Definition Types of anoxia Stages of mechanical anoxia or violent asphyxia The classical features The autopsy diagnosis of asphyxia Mechanism of death Definition It is ID: 914493
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Slide1
Mechanical Asphyxia
Slide2objective
Definition
Types of
anoxia
Stages of
mechanical
anoxia
or violent asphyxia::
The ‘classical’ features
The autopsy diagnosis of 'asphyxia‘
Mechanism of death
Slide3Definition
It
is
any
condition
that
leads
to:
-
reduction
of the
oxygen
supply
to the
blood
and the tissues
below
the
the
normal
physiological
level
(
hypoxia
).
-
elevation
of CO2 in the
blood
(
hypercapnia
).
**
Hypoxia
means
(
low
oxygen
)
while
anoxia
means
(
without
oxygen
).
Slide4Types of
anoxia
:
(1)
Anoxic
anoxia
:
-
Ambient
.
بيئة
- Central.
-
Paralytic
.
- Mechanical (violent asphyxia).
- Obstruction of the
blood
flow to the
lungs
.
(2)
Anemic
anoxia
:
-
Chemically
combined
hemoglobin
.
-
Hemolysis
.
-
Hemorrhage
.
(3) Stagnant
anoxia
.
راكد
(4)
Histotoxic
anoxia
.
Slide5Stages of
mechanical
anoxia
or violent asphyxia:
Three
stages:
(1) Stage of
forced
respiration:
- It
is
due to stimulation of the
respiratory
center.
-
Clinical
picture
:
DYSPNEA
(2) Stage of convulsions:
- It
is
due to
cerebral
irritation.
-
Clinical
picture
:
CONVULSIONS,
CYANOSIS, HYPERTENSION
, LOSS OF CONSCIOUSNESS, CONSTRICTED PUPILS.
(3) Stage of
paralysis
:
-
Clinical
picture
:
LOSS OF CONSCIOUSNESS, FLACCID MUSCLES & LOST REFLEXES, DEEP CYANOSIS, DILATED PUPILS, IRREGULAR BREATHING (
Cheyne
-Stokes respiration).
**
Death
occurs
in about
5 minutes..
Slide6The ‘classical’ features
are found where the
air passages are obstructed
by pressure applied to the neck or to the chest .
The
classical features of ‘asphyxia
’ are:(
although not diagnostic, are important.)
1
congestion of the face;
2
oedema
of the face;
3
cyanosis (blueness) of the skin of the face
4
petechial
haemorrhages
in the skin of the face and the eyes
.
A
fifth
feature – increased fluidity of the blood – is now not accepted.
Very non-specific, very unreliable
The slower the death, the more prominent
asphyxial
signs
.
Petechiae
are
pinpoint hemorrhages
produced
by rupture
of small vessels, predominantly
small
venules
.
Rupture appears to be
mechanical in etiology and is caused by sudden over distention following abrupt increases in intravascular pressure
These are
most common
in the
visceral pleura and
epicardium
. also seen in the
conjunctivae and
sclerae
.
Slide8Cyanosis
caused by an increase in the amount of
reduced hemoglobin
.
It does not become observable until at
least 5 g of reduced hemoglobin is present.
Congestion
is the
red appearance of the skin of the face and head
.
It is due to the
filling of the venous system when compression of the neck or some other obstruction prevents venous return to the heart.
Oedema
is the
swelling of the tissues
due
to transudation of fluid from the veins caused by the increased venous pressure
as a result of obstruction of venous return to the heart
Slide9Slide10Slide11Slide12Slide13Slide14Slide15The autopsy diagnosis of 'asphyxia'
Sings of asphyxia is very
unspecific
.
Even co-existence of these findings,
does not prove that death resulted from mechanical asphyxia.
post-mortem diagnosis –
blood gases – impossible – very rapid changes.
careful assessment of the history and circumstances of the death + exclusion of other causes + cautious evaluation of the signs
diagnosis.
Most important – cause for airway obstruction.
Slide16Asphyxial
deaths can be loosely grouped into three categories:
1. Suffocation
2. Strangulation
3. Chemical asphyxia
Slide17Mechanism of death
a combination of these
1)
Compression of the neck(Occlusion of neck vein
Compression of the carotid arteries….Reflex
vagal
inhibition
) (hanging
andstrangulation
)
2. Blockage of the airway (suffocation, gagging)
3. Compression of the chest, neck, or face (postural
or positional asphyxia)
4. Chemical and lack of available oxygen in the
atmosphere
Slide18Strangulation …. Pressure on the neck
Hanging
Strangulation
with
Ligature
Throttling (manual asphyxia)
Slide19Post-mortem
picture
:
(1) General
(2)
Special
features
-
Protrusion
of the
tongue
.
