elsewhere (for example,
alanine aminotransferase [ALT] is present in liver cells, and an
increased serum level is an indicator of liver cell injury;
aspartate aminotransferase [AST] is present in liver cells but
is also present in cardiac, skeletal, kidney, and brain tissue;
mildly elevated AST levels suggest alcoholic liver injury;
elevation of liver ALP is indicative of intrahepatic or
collecting system bile drainage abnormalities [cholestasis]; and
elevated gamma-glutamyltransferase serum levels also indicate
cholestasis).
LMW
heparin low-molecular-weight (LMW) heparin, an anticoagulant.
loading
dose a single large dose of a drug that produces an
initial high therapeutic blood level necessary to treat certain
conditions.
lobar
pertaining to a lobe, such as the lobes of the lung.
lobectomy
a type of chest surgery in which a lobe of a lung is excised,
performed to remove a malignant tumor and to treat uncontrolled
bronchiectasis, trauma with hemorrhage, or intractable
tuberculosis
lobes
upper, middle, and lower major divisions within each lung;
further subdivided into bronchopulmonary segments that
correspond to the distribution of a specific bronchus.
lobule
literally a small lobe; in pulmonary anatomy may refer to the
primary lobule or terminal respiratory unit of the lung (also
called the acinus), or the secondary lobule; the secondary
lobule is the smallest gross anatomical unit of lung tissue set
apart by true connective tissue septa and corresponds to
clusters of from three to five primary lobules
lock-out
cartridge a control that inhibits (locks out) the
functions of other controls or systems.
locus of
control attitude towards responsibility for one's
behavior. Persons with an internal locus of control believe they
can control their own destiny; those with an external locus of
control tend to believe that their lives are controlled by
forces outside themselves.
logarithm
extension of the use of scientific notation, originally invented
to ease the difficulties of manual calculations of large or
small numbers, in which logs (base 10) are the replacement of a
whole number and an appropriate fraction for the real number
(that is, log 10 = 1, log 15 = 1.176, log 150 = 2.176). The
whole number position refers to the power of 10, and the
decimals to the right refer to the actual numeric value.
long-term
oxygen therapy (LTOT) only pharmacologic intervention
available for hypoxemic patients with COPD that has been shown
to prolong survival.
lordosis
backward curvature of the spine.
lordotic
pertaining to a radiographic position in which the patient
stands with his or her back toward the film and leans backward,
such that only the shoulders, neck, and head touch the film;
this positions the x-ray beam at an angle ideal for viewing the
lung apices without obstruction by the normally superimposed
shadows of the clavicles
Lovenox
trade name for enoxaparin, a low-molecular-weight (LMW) heparin
used as an anticoagulant. See Anticoagulant.
low battery
alarm a warning that the power (charge) remaining in
a battery is below acceptable limits.
lower case
letters lower case letters, such as q, r, s, are used
to designate small deflections of the ECG.
low-flow
system a variable performance oxygen therapy device
that delivers oxygen at a flow that provides only a portion of
the patient's inspired gas needs. Also called variable
performance system
lower
respiratory tract infection any infectious disease of
the left and right bronchi and the alveoli
low inlet
gas alarm a warning that system pressure is below
optimal pressure standards.
low-molecular-weight (LMW) heparin an anticoagulant.
low-pressure reducing valve a pressure-regulating
system designed to operate below 50 psig.
low-pressure regulator a low-pressure reducing valve
combined with a flowmeter.
low-residual-volume, high-pressure cuff a type of
endotracheal or tracheostomy tube seal that requires low volumes
at high pressures to achieve an airtight seal.
low-resistance/high-compliance system A system where the forces
resisting flow are low and the volume change per unit of
pressure exerted is high.
Lund-Browder
chart tool used to evaluate the extent of cutaneous
wounds and their potential influence on pulmonary function in
patients with burn injuries.
lumbar
puncture a surgical procedure to withdraw spinal
fluid for analysis or the injection of an anesthetic solution
lumen
inner open space of a tubular organ, such as a blood vessel or
intestine.
lumpectomy
removal of just the tumor from the breast
lung
abscess an inflammatory lesion resulting in necrosis
of lung tissue and associated with one or more of the following:
suppression of the cough reflex, aspiration of infected
material, bronchial obstruction, pneumonias, ischemia, as with
pulmonary infarction; or blood sepsis
lung cancer
a pulmonary malignancy attributable in the majority of cases to
cigarette smoking. Epidermoid cancers and adenocarcinomas each
account for approximately 30% of lung tumors, about 25% are
small or oat-cell carcinomas, and 15% are large-cell anaplastic
cancers
lung
compliance the change in lung volume per unit
pressure change.
lung
protective ventilation strategy ventilatory technique
in which the plateau pressure is kept below 35 cm H20, PEEP is
applied to maintain alveolar recruitment, and FIO2 is kept below
0.60.
lung
transplantation transfer of a pulmonary organ system
from a donor to a recipient; recognized as an accepted therapy
for end-stage CF lung disease.
lung volume
reduction surgery procedure that removes 20% to 30%
of the lung tissue most severely affected by emphysema,
encouraging the remaining lung to gain recoil elasticity and
improve lung, chest wall, and diaphragmatic mechanics in
addition to right ventricular performance.
lupus
erythematosus a chronic, superficial inflammation of
the skin in which reddish lesions or macules up to 3 to 4 cm in
size spread over the body
LVEDP
abbreviation for left ventricular end-diastolic pressure
lymph
a mostly clear, colorless, transparent, alkaline fluid found
within the lymphatic vessels; formed in tissues throughout the
body
lymphadenitis inflammation of the lymph nodes
lymphadenopathy disease of the lymph nodes
lymphocyte
small agranulocytic leukocytes originating from fetal stem cells
and developing in the bone marrow. Lymphocytes normally comprise
25% of the total white blood cell count but increase in number
in response to infection. Two forms occur: B cells and T cells.
B cells circulate in an immature form and synthesize antibodies
for insertion into their own cytoplasmic membranes. T cells are
lymphocytes that have circulated through the thymus gland and
have differentiated to become thymocytes. When exposed to an
antigen they divide rapidly and produce large numbers of new T
cells sensitized to that antigen.
lymphocytosis an excessive number of lymph cells
lyse
to break up, to disintegrate (e.g., to lyse a thrombus).
lysis
the process of breaking up or disintegrating (e.g., thrombolysis).
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