Etiology
- Silo Filler’s Disease
- Farmer inhalational exposure to decomposing organic matter in silo (usually occurs within 2 weeks after filling silo)
- Nitrogen dioxide gas is released from decomposition of organic matter
- Internal Combustion Engine: inhalational exposure in enclosed space (example: ice resurfacing in indoor skating rinks)
- Explosion or Fire: thermal degradation of polymers -> inhalational exposure
- Industrial Exposure: release of compressed nitrogen dioxide gas
- Gas-Shielded Welding: manual inert gas or tungsten inert welding -> inhalational exposure
- Detonation of Explosives: inhalational exposure
- Inhaled Nitric Oxide (NO) Therapy (see Nitric Oxide, [[Nitric Oxide]]): in presence of oxygen, NO breaks down into nitrogen dioxide
- Requires monitoring of NO2 levels during NO therapy
- Nitric Acid Treatment of Wood: releases nitrogen dioxide
Physiology
- Nitrogen Dioxide Gas Inhalation: nitrogen dioxide gas has a distinctive red-brown color and is heavy
- Highest concentrations occur just above the silage (in the case of silo-related exposures)
- Low Water Solubility: may result in longer exposure and delayed injury to bronchioles and alveoli before the vicitim becomes aware of the exposure
- Nitrogen Dioxide Gas Increases Airway Epithelial Permeability: may allow direct stimulation of airway smooth muscle or stimulate parasympathetics (with resulting bronchoconstriction)
Diagnosis
- FOB: necessary to rule out airway injury
- CXR/Chest CT Patterns (depends on degree of exposure)
- Normal CXR: some cases
- Normal CXR does not rule out significant injury or possibility of later developing symptoms
- Diffuse Nodular Infiltrates: some cases
- Pulmonary Edema: some cases with severe exposure
- Normal CXR: some cases
Clinical Presentations
(delayed onset of pulmonary injury -> symptoms may occur hours-days later in some cases)
- Silo Filler’s Disease
- Clinical
- Minimal upper airway injury and conjunctival irritation
- Dyspnea
- Choking sensation
- Cough with frothy or mucoid sputum
- Diagnosis
- CXR/Chest CT
- Normal CXR: normal CXR does not rule out significant injury or possibility of later developing symptoms
- Diffuse Micronodular/Nodular Infiltrates (see Lung Nodule or Mass, [[Lung Nodule or Mass]]): may be seen in subacute exposure
- Diffuse Infiltrates (see Pneumonia, [[Pneumonia]]): may be seen with acute exposure
- CXR/Chest CT
- Clinical
- Acute Lung Injury-ARDS (see Acute Lung Injury-ARDS, [[Acute Lung Injury-ARDS]])
- Epidemiology: with high-level exposure
- Pathology: diffuse alveolar damage
- Clinical: may be rapid in onset
- Bronchiolitis Obliterans (see Bronchiolitis Obliterans, [[Bronchiolitis Obliterans]])
- Epidemiology: occurs in only 1 in 20 cases with moderate-severe exposure
- Cryptogenic Organizing Pneumonia (see Cryptogenic Organizing Pneumonia, [[Cryptogenic Organizing Pneumonia]])
- Reactive Airway Dysfunction Syndrome (see Reactive Airway Dysfunction Syndrome, [[Reactive Airway Dysfunction Syndrome]])
- Epidemiology: may be seen in some cases
- Pulmonary Alveolar Proteinosis (see Pulmonary Alveolar Proteinosis, [[Pulmonary Alveolar Proteinosis]])
Treatment
- Avoid Exposure: do not enter silo until >2 weeks after filling
- Steroids: may be benficial in acute lung injury, but unproven
References
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