- Dribbling of saliva.
-
Hypostasis
of the
lower
half
of the body.
- Neck
signs
:
.
Elongated
and the
head
is
tilted
to the opposite
side
of suspension point.
.
Ligature marks (
HIGH UP
in the neck,
OBLIQUE
,
INCOMPLETE
, has an
IMPRINT
of the ligature).
**
Homicidal
,
suicidal
or
accidental
Slide20Hanging
Definition
:
شنق
It
is
the
mechanical
anoxic
death
due to
suspension
of the body
from
the neck by a ligature.
Causes of
death
:
-
Cerebral
ischemia
.
- Vagal
cardiac
inhibition.
- Mechanical
anoxia
.
-
Transection
of the spinal
cord
(
judicial
hanging
).
Slide21Types of
hanging
Point of
comparison
COMPLETE
HANGING
INCOMPLETE
HANGING
Other
name
High point
hanging
Low
point
hanging
Touching
the
ground
Negative
Positive
Circumstances
Presence
of a
near
-by table or
chair
Negative
Main cause of
death
Cerebral
ischemia
Asphyxia
Face
Less
congested
,
sometimes
pale
Markedly
congested
Hypostasis
Lower
half
of the body
According
to the part
touching
the
ground
Type of
knot
Fixed
knot
عقدة
or running
noose
Always
running
noose
Rope
marks
حبل
Incomplete
with
fixed
knot
Above
thyroid
cartilage
Oblique
Deep
and fades
gradually
towards
suspension point
-Complete
-
Below
thyroid
cartilage
-Transverse
-
Deep
all
through
Dribbling of saliva
Positive
Negative
Tear
in
carotid
intima
Positive
Negative
Hyoid
bone
If
fractured
:
outwards
If
fractured
:
inwards
Slide22Slide23Slide24Slide25Slide26Slide27Slide28Slide29Slide30Slide31Slide32Slide33Slide34Slide35Slide36Slide37Slide38Strangulation
with
Ligature
Definition
:
خنق
It
is
the
mechanical
anoxic
death
caused
by constriction of the neck by a ligature
occluding
the
air passages
from
outside
.
Causes of
death
:
- Mechanical
anoxia
.
- Reflex
cardiac
inhibition.
-
Delayed
edema
of the
glottis
and
choking
.
Slide39Postmortem
picture
of strangulation:
(1) General
(2)
Special
features
All are neck
signs
:
- Ligature marks:
زي
incomplete hanging
.
Low
in the neck
below
the
thyroid
cartilage.
. Transverse.
. Complete.
.
Deep
all
through
.
. Abrasions and contusions
taking
the
shape
of the
ligating
material
.
-
Inward
fracture of the
hyoid
bone
and the
thyroid
cartilage
may
be
fractured
.
- Contusions and
lacerations
of the neck muscles.
**
Homicidal
,
suicidal
or
accidental
Slide40Slide41Slide42Slide43Slide44Slide45Slide46Slide47Slide48Slide49Slide50Slide51Slide52Slide53Slide54Throttling
«
Manual
strangulation»
Definition
:
It
is
the
mechanical
anoxic
death
caused
by constriction of the neck by the hand
occluding
the air passages
from
outside
.
Causes of
death
:
- Mechanical
anoxia
.
- Reflex
cardiac
inhibition.
-
Cerebral
anoxia
.
-
Delayed
glottic
edema
and
choking
.
Slide55Postmortem
picture
:
(1) General
(2)
Special
features
All are neck
signs
-
Multiple contusions and
fingernail
abrasions
.
-
Inward
fracture of the
hyoid
bone
(
it
is
the
most
common
cause of
hyoid
bone
fracture
) and fracture of the
thyroid
cartilage.
- Contusions of the
deep
tissues of the neck.
**
Homicidal
,
suicidal
or
accidental
Slide56Slide57Slide58Slide59SUFFOCATION
Situations in which
accumulations of irrespirable gases occur are commonly industrial or agricultural
;
they may be found in the deep tanks of ships where rust formation has removed oxygen,
in farm silos containing grain, or
in deep wells in chalk where carbon dioxide has accumulated.
The
individual entering these situations without protective equipment will be rendered unconscious extremely quickly and will die rapidly
unless removed from the hypoxic environment.
In all these situations,
asphyxial signs may be minimal as collapse and death may be so rapid
.
Slide60Rapid deaths are also reported when
a plastic bag
is placed over the head, either as a deliberate suicidal act or accidentally by children. Typically, no ‘classic signs’ are seen and the face is usually
pale
when the bag is removed. The bag need not be tied around the neck to be effective.
Exit’ suicide with a plastic bag. The face is usually
pale and devoid of asphyxial signs.
