DEATH
D
death
Permanent cessation of all vital func-
tions. The classic indicators of death are
the permanent cessation of heart and
lung function, and, in almost all cases,
these
remain the
criteria by w hich
death is certified.
Brain death
is the
irreversible cessation of all functions
of the entire brain, including the
brain-
stem
(the part of the brain that controls
involuntary actions such as breathing).
The diagnosis of death under normal
circumstances, when the individual is
not on a
ventilator
,
is based on the
absence of breathing, absence of heart-
beat, and on the pupils being fixed
wide open and unresponsive to light.
W hen an individual has been placed
on a ventilator machine, the criteria
for diagnosing brain death are based
on clear evidence of irreversible dam-
age to the brain; persistent deep
coma
;
no attempts at breathing when the
patient is taken off the ventilator; and
complete lack of brainstem function.
(See also
death, sudden
;
mortality
. )
death rate
See
mortality
.
death rattle
A noisy form of breathing resulting
from the retention of
sputum
(mucous
material) in the airways of a dying per-
son w ho is no longer able to swallow it
or cough it up. Although unpleasant for
the person’s companions, it does not
appear to cause distress to him or her.
death, sudden
Unexpected death in a person w ho pre-
viously seemed to be healthy. The most
common cause
of sudden death in
adults is
cardiac arrest
(cessation of the
heartbeat).
Cardiomyopathy
(disease of
the heart muscle) may cause sudden
death at any age, and its presence may
have been unsuspected. Sudden death
may also occur as a result of
stroke
or in
people
with
unsuspected
myocarditis
(inflammation of the heart muscle) or
pneumonia
.
Less common causes of a
sudden death include
anaphylactic shock
(a severe allergic reaction), a severe
attack of
asthma
,
and
suicide
.
In infants, death without warning is
termed
sudden infant death syndrome
(SIDS), or cot death.
The sudden death of a person of any
age must be reported to the coroner,
who decides whether there should be
an
autopsy
(postmortem examination).
death, sudden infant
W hen a baby is put to bed and later
found dead for no identifiable reason.
See
sudden infant death syndrome (SIDS)
.
debility
Generalized weakness and lack of energy.
It may be due to a physical disorder
(such as
anaemia
) or to a psychological
disorder (such as
depression
) .
debridement
Surgical removal of foreign material
and/or dead, damaged, or infected tis-
sue from a wound or burn in order to
expose healthy tissue. Such treatment
promotes the healthy healing of badly
damaged skin, muscle, and other tis-
sues in the body.
decalcification, dental
The dissolving of minerals in a tooth.
Dental decalcification is the first stage
of tooth decay. It is caused by bacteria
in
plaque
acting on the refined carbo-
hydrates
(mainly sugars) in food to
produce acid, w hich, after prolonged
or repeated exposure, causes changes to
occur on the surface of the tooth. If the
decalcification penetrates the
enamel
layer, it spreads into the dentine and
permits
bacteria to
enter
the inner
pulp. (See also
caries, dental
. )
decay, dental
See
caries, dental
.
decerebrate
The state of being without a function-
ing
cerebrum
,
the main controlling part
of the brain. This situation occurs if the
brainstem
is severed, w hich effectively
isolates the cerebrum.
decidua
The lining of the
uterus
(womb) during
the course of pregnancy. The surface
layers of the decidua are shed from the
body during
childbirth
.
deciduous teeth
See
primary teeth
.
decompensation
The loss of an organ’s ability to meet
the requirements of the body. The term
“ decompensation” is usually used to
describe lessening function in an organ
that has been progressively damaged by
disease.
For
example,
if
the
heart
decompensates, it becomes unable to
maintain an adequate circulation.
The word can also be used with regard
to mental illness, as in
depression
,
when
an individual may lose his or her usual
compensation mechanisms
(strategies
by w hich a person makes up for real or
imagined deficiencies)
and suddenly
deteriorate.
decomposition
The
gradual
breakdown
of
organic
matter (such as food or dead tissue)
into other chemical compounds by way
of bacterial and/or fungal action, heat,
or other processes.
decompression sickness
A hazard of divers and of others who
work in or breathe compressed air or
other mixtures of gases. Decompression
sickness is also called “the bends” . It
results from gas bubbles forming in the
tissues and impeding the flow of blood.
CAUSE
At depth, divers accumulate inert gas in
their tissues from the high-pressure gas
mixture they breathe (see
scuba-diving
medicine
) .
Problems
can
usually
be
avoided by allowing the excess gas in
their tissues to escape slowly into the
lungs during controlled slow ascent or
release of pressure. If the ascent is too
rapid and the pressure falls too quickly,
gas can no longer be held w ithin the
tissues and is released as bubbles.
SYMPTOMS
Bubbles of gas may block blood vessels,
causing symptoms such as skin itching
Pressure
increased
I n e r t g a s d i s s o l v e d in t is s u e
f l u i d s a n d b l o o d
Pressure
reduced
a n d t i s s u e s
How decompression sickness occurs
On ascent, pressure is reduced rapidly and the
gas may form bubbles that may, in turn, cause
symptoms. Divers avoid this by ascending slowly.
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