3 - Mechanical asphyxia (chapter 7)

Mechanical asphyxia is defined as:

pathophysiological processes that associate the decrease or lack of circulating oxygen, respectively hypoxia or anoxia

classification asphyxia

• by production circumstances - violent or patho

• by respiratory process stages - hypoxic, transport, alteration @ alveolo-cap membrane, from O2 deficiency @ tissues, anoxic

classification mechanical hypoxic asphyxia

• obstruction - suffocation, w/ foreign body or aspiration

• compression - on thorax-abd, on cervical region (hanging, strangulation, choking)

macro external exam asphyxia

• cyanosis - face, extremities, patchy, uneven, intensity depends on anoxic state duration

• cadaveric lividities - prematurely developed, blue-purple, on large surfaces

• asphyxiated hemorrhagic petechiae - purple, black hemorrhagic spots, on lividities, subconjunctiva, lips

• sphincteric incontinence

• mydriasis

• prolabatic tongue bw dental arches

internal macro exam asphyxia

• marked, generalized visceral blood stasis

• asphyxiated petechiae - in serosa, meninges, cerebral white matter, pleural (‘Tardieu’)

• blood is liquid, dark in colour, increased CO2 and catecholamines

micro aspects asphyxia (Spielmayer and Kernbach anoxic imprint)

• organ stasis and edema

• endotheliosis

• rupture cap. and interalveolar septa

• hydropicnovacuolar dystrophy

• fragmentation myocardial fibers

tanatochemical

In mechanical asphyxiation, death can occur through the following mechanisms:

• acute anoxia (lack O2)

• hemodynamic mechanism (compression vasc structures in cervical region)

• reflex mechanism (compression carotid sinus)

• fx cervcal spine (only in hanging)

classification hanging

• according to node position - typical (post cervical node, nape of neck), atypical (node anywhere else)

• according to corpse position - complete (w/o support points, totally suspended), incomplete (body has support point around it)

ligature mark findings hanging

• parchment like skin depression, yellow-brown, uneven depth

• upper 1/3 of neck, submandibular

• circular, circular, interrupted next to node

• oblique trajectory, towards node

• excoriated edges, ecchymosis

• hemorrhagic infiltration in subcutaneous tissue, muscles

• putrefaction-resistant lesion

3 noose categories

• soft - superficial ditches

• semi-hard (electric cable, rope)

• hard (wire, chain) - deep ditthces

2 node categories in asphyxia

fixed

sliding

int exam asphyxia

• hemorrhagic infiltration in soft tissues of neck

• rare hyoid bone fx/laryngeal thyroid cartilage

• carotid lesions - longitudinal hemorrhagic infiltration in outer tunic, hemorrhagic suffusions in intima, transverse bursts in intima (Amussat’s sign)

• rare axis fx - by hyperextension cervical spine

strangulation

Form of mechanical asphyxia caused by external compression of the neck with a cord that forms at this level a circular shape, which is actively tightened, being controlled by an external force

ext ema strangulation

• strangulation mark - parchmentlike skin depression in middle 1/3 of neck, horizontal trajectory, complete ciruclar appearance

• yellow-brown, uniform

• ± ecchymosis/excoriations in vicinity (victims attempt to free themselves)

• ext stigmas, signs violence

int exam strangulation

hemorrhagic infiltration into soft tissues of neck

fx thyroid cartilage/hyoid bone

choking vs strangulation- legal issues

choking is exclusively homicide

strangulation can be suicide (rare)

ex exam choking

oval ecchymosis (fingers), crescent excoriations (nails)

• if one-handed - one side of the neck there is an oval ecchymosis flanked by a crescent excoriation, other side of the neck four ecchymosis flanked by crescent excoriations

int exam strangulation

• hemorrhagic infiltration neck muscles

• fx laryngeal cartilage, hyoid bone

thoraco-abd compression

Form of mechanical asphyxia, caused by exerting a high pressure on the thorax and/or upper abdomen with the blockage, by the pressure exerted, of the diaphragmatic excursion (the main respiratory muscle) and the blockage of the pulmonary compliance

legal issues thoraco-abd compression

• accidental

• criminal

ext exam thoraco-abd compression

signs intense asphyxia (intense cyanosis face, petechiae)

int exam thoraco-abd compression

sternal fx, bilat rib fx

lungs - carmine edema lungs

thoracic/abd organs injuries (contusions, pul abd and cardiac rupture)

in what asphyxia method do we have discordance between reduced skin lesions and severe internal lesions!

thoraco-abd compression

suffocation

Mechanical asphyxia achieved by concomitant coverage of the external respiratory orifices (nostrils, oral cavity) making it impossible for air to enter the airways into the lungs

methods suffocation

by hand, pushing face into soft objects

damp cloth to resp tract, wrapping head w/ sheet

fixing adhesive tapes on resp orifices

inserting head into plastic bag

necroptic aspects suffocation

• oval ecchymosis, perioronasal semilunar excoriations (unless soft object used)

• deformation/fx nasal pyramid, parchmentlike excoriated areas

• hemorrhagic infiltration on inner lips

• lint, flakes in oral cavity, nostrils

drowning

Form of mechanical asphyxia produced by stenosis or internal obstruction of the airways (larynx, trachea, bronchi and bronchial tree) with various foreign bodies, of external or internal origin; total obstruction of the lumen is not necessary for death to occur

legal issues in drowning

• accidental - milk asphyxia in babies, kids, drunkenness, bolus

• homicide

  • rarely suicide

materials of drowning mechanism

• bolus obstruction (during meals)

  • aspiration obstruction (regurgitated gastric contents, Mendelson sd, from alcohol), of blood (craniofacial trauma, rupture esophageal varices)

pathophysio drowning (by submersion)

• voluntary apnea phase (1 minute)

• inspiratory dyspnea w/ involuntary inspiration (increase CO2 >55mmHg, decrease O2 <100mmHg)

• exp dyspnea - defensive reflex, coughs then new involtunary inspiration, after 3 repetitions the person is unconscious

• convulsions

• terminal, wide, rare breaths

• cardiac arrest

• death after 5m

necroptic aspects drowning

vital rxn

• fungal complications - pink/gray/white foam on mouth and nose, dense pearly

• hydroaerial pul emphysema - by rupture interalveolar septa, enlarged lungs, costal imprints on surface, spongy

• Paltauf asphyxiated petechia eon pleura

• fluid in pleural cavities by resorption aspirated fluid

• sand/mud/alge in upper resp tract

• white foam in trachea and bronchi

• liquid in GIT

tardieau vs paltauf asphyxiated petechiae

paltauf is bigger and more purple

cryoscopic point determination in drowning corpse

• blood freezing point, normal 0.57 dg

• in fresh water - molecular c% lower

• salt water - higher

aquatic plankton and diatoms research in drowning corpse

resistent to putrefaction

in organs w/ /terminal circ (spleen, kidney, BM)

allows establishment season of drowning and if drowning occured in the water in which body found

plankton vs diatoms

plankton - all living organisms in water

diatoms - unicell algae