Colourimetric capnometry to verify nasogastric tube placement in patients at risk of mal-placement

Background. Nasogastric tubes (NGT) are frequently used in geriatric settings and verification of NGT placement is important for patient safety. This study aimed to ascertain the accuracy of carbon dioxide (CO2) colourimeter in the verification of NGT and to estimate the reduction in patient waiting time for resumption of NGT feeding in the general care setting. Methods. Doubtful NGT placements were obtained from patients in three medical extended wards in a public hospital in Hong Kong. Doubtful NGT placements were verified using both X-ray imaging and CO2 colourimeter. The sensitivity and specificity of CO2 colourimeter were evaluated using X-ray imaging as the gold standard. The patient waiting time for resumption of NGT feeding were estimated by recording the time required for completion of X-ray imaging verification. Results. There were 26 patients in the study with a mean age of 74.07 years (SD = 16.33). Fifteen (57.7%) of them were male. The final sample consisted of 71 doubtful NGT placement and none of them was misplaced. The specificity of CO2 colourimeter was 98.6%, while the sensitivity was unable to determine. The patient waiting time required for X-ray imaging verification ranged from 51 to 1095 minutes (mean = 380.75 min., SD = 179.51). Conclusions. CO2 colourimeter has high specificity in verification of doubtful NGT placement. Replacing X-ray imaging with CO2 colourimetry verification may speed up resumption of NGT feeding.