Asphyxiants

Define asphyxiant

A substance that impairs the ability of the body to absorb or utilise oxygen resulting in suffocation.

Impaired oxygen deliver to cells reults in cellular hypoxia and impaired ATP production. If prolonged can reult in cell death

Simple asphyxiant

Causes hypoxia by displacing oxygen and lowering the partial pressure of oxygen

Chemical Asphyxiant

causes hypoxia by interfering with cellular respiration.

Affects mitochondrial function and haemoglobin binding

Carbon Monoxide

Chemical Asphyxiant

Binds 200 x more strongly to Hb than Oxygen

Hydrogen Cyanide

Binds mitochondrial enzyme cytochrome a3 and blocks ATP production(Oxidative phosphorylation)/ electron transport chain, anaerobic metabolism and lactic acidosis

Cellular respiration affected

Hydrogen Sulphide

inhibits cytochome oxidase enzymes in mitochondria resulting in anaerobic respiration

inhibits cellular respiration

carbon monoxide

Reducing oxygen carrying capacity by binding to HB strongly

Binds to myoglobin reducing cardiac output

Binds to cytochrome oxidase

Half life of CO

ROOM AIR - 4.5 HOURS

100% 02 - 1 HOUR

HYPERBARIC - 20 MIN

Rotten egg odour

low concentrations of Hydrogen Sulphide

Olfactory nerve paralysis at high levels of exposure

Bitter almond odour

Hydrogen cyanide

Also olfactory paralysis at high concentrations

CO FORMATION

INCOMPLETE COMBUSTION OF CARBON CONTAINING FUELS

COLOURLESS AND ODOURLESS

TREATED WITH 100% O2 FOR 6 HOURS

CARBOXYHAEMOGLOBIN INTERPRETATION

A COHb concentration of more than 2% in a nonsmoker and >10% in a smoker confirms exposure to CO

1% NON SMOKER

4% SMOKER

IMPORTANT CONSIDERATIONS

CONFINED SPACE

SOURCE OF GAS

DOSE/CONCENTRATION , DURATION/TIME

COHB CONCENTRATIONS

SYMPTOMS ( RESP AND CNS START > 10%)

APPROACH 60% - SYNCOPE AND SEIZURES

APPROACH 80% - DEATH

GATHER NEAR THE GROUND

C02, ETHANE

PREVENTION

OXYGEN CONCENTRATION DETECTION DEVICES TO CHECK AREA , AND IDENTIFYING AT RISK AREAS

SAFETY HARNASSES FOR WORKERS

SELF CONTAINED BREATHING APPARATUS

EMERGENCY OXYGEN ON HAND

OHSA DEFINITION OF OXYGEN DEFICIENT ENVIRONEMENT

<19.5%

ASYMPTOMATIC TO SOME SYMPTOMS AFFECTING THE CNS AND RESPIRATORY SYSTEM BETWEEN 16-19.5

NB: DEATH BELOW 6%