Polyvinyl chloride
The "armored" endotracheal tubes are cuffed, wire-reinforced, silicone rubber tubes that are quite flexible but yet difficult to compress or kink. This can make them useful for situations in which the trachea is anticipated to remain intubated for a prolonged duration, or if the neck is to remain flexed during surgery. Polyvinyl chloride tubes are relatively stiff in comparison. Preformed tubes (such as the oral and nasal RAE tubes, named after the inventors Ring, Adair and Elwyn) are also widely available for special applications. These may also be constructed of polyvinyl chloride or wire-reinforced silicone rubber. Other tubes (such as the Bivona Fome-Cuf tube) are designed specifically for use in laser surgery in and around the airway. Various types of double-lumen endotracheal (actually, endobronchial) tubes have been developed (Carlens, White, Robertshaw, etc.) for ventilating each lung independently—this is useful during pulmonary and other thoracic operations.