The current standard for verifying endotracheal tube placement includes visualizing the tube passing through the vocal chords, seeing fogging of the tube, bilateral chest raise and then ausculation over the epigastrium and bilaterally over the lungs. The latest addition has been the capnograph, which has quickly established itself as a standard. But could there be another way?
Capnography, with a constant, continuous waveform is the gold standard for tube placement verification. It is also a great tool for monitoring the patient and the patient’s ventilation. The downside is that it takes a little while to set up, connect and then confirm tube placement. Especially since you really need to see a few waves to make sure the CO2 is not quickly diminishing as a sign of esophageal intubation.
Auscultation is quick, but not always that reliable and it has limitations in noisy environments, like the pre-hospital setting.
This study looks at another way of confirming tube placement. Ultrasound.
With Ultrasound you can try to visualize the passing of the tube through the esophagus, either through the window of the cricoid membrane, or through the trachea. Ultrasound is also well established for visualizing lung ventilation through different signs of lung sliding, or actually pleura sliding. Mostly used for ruling out pneumothorax. But in this study, it’s used for verifying lung ventilation.
Ultrasound vs stethoscope and capnography
The study’s main goal was to study the time it took to verify ETT placement. US vs. auscultation was equal regarding time (and, I guess, provided you have the ultrasound machine next to you and ready to go). With US vs. auscