The dark and patchy coloration that becomes confluent in all the trachea closest to this image, is due to the presence of abundant accumulated carbon particles and combined with mucus.
They were inhaled during a fire and may exist with or without airway burn.
The endoscopic examination is “poorly lit”; this effect is a consequence of the absorption of light by the dark material that covers the mucosa.
A similar phenomenon occurs in exploratory endoscopy of copious hemoptysis in which the blood absorbs much of the illumination provided by the endoscope.
Particles phagocytized by macrophages can be seen in the sputum examination.
Francisco Muñiz Hospital