Diagnostic Accuracy of Capnography in Nasogastric Tube Placement

Diagnostic Accuracy of Using Capnography in Verification of Nasogastric Tube Placement in Hospital Settings

A prospective observational diagnostic study will be conducted to assess the sensitivity and specificity of using capnography in detecting the correct placement of nasogastric tubes using the reference standards of radiography and measurement of aspirates for pH value.

A prospective observational diagnostic study will be conducted. Patients ≥ 18-year-old and requiring the insertion of an nasogastric tube will be recruited using a convenience sampling method from general medical and geriatric wards, intensive care units (ICUs), accident and emergency departments (AEDs), and subacute/rehabilitation/infirmary wards in 21 acute or subacute/convalescent/extended care hospitals. End-tidal carbon dioxide (ETCO2) detection by sidestream capnography, which indicates airway intubation of an nasogastric tube when a capnogram waveform or an ETCO2 level > 10 mmHg, will serve as the index test. The reference standards will be the pH value of gastric content aspiration (pH ≤ 5.5 indicates gastric placement) and X-ray performed after the index test. Each participant will be included only once. Sensitivity, specificity, positive predictive value, and negative predictive value, and the area under the receiver operating characteristic curve of capnography will be calculated to assess the diagnostic performance of capnography. The variability in diagnostic accuracy in participants with different characteristics will be compared. The time spent and the cost of the index test and the reference test will be compared.

This study will provide evidence on the diagnostic accuracy of capnography in verifying nasogastric tube placement and inform the update of clinical practice guidelines and stakeholders' decisions regarding the adoption of ETCO2 detection as a routine method for verifying nasogastric tube placement.

Inclusion Criteria:

• 18 years old or above;
• Admitted to the general medical and geriatric wards, ICUs, or subacute/rehabilitation/infirmary wards in subacute/convalescent/extended care hospitals or visiting AEDs in acute hospitals;
• Requiring the insertion of an nasogastric tube into the stomach for assessment, nutritional support and medication administration during the study period.

Exclusion Criteria:

• Participants receiving life-saving intervention at the time of recruitment.