Forensic Toxicology- Asphyxiants is a substance that can cause unconsciousness or death by suffocation.

1. Dr Anu Mariam Varghese
3rd MD Scholar
Dept of Agadatantra
GAVC, TVM

3. POISON
Corrosives Irritants Systemic Miscellaneous
a. Cerebral
b. Spinal
c. Peripheral
d. Cardiovascular
e. Asphyxiants

5.  An asphyxiant is a substance that can
cause unconsciousness or death by
suffocation.
 Substances that cause asphyxial death –
asphyxiants

6.  Henderson and Haggard
 1. Irritants
 2. Chemical asphyxiants
 3. Simple asphyxiants
 4. Volatile drugs
 5. Systemic poisons

7. 1. Irritants
 Gases injure air passages/lungs/both
 Produce inflammatory change
 Smoke, tear gas, ammonia, formaldehyde, chlorine
2. Chemical asphyxiants
 Combines with Hb --> prevents oxygen from reaching
tissues
 CO, Hydrogen sulphide, cyanide
3. Simple asphyxiants
 Inert gases
 When breathed in high con. Acts mechanically by
excluding O2
 CO2, methane, nitrous oxide, N2

8. 4. Volatile drugs
 No irritant effect on air passages.
 Acts after absorption into blood.
 Toxic to liver, kidney and nervous system
 Aliphatic, aromatic, halogenated hydrocarbons
5. Systemic poisons
 Insecticides

9.  CARBON MONOXIDE - CO
 CARBON DIOXIDE - CO2
 HYDROGEN SULPHIDE - H2S

11. FEATURES
Colorless, tasteless, non irritative gas produces due to
incomplete combustion of carbon.
 Insoluble in water.
 Burns with blue flame
 Lighter than air
 Mixture of CO with 2 ½ times its volume of air –
highly explosive in presence of flame

13.  Common source - coal gas, smoke from
fires, fumes from
defective heating
appliances.
 Industry - 20%
 Smoking

14. CO in
inspired air
Absorbed into
blood through
alveoli
Reaches
blood

17. COHb
Tissues not able to
dissociate COHb
and use O2 in
oxyhaemoglobin
Hypoxia

18.  Displaces oxygen from its combination with
hemoglobin and forms relatively stable compound
carboxyhemoglobin thus leading to hypoxia.(
affinity 200 to 300 times greater).
 CO affinity to myoglobin (40 times greater) may
cause direct myocardial depression.
 Act as chemical asphyxiants produce death due to
anaemic anoxia.
 Interfers with intercellular respiration.

19.  Eliminated through lungs
 1% is metabolized into CO2
 Not lost through skin, bile, perspiration, urine
or faeces.
 Not absorbed by a body after death

23. • Often mistaken for symptoms
of influenza or illness caused
by contaminated food..
• Effects are simply those of
suboxia.
• Bullae are localised over
calves, buttocks, wrists and
knees by external pressure.
• Death usually occurs when
80% of Hb is saturated with
CO.
• CO automatism
Tendency of the dying victim to
wild, erratic, swinging
movements inside the room,
disturbing clothing and
furniture which gives an
impression of violent struggle.
• CO pass from maternal to
fetal blood, produce
intrauterine death (˃ 10 to
15 %)

24.  Blood under the skin and in tissues will be
cherry red due to formation of carboxy-
haemoglobin.

25. • Headache, confusion
• Paraesthesia
• Visual disturbances
• HTN, Hyperthermia
• Mental Retardation.
• Parkinsonism
• Psychosis

26.  Remove patient to fresh air
 Conscious and breathing, no treatment
 COHb level >25% should be treated
 Provide 100% oxygen
 Endotracheal intubation
 CO2 should not be given
 Gastric lavage in early stage
 Whole blood transfusion
 Complete rest for 48 hrs

27.  Cherry red appearance of skin, mucous, conjunctiva,
nail bed.
 Anemic cont.. - color pink
 Dark coloured victims - masked
 Color will not be changed by embalming or
preservation by formalin
 During decomposition
› Cherry red -> dark green -> brown

28.  Blistering of skin of dependent area.
 Congestion of lungs with pink fluid blood
 Pulmonary edema.
 Bilateral symmetrical necrosis and cavitation
of basal ganglia in putamen and globus
pallidus
 Ring shaped hemorrhages in white matter of
brain.

30.  Suicide is rare
 Accidental is most common
Exposure to exhaust gas of petrol engine
Exposure to gas in mines
Incomplete combustion of wood, charcoal or coal
 Homicide is uncommon
 Unless victim is alcoholic or child

31. SUICIDE BY CO POISONONG

33.  Features
 Heavy, colorless gas
 Faintly sweet odour
 Atmospheric air 0.033% CO2’
 Product of complete combustion of carbon.
 Seen at manholes, ship holds, old wells
 Action
 Not toxic
 Simple asphyxiant- Preventing tissue from obtaining
oxygen.

35. ˃ 5 % - Laboured breathing, Mental confusion
˃ 10% - Ataxia and unconsciousness
˃ 40% - Dyspnea, Muscular weakness
˃ 50 % - Dyspnea, Fullness in head, Ringing in
ear, loss of muscular power, unconsciousness,
coma, death.
˃ 60-80% - Unconsciousness and rapid death.

36.  Artificial respiration
 Free O2
 Cardiac stimulants

37.  Marked cyanosis
 Congestion
 Suffusion of eyes
 Dilation of the pupils
 Petechial hemorrhages

38.  Accidental

40. FEATURES
 Colorless, heavy, flammable
 Exposure to lower con. smell of rotten eggs is
detected.
 Formed during decomposition of organic matter
containing sulphur.
 Poisoning due to inhalation
 ACTION
 Does not combine with Hb
 Interferes with cellular respiration by inhibiting the
action of cytochrome oxidase.
 SEWER GAS - H2S + CO2 + CH4

42.  Great dilution Feeling of dullness and
sleepiness, death may occur during sleep
 Weak concentration Cough, giddiness,
nausea, cyanosis of face, muscular weakness…
 Moderate concentration metabolic
acidosis, CNS, respiratory and myocardial depression
Death from paralysis of respiratory centre.

43.  Chronic low level absorption
 Reduced lung function
 Headache
 Depression
 Personality changes
 Chronic eye irritation

44. TREATMENT
 Patient is removed to fresh air
 Artificial respiration
 100% O2
 Excretion of sulphide.
 Amyl nitrate inhalation and sodium nitrate infusion.
POST MORTEM APPEARENCES
 Rotten egg odour is given off
 General signs of asphyxia
 Color of blood, viscera, bronchial secretions is greenish
purple