Final answer:
The next critical step after placing a nasogastric tube for tube feeding in a patient who has failed a swallow study is to obtain a chest radiograph.
Step-by-step explanation:
The next critical step after placing a nasogastric tube for tube feeding in a patient who has failed a swallow study is to obtain a chest radiograph. This is important to confirm the proper placement of the tube in the stomach and to ensure that there is no accidental placement in the lungs or airway.