Carbon dioxide detection for diagnosis of inadvertent respiratory tract placement of enterogastric tubes in children.

BACKGROUND

The insertion of an enterogastric tube (oral or nasal) (EGT) is the passage of a tube through the nose or mouth into the stomach. In a paediatric setting, EGTs are used within clinical practice for a variety of reasons including enteral feeding, decompression, post-gastrointestinal surgery, patient assessment, and drug and fluid administration. Confirmation of EGT placement is required immediately following insertion and thereafter prior to each use, including after the administration of enteral feed or medication. Although the majority of these tubes are inserted and used without incident, there is an established risk that the tube can be misplaced into the lungs or move out of the stomach. This misplacement can result in significant harm or mortality. As such, diagnostic tests are required to assess the placement of EGTs and to rule out the target condition of potential airway placement. Various methods are used to determine EGT position, including bedside assessment and observing for signs of respiratory distress. Air insufflated (blown) through the EGT in combination with epigastric auscultation (listening to the stomach with a stethoscope) for whooshing sounds has also been used. Although these tests are widely recognised, they are not officially recommended for use as standalone measures of EGT placement. Current American and UK guidelines recommend a combination of aspirate testing and radiological confirmation of EGT placement in infant, child, and adult populations. In adults, objective measures of pH of the aspirate may be used, with a pH reading between 1 and 5.5 considered a reliable method for excluding placement in the pulmonary tree. However, testing for acidity of aspirate obtained from the EGT does not accurately differentiate between bronchial and gastric secretions in paediatric practice. Additionally, there may be difficulty in obtaining aspirate from the EGT especially within a paediatric population due to the size of the EGT and the smaller volumes of gastric secretions produced. Radiography or direct visualisation are the only reliable methods of confirming EGT placement (valid at time of X-ray and point of insertion, respectively) in this population and are thus considered the reference standard. However, within the paediatric population, there is a known difficulty with obtaining radiographs that visualise the entire course of the EGT and a recognised risk in radiation exposure in the paediatric setting. The measurement of carbon dioxide (CO₂) in exhaled air is a recognised and mandatory standard of care for confirming and monitoring endotracheal tube or airway placement under general anaesthesia. The measurement of CO₂ can be achieved in one of two ways: capnography or colorimetric capnometry. Capnography is the measurement of inspired and expired CO₂ using the absorption of infrared light by CO₂ molecules to estimate CO₂ concentrations. These measurements are then displayed against time to give a continual graphical trace. Colorimetric capnometry involves the detection of CO₂ using an adapted form of pH filter paper impregnated with a dye that changes colour from purple to yellow in the presence of CO₂; however, this method does not provide a continual reading. The monitoring of CO₂ emanating from an EGT inadvertently passed into the airways would utilise this phenomenon in a reverse manner, confirming tracheobronchial placement rather than the intended stomach.

OBJECTIVES

To determine the diagnostic accuracy of capnometry and capnography for detecting respiratory EGT placement in children compared to the reference standard.

SEARCH METHODS

We searched the Cochrane Register of Diagnostic Test Accuracy Studies, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, CINAHL, and Medion database on 4 September 2023. There were no limits on language or publication status.

SELECTION CRITERIA

We included studies that compared the diagnostic accuracy of CO₂ detection (assessed by either capnometry or capnography) for EGT placement in the respiratory tract with the reference standard, and those that evaluated the diagnostic accuracy of CO₂ detection for differentiating between respiratory and gastrointestinal tube placement, in children. We included both prospective and retrospective cross-sectional studies. We included diagnostic case-control studies where patients acted as their own controls whereby the same EGT and end placement was tested both via index and reference test concurrently.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed methodological quality using QUADAS-2. There were no disagreements. Where data were available, we reported test accuracy as sensitivity and specificity. Calculation of both sensitivity and specificity with a 95% confidence interval (CI) was only possible for one study. We calculated specificity with a 95% CI for all included studies. Due to the low number of included studies, we were not able to perform meta-analysis or conduct our planned investigations of heterogeneity.

MAIN RESULTS

We identified three studies for inclusion in the review, all of which provided data on test accuracy of capnography or capnometry against the radiological test standard. Across the three studies, there were a total of 121 participants and 139 EGT insertions with low event data for false-positive (n = 6 insertions) and true-positive (n = 3 insertions) scenarios. No event data were available for false-negative scenarios. Overall, the body of evidence has a low risk of bias, although further clarity regarding patient enrolment (whether consecutive or random) and details about the conduct of the index and reference tests would have enhanced the overall quality of the evidence base included in the review.

AUTHORS' CONCLUSIONS: There is currently not enough evidence to suggest that CO₂ detection for inadvertent respiratory tract placement of EGTs in children should be added to current checking procedures. Future studies should aim for larger samples across a range of ages and evaluate different types of CO₂ monitoring (capnography and capnometry), using a range of EGT sizes in participants who are both spontaneously breathing or who require mechanical ventilation with or without impairments of conscious level.