A 4-year-old with sudden drooling, stridor, and a suspected swallowed coin arrives after hours, is stable for radiography, and the physician requests neck and chest localization before endoscopy. Which soft tissue neck and foreign body protocol best demonstrates an ingested versus aspirated object?

The correct protocol is right because AP and lateral soft tissue neck places the opacity relative to the anterior tracheal air column versus posterior esophagus and shows retropharyngeal soft-tissue swelling, while frontal inspiratory-expiratory chest adds coin orientation with esophageal coins coronally en face versus tracheal coins sagittally edge-on plus detection of check-valve air trapping, mediastinal shift, or atelectasis from a coexistent radiolucent aspiration that explains stridor with drooling in a stable 4-year-old before endoscopy. The inspiratory-only neck-plus-chest approach fails on physiology because it localizes an opaque coin but cannot show expiratory air retention or asymmetric emptying that proves airway involvement. The frontal-neck-only approach with paired chest phases fails on anatomy because it preserves lung dynamics but loses the lateral plane needed to separate cricopharyngeal esophageal impaction from intratracheal position. The lateral-chest-only approach fails on projection because it keeps neck anatomy and respiratory phases yet omits frontal volume comparison and en face versus edge-on assessment critical for ingestion versus aspiration triage. Exam caveat is that drooling with stridor signals threatened airway, so do not delay endoscopy or anesthesia backup, avoid oral contrast and agitation, and monitor continuously after hours. Practical check is true lateral neck in extension on inspiration from nasopharynx to inlet, matched inspiratory-expiratory frontal chest with markers, and survey whole tract for second coin.