What is the pathophysiology of smoke inhalation caused by oxides of nitrogen?

Updated: Oct 15, 2021
  • Author: Keith A Lafferty, MD; Chief Editor: Joe Alcock, MD, MS  more...
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NOx are components of photochemical smog, usually approximately 0.053 ppm. Nitrogen dioxide exists as a mixture of nitrogen dioxide, a reddish brown gas, and nitrogen tetroxide, a colorless gas. Other forms of nitrogen oxide include nitrous oxide, which is a common anesthetic or (when inhaled without oxygen) asphyxiant, and nitric oxide, which quickly decomposes to nitrogen dioxide in the presence of moisture.

Inhalation of nitric oxide causes the formation of methemoglobin. Inhalation of nitrogen dioxide results in the formation of nitrite, which leads to a fall in blood pressure, production of methemoglobin, and cellular hypoxia. Inhalation of high concentrations causes rapid death without the formation of pulmonary edema.

More severe exposures result in production of yellow frothy fluid in the nasal passages, mouth, and trachea and marked pulmonary edema, which may be fatal. The symptoms following the inhalation of NOx are mostly due to nitrogen dioxide.

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