Inhalational Inhalational injuriesinjuries

H.R.Sarreshtahdar, MDH.R.Sarreshtahdar, MDOccupational Medicine SpecialistOccupational Medicine Specialist

Irritant lung reactionsIrritant lung reactions Many gases, fumes, and aerosols are

directly toxic to the respiratory tract Site of effect is determined by:

Water solubility High solubility (ammonia): irritation of upper

respiratory Low solubility (O3): irritation of lower respiratory

Particle size Large particles (>10μm): upper respiratory Medium particles (3-10 μm): airways Small particles (<3 μm): lung parenchyma

Irritant lung reactionsIrritant lung reactions Examples of some irritants:

Ammonia HCl SO2 NOx Phosgene O3

Clinical findings: Immediate irritation of upper respiratory tract

to late pneumonitis and pulmonary edema

ManagementManagement Immediately obtain ABG + O2 therapy Take a history (esp. attention to chemical

asphyxiants) Examine eyes, nose, pharynx for evidence of

burns Auscultate lungs Baseline spirometry if subject is capable Baseline CXray Admit to hospital Observe for 24-48h

Simple AsphyxiantsSimple Asphyxiants Gases:

Methane, ethane, propane Ethylene, propylene, acethylene CO2 N2 NO

Effect: reduction of fractional inspiratory concentration of O2→ hypoxia

No toxic effects

Simple AsphyxiantsSimple Asphyxiants Exposure:

typically in confined spaces (storage tanks, mines)

For gases heavier than air any low-lying semi-closed space with little air movement is dangerous

Methane (mining)CO2 (food preservation, manufacture of dry ice,

…)N2 (underwater work, mining, metallurgic

operations, pressurizing oil wells)

Simple AsphyxiantsSimple Asphyxiants Clinical findings: Related on:

Asphyxiant concentration Level of physical activity Underlying medical status

Normal air O2: 21% O2 (10-16%): tachycardia, tachypnea,

exercise intolerance O2 (6-10%): nausea, prostration, coma O2 (<6%): rapid loss of consciousness

Simple AsphyxiantsSimple Asphyxiants

Treatment

Immediate removal from exposure

Supportive measures (esp. supplemental

O2)

Toxic AsphyxiantsToxic AsphyxiantsInhalation of asphyxiants which have toxicity to tissues

Carbon monoxide (CO)

Hydrogen cyanide (HCN)

Hydrogen sulfide (H2S)

COCO An odorless, colorless gas CO intoxication: the leading cause of

death from gas inhalation Exposure:

Incomplete combustion of fuels (vehicles, forklifts, generators, … esp. when used indoors)

Jobs: Firefighters, petroleum refinery workers,

furnace operators, …

COCO Mechanism of action:

Binding to Hgb (COHb):

↓ O2 binding capacity

Leftward shift of O2 dissociation curve

Binding to cytochrome oxidase:

Compromising cellular respiration Clinical findings:

Headache, nausea, vomiting, malaise, loss of consciousness, coma, death, cardiac ischemia

Lab data: ↑ COHb in cooximetry Routine ABG is not helpful EKG (MI without typical chest pain)

COCOTreatment

Immediate removal from exposure

100% O2

Hyperbaric oxygen

HCNA colorless gas with bitter almond odorUses:

metal plating, and extraction of silver and gold salts from ores

Exposure: thermolysis byproduct of many polymers

Jobs: Pesticide workers, printing, soldering,

firefighting, photography, paper production,… Mechanism of action:

Binding to cytochrome oxidaseClinical findings:

Dyspnea, dizziness, headache, confusion, loss of consciousness, coma, death

HCN

Lab findings: Blood cyanide level (not available) Urine thiocyanate (not reliable)

Treatment: Removal of exposure Induction of metHgb (300 mg Na nitrite) Detoxification of cyanide (sodium

thiosulfate) Supportive measures

H2SA colorless gas with rotten egg odorExposure:Many jobs (petroleum production and refinery, farming, chemical laboratory, excavators, fish processing, sewage workers,…Mechanism of action:

Binding to cytochrome oxidase Irritant effect on mucous membranes

H2S Clinical findings:

Irritant findings: airway irritation, burning eyes

Headache, dizziness, nausea and vomiting

Dermatitis, pneumonitis, pulmonary edema

loss of consciousness, coma, death Lab data:

Blood sulfide level Treatment:

Removal of exposure

Induction of metHgb (300 mg Na nitrite)

Supportive measures