Smoke Inhalation

Smoke Inhalation



Basic Information image



Definition


Injury caused by exposure to a fire with a great deal of smoke, especially a fire in a confined area such as a barn or arena. Horses are at risk for carbon monoxide poisoning, chemical insult, and direct thermal injury to the respiratory system. The most severe consequence is pulmonary edema and death caused by asphyxia.



Synonym(s)




• Carbon monoxide poisoning


• Lung thermal injury


• Lung chemical injury



Epidemiology



Species, Age, Sex




• Barn fires are one of the most common causes of burns and smoke inhalation in horses of any age.


• Horses housed in at-risk barns (no fire detection or protection systems) are at increased risk for smoke inhalation if a fire occurs.



Clinical Presentation



Disease Forms/Subtypes


Inhalation injury is a common sequela of closed-space fires and develops through three mechanisms



• Direct thermal injury


• Carbon monoxide poisoning


• Chemical insult



History, Chief Complaint




• History of smoke inhalation related to a barn fire


• Commonly an associated burn injury to the skin of various depth and extent (see “Burns” in this section)



Physical Exam Findings




• Tachypnea


• Tachycardia


• Pale, blue, or toxic mucous membranes; cool extremities; poor peripheral pulses



Etiology and Pathophysiology




• Direct thermal injury causes edema and obstruction of the upper airway.


• Carbon monoxide interferes with oxygen delivery in several ways because its affinity for hemoglobin is approximately 230 times the affinity between oxygen and hemoglobin (shifts the oxygen-hemoglobin curve to the left).


image The resultant carboxyhemoglobin is incapable of oxygen transport.

image Carbon monoxide also binds to myoglobin, impairing oxygen transport to muscles.

image Carbon monoxide is excreted by the lungs at a rate relative to ambient oxygen tensions. In room air, carbon monoxide has a half-life of more than 3 hours.

image An increase in oxygen tension promotes the dissociation of carbon monoxide and hemoglobin; thus, 100% oxygen therapy reduces the half-life to 30 to 40 minutes. Hyperbaric oxygen therapy at 2.5 atm further decreases the half-life to 22 minutes.

• Chemical insult depends on the material that was burned.


image Combustion products such as hydrogen cyanide, hydrochloric acid, phosgene, sulfuric acid, and aldehydes may induce severe tracheobronchitis when combined with the moisture in the airways.

image Initially, only erythema may be present, but chemical injury continues as long as chemical-covered carbon particles remain attached to the airway mucosa. Particle size determines where damage will occur within the respiratory tree.
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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Smoke Inhalation

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