Mechanical Asphyxia Rahaf - PowerPoint Presentation

Slide1

Mechanical

Asphyxia

Rahaf

Alshorman

Slide2

objectives

Definition

Types of

anoxia

Stages of

mechanical

anoxia

or violent asphyxia

The ‘classical’ features

The autopsy diagnosis of asphyxia

Mechanism of death

Slide3

Definition

failure of cells to receive or utilize oxygen.

The deprivation of oxygen can be partial (hypoxia) or total (anoxia).

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

).

Slide4

Types of

anoxia

:

(1)

Anoxic

anoxia

:

- Ambient.

- Central.

-

Paralytic

.

- Mechanical (violent asphyxia).

- Obstruction of the

blood

flow to the

lungs

.

(2)

Anemic

anoxia

:

-

Chemically

combined

hemoglobin

.

-

Hemolysis

.

-

Hemorrhage

.

(3) Stagnant

anoxia

.

(4)

Histotoxic

anoxia

.

Slide5

Stages 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..

Slide6

The ‘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

.

Slide7

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

.

Slide8

Cyanosis

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

Slide9

The 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.

Slide10

Asphyxial

deaths can be looselygrouped into three categories:

1. Strangulation

2. Suffocation

3. Chemical asphyxia

Slide11

Mechanism of death

1

.

Compression of the neck(Occlusion of neck vein

Compression of the carotid arteries….Reflex vagal inhibition) (hanging and strangulation)

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

Slide12

Strangulation …. Pressure on the neck

Hanging

Strangulation with

Ligature

Throttling (manual asphyxia)

Slide13

Hanging

Definition

:

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

.

- Transsection of the spinal

cord

(

judicial

hanging

).

Slide14

Types 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

or running

noose

Always

running

noose

Rope

marks

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

Slide15

Slide16

Post-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

Slide17

Strangulation with Ligature

Definition

:

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

.

Slide18

Postmortem

picture

of strangulation:

(1) General

(2)

Special

features

All are neck

signs

:

- Ligature marks:

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

Slide19

Slide20

Throttling

«

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

.

Slide21

Postmortem

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

Slide22

Slide23

The amount of force required to compress neck structures is estimated as:

Jugular vein: 2 kg

Carotid artery: 5 kg

Trachea: 9 kg

Vertebral artery: 30 kg.

This implies that venous flow is decreased before arterial and airway obstruction occurs.

Force required for fractures of:

thyroid cartilage lamina:14.3 kg

cricoid cartilage: 18.8 kg

Slide24

SUFFOCATION

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

.

Slide25

Rapid 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.

Slide26

Slide27

Six general forms of suffocation:

1.

Entrapment/environmental suffocation:

an individual inadvertently enters an area

where there is gross deficiency of oxygen.

2.

Smothering

3

. Mechanical asphyxia

4

. Choking

5

. Gagging

6

. Drowning

Slide28

Smothering

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

.

**

Homicidal

,

suicidal

or

accidental

Slide29

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, there may be

bruises and abrasions to the face, on the lips or

inside the mouth (where lips are pressed against teeth).

Slide30

Slide31

Mechanical 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

Slide32

Slide33

Postmortem

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

Slide34

Slide35

GAGGING

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.

Slide36

Slide37

Choking

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

Slide38

Slide39

Drowning

Definition

:

It

is

the

mechanical

anoxic

death

due to

submersion of the

respiratory

openings

under

water.

Wet

Drowning:water

enter the

lungs

Dry

Drowning:water

enter the

just

th

E

URT but not the

lungs

Causes of

death

:

- Direct causes:

mechanical

anoxia

- Indirect causes:

. Reflex

cardiac

inhibition due to vagal stimulation

. Head

injury

or

other

fatal injuries.

Slide40

Fresh vs. salt water drowning:

Fresh:

Due to less salinity.. osmotic pressure effects:

1.dilution of plasma=>rupture of RBCs=>release of K-(hyperkalemia)=>

ventricular fibrillation

2.Rapid absorption of water through alveolar membrane(hemodilution)=>overload to heart=>

ventricular fibrillation

=>heart failure=>death in 4-5 min

Slide41

Salt:

Due to high salinity=>osmotic imbalance=>water enters the lung from the blood=>

* 1.severe edema of the lungs(Pulmonary edema)

2.hemoconcentration

=>circulatory shock=>cardiac asystole=>DEATH

Death

in 8-12 min

*

The cause of Death is Pulmonary Edema

Slide42

Slide43

Posrmortem

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

-

Washerwoman

skin -

Postmortem

injuries

. Affection of

postmortem

changes due to

presence

in water:

-

Cooling

-

hypostasis

-

adipocere

-

putrefaction

**

Homicidal

,

suicidal

or

accidental

Slide44

Abnormal goose skin

Froth

Washerweman skin

Slide45

Chemical

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

Hydrogen 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

Slide46

Thank You