Ultrasonography Versus Capnography in Detecting Endotracheal Tube Placement During Intubation in a Tertiary Hospital.

Overview

After endotracheal intubation verifying the location of endotracheal tube is of utmost importance. Many methods have been applied but none is perfect. The standard practice in the investigator's center has been to use auscultation of chest with capnography. Ultrasound machines are now gaining popularity and their access extends from operation theatres, emergency rooms and even many primary health centres. Both capnography and ultrasonography are safe. This study found out that Ultrasonography and waveform capnography are both reliable methods of confirming endotracheal tube position. The use of ultrasound could help reduce time and increase precision of confirming endotracheal tube position. Ultrasound can confirm endotracheal tube position before manual bag ventilations, and thus may prevent aspiration of gastric contents into patient's lungs.

This was a prospective, observational study conducted at the Tribhuvan University Teaching Hospital (TUTH) and Manmohan Cardiothoracic Vascular and Transplant Center (MCVTC) operating rooms from January 2017 to July 2017. Ethical approval from the Institutional Review Board (IRB) of Institute of Medicine (IOM) and the Department of Anaesthesiology, Maharajgunj Medical College (MMC) was taken. Written informed consent was taken. ASA I and II patients over 16 years of age were included in this study. Patients with difficult airway and anticipated difficult intubation, respiratory diseases, poor functional status, emergency case, and patients at risk of aspiration were excluded. The diagnostic characteristics of real-time, suprasternal, transtracheal ultrasonography and capnography were tested by calculating their respective sensitivities, specificities, positive predictive values (PPV), negative predictive values (NPV), accuracies and likelihood ratios. Comparison of time taken for confirmation of endotracheal tube position from the beginning of laryngoscopy, by ultrasonography versus capnography was done using t-statistics. The degree of agreement of result between ultrasonography and capnography was tested with kappa statistics. Out of the 95 patients studied, 11 had oesophageal intubation (Incidence of 11.57%). The overall accuracy of both ultrasonography and capnography was 96.84%. The sensitivity, specificity, PPV, NPV with their corresponding 95% confidence intervals (CI) for ultrasonography were 97.62% (91.66% - 99.71%), 90.91% (58.72% - 99.77%), 98.80% (92.67% - 99.81%), 83.33% (55.66% - 95.22%) respectively; and that for capnography were 96.43% (89.92% - 99.26%), 100% (71.51% - 100%), 100% (100% - 100%) and 78.57% (54.69% - 91.76%) respectively. The likelihood ratio of a positive and a negative result for ultrasonography were 10.74 and 0.03 respectively, and that for capnography were infinity and 0.04 respectively. The kappa value was 0.749 (95% CI: 0.567 - 0.931) which meant a good degree of agreement of result between these two methods. The average time taken for confirmation of endotracheal tube by ultrasonography and capnography were 26.79 ± 7.64 seconds and 43.03 ± 8.71 seconds (mean ± standard deviation) respectively. The median time for confirmation was 26 seconds with interquartile range \[15 - 37\] seconds for ultrasonography and 42 seconds with interquartile range \[29 - 55\] seconds for capnography. Ultrasonography was found to be faster than capnography by 16.36 ± 3.23 seconds (mean ± standard deviation) and the difference in time was significant (p = 0.011). During the study, one patient had unanticipated difficult intubation, and four had hypotension after induction of anaesthesia. These patients were excluded from the study and no sequalae of hypotension was seen in the patients, or no hypoxemia occured in the patient with unanticipated difficult intubation.