Slide61suffocation:
six general forms of suffocation:
1. Entrapment/environmental suffocation
2. Smothering
3. Choking
4. Mechanical asphyxia
5. Suffocating gases
environmental suffocation
, an individual inadvertently enters an area
where there is gross deficiency of oxygen.
Slide62Smothering
Definition
:
It
is
the
mechanical
anoxic
death
caused
by
occlusion of the
external
respiratory
openings
by the hand or soft
objects
.
Causes of
death
:
Mechanical
anoxia
Postmortem
picture
of
smothering
:
(1) General
(2)
Special
features
- Multiple contusions and
fingernail
abrasions.
- Contusions in the buccal
mucosa
.
- Ventral
hypostasis
in
cot
death
.
المهد
**
Homicidal
,
suicidal
or
accidental
Slide63SMOTHERING
Smothering with a pillow or other object (including a hand) pressed over the nose and mouth will only
very rarely cause any petechiae
,
any significant cyanosis or congestion unless the victim struggles and fights for breath against the obstructed airways.
Smothering may be virtually impossible to
diagnose if it is applied to those who cannot or
do not resist – the old, the infirm or the very
young. If the
victim does struggle
كفاح
, there may be
bruises and abrasions to the face, on the lips or
inside the mouth
(where lips are pressed against
teeth).
Slide64Slide65Slide66Slide67Slide68Slide69Mechanical asphyxia is almost always accidental in manner. It can be
subdivided into three types:
Traumatic Asphyxia
Traumatic asphyxia occurs when a heavy weight presses down on an individual’s
chest or upper abdomen, making respiration impossible.
Causes of
death
:
-
Mechanical
anoxia
.
-
Injury
to vital
organs
Positional asphyxia
Positional asphyxia is virtually always an
accident
and is associated with
alcohol or drug intoxication
. In this entity,
individuals become trapped in
restricted spaces, where, because of the position of their bodies, they cannot
move out of that area or position.
Riot-crush
Riot-crush, as the name implies, occurs in riots, when the chest is compressed
by stampeding people piling on top of each other. Respiratory movements
are, thus, prohibited by this human pile
Slide70Postmortem
picture
of
traumatic
asphyxia
(1) General
(2)
Special
features
- Contusions and abrasions of the
chest
and abdomen.
- Fracture
ribs
.
- Rupture of
internal
organs
.
- Line of
demarcation
between
the
discolored
upper
part of the body and the
lower
part.
**
Homicidal
,
suicidal
or
accidental
Slide71Slide72GAGGING
The
air passages may be obstructed when a cloth or soft object is pushed into the mouth, or placed across the mouth, often during a robbery when the victim is tied up and the cloth is used to ensure
their silence
. At
first, breathing can
take place via the nose, but as time
goes on, nasal mucus and edema
close the posterior nares and
progressive asphyxia develops
.
Slide73Choking
Definition
:
It
is
the
mechanical
anoxic
death
caused
by occlusion of the
respiratory
passages
from
inside
.
Causes of
death
:
- Reflex
cardiac
inhibition
- Mechanical
anoxia
Types:
-
Pathological
- Non-
pathological
**
Homicidal
,
suicidal
or
accidental
Slide74Slide75Slide76Drowning
Definition
:
It
is
the
mechanical
anoxic
death
due to
submersion of the
respiratory
openings
under
water.
Causes of
death
:
- Direct causes:
mechanical
anoxia
- Indirect causes:
. Reflex
cardiac
inhibition due to vagal stimulation
. Head
injury
or
other
fatal injuries.
Slide77Posrmortem
picture
of
drowning
-
Sure
external
signs
:
.
Froth
.
Cadaveric
spasm
-
Probable
external
signs
:
.
Related
to
anoxic
anoxia
:
cyanosis
.
Related
to
presence
of the body in water:
skin
is
pale&
wet
Goose
skin
اوزة
Washerwoman
skin
Postmortem
injuries
. Affection of
postmortem
changes due to
presence
in water:
Cooling
,
hypostasis
,
adipocere
,
putrefaction
**
Homicidal
,
suicidal
or
accidental
Slide78Slide79Chemical
Asphyxiants
In chemical asphyxia, inhalation of a gaseous compound prevents utilization
of oxygen at the cellular level. The most common chemical
asphyxiant
encountered by a medical examiner is carbon monoxide.
Hydrogen cyanide
Hydrgen
florid
Sexual Asphyxia (Autoerotic Asphyxia, Autoerotic Deaths)
These are
asphyxial
deaths, principally caused by hanging, in which transitory anoxia is intentionally induced to enhance sexual
arousement
produced by masturbation
Slide80References
DiMaio
Forensic Pathology
Forensic-Color Atlas of forensic pathology
Simpsons forensic pathology
Slide81Thank You