Full chapter for Bs Student Asphyxiants.pdf

Biochemistry for bs

1. Asphyxiants (Irrespirable Gases)
By: Abdur Rehman
PhD Scholar
Biochemistry
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2. Asphyxiants
•Asphyxiants mainly produce respiratory
embarrassment; important asphyxiants include
–Carbon Monoxide (CO)
•Reduce oxygen carrying capacity
–Carbon dioxide (CO2)
•Lack of oxygen in tissue
–Hydrogen Sulphide(H2S)
•Paralyses respiratory center
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3. Carbon Monoxide (CO)
•Colorless, odorless, non irritant gas
•Cant perceived by senses
•Incomplete combustion of carbon & organic
matter=Carbon monoxide
•Sources; illuminating gas, oil heater, gas heater,
vehicle engine etc
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4. Carbon Monoxide (CO) cont..
•CO has 200-300 time higher affinity to Oxygen
•Displace oxygen form carboxy hemoglobin more
stable
•Ultimately result in anoxia
•Recent studies showed dissolved CO interfere vital
enzyme
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5. Sign & Symptoms
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Carbon Monoxide Poisoning: Here’s What You Need To Know | Just Boilersdated 11-
07-2021

6. Sign & Symptoms
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COHb
% Saturation
Symptoms
0-10 No appreciable Symptoms
10-20 Breath shortness, mild headache, flushed skin
20-30
Throbbing headache, buzzing in ear, dulling of senses, muscle
weakness
30-40
Severe headache, nausea, vomiting, breathlessness, incoordination,
muscle weakness, dim vision, impaired judgment
40-50
Symptoms intensified, may be mistaken with drunk, mental confusion,
memory loss, palpitation and dyspnea
50-70
Intermittent asphyxia convulsion, coma, Cheyne-Stokes respiration,
respiratory paralysis & death
>70 Rapidly fatal due to respiratory arrest

7. Diagnosis of CO
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https://www.verywellhealth.com/carbon-monoxide-poisoning-diagnosis

8. Blood Test
•A layer of 1-2 cm paraffin added immediately after
blood collection
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Method 1: a suspected sample diluted with
four times its volume of water & add few
drops of 3 % aqueous tannic acid to
solution and shaken well
If >10 % CO present, it form pinkish white
precipitate

9. Blood Test
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Method 2: A suspected blood sample diluted
with 20 times its volume of water & 10
drops of 10 % caustic soda added to it.
Normal blood becomes greenish brown but
Blood containing >10 % CO retains its
bright red color as no methemoglobin is
formed

10. Carbon Dioxide Poisoning
•This is heavy, colorless, odorless & Poison gas
•Result from complete combustion of carbon
containing compounds
•Formed due to fermentation & decomposition of
organic matter
•Sources; refrigerating plants, manholes, wells, re-
breathing close spaces
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11. CO2 Poisoning cont…
•Pure CO2 inhalation may cause vagal inhibitory
response, spasm of glottis , instant death
•> 50%CO2 may result immediate unconsciousness &
death from deficiency of oxygen supply to brain &
tissues
•Unexpected death from CO2 under anesthesia
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12. Hydrogen SulphidePoisoning
•Sulphurated gas; a colorless gas with rotten egg smell
•Found if Sulphur containing compound under decay
•Such as sewers, tannery vats , formed during artificial silk
manufacturing etc
•Formed in human intestine during life and due to
putrefaction after death
•Converts oxyhemoglobin to methemoglobin &
sulphmethemoglobinafter death
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13. H2S Poisoning Cont..
•If pure H2S inhaled death occur at once
•Result in paralysis of the respiratory Centre
•A 0.2 % concentration in air proved fatal in few
minutes
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14. Reference
•Text book of Medical Jurisprudence, Forensic medicine and Toxicology, BV SubrahmanymSeventh edition
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