Comment questions cost estimates for capnography in nasogastric tube verification

The commentary examines a cost estimate based on a prospective multicentre diagnostic accuracy study of capnography for detecting airway placement of nasogastric tubes in 508 patients at 21 hospitals. In the model discussed, radiography was assigned only to patients with end-tidal carbon dioxide (ETCO₂) above the selected threshold. At a threshold above 5 mmHg, 23 patients tested positive and 485 negative; omitting radiography for those testing negative produced an estimated saving of HK$210.3 per patient versus radiography for all. The original authors described this comparison as hypothetical, not a cost-effectiveness analysis.

The commentators note that aspirate was unavailable in 241 patients and pH exceeded 5.5 in another 61. Given the reported marginal counts, at least 279 capnography-negative patients had unavailable aspirate or pH above 5.5, though the exact overlap is unknown. They argue that savings should be recalculated for a defined combined pathway, including any further bedside checks, imaging and tube repositioning. They also call for comparison with locally used verification pathways and clarification of how a negative capnography result would support tube use, particularly in care-home patients. The commentary reports no new data; its cost illustration is limited by the absence of joint results for the verification steps.