Fig. 4. Confocal scanning micrograph of the internal surface of a standard endotracheal tube and coated endotracheal tube after 24 h of mechanical ventilation. Confocal scanning micrograph of coated endotracheal tube (a ) and uncoated endotracheal tube (b ) showing layering of interfaces. Note great increase in biofilm thickness in b  compared with thin proteinaceous layer in a . Between arrows , silver sulfadiazine-chlorhexidine in polyurethane. Bar  (bottom right ), 40 μm.