Tracheal wash
A 120 cm long videoendoscope (AOHUA, Medimage off-site; OLYMPUS in-house) was passed through one of the nostrils into the pharynx. The endoscope was then inserted into the proximal trachea, and the presence of blood in the trachea and the mainstem bronchi was graded from 0 to 4 based on a reported scoring system (tracheal blood score, TBS).13 Tracheal mucus was also scored according to a previously published scale from 0 to 5.14 A single-use double-lumen sterile catheter (Mila International Inc.) was passed through the canal of the endoscope, and 40 mL of warmed (37°C) sterile saline solution (0.9% NaCl) was infused and retrieved. The aspirated fluid was divided between a sterile dry tube for microbiology (bacteriology and mycology), and a tube containing EDTA for cytological analysis.