Head extension can cause movement of the tube in a cephalad direction, which may result in bronchial decannulation; head flexion can cause movement of the tube in a caudad direction, which may result in an upper lobe obstruction or in both luminas being in a mainstem bronchus (see next section). 262, 263 Finally, the fiberoptic bronchoscope is used whenever during the case there is a question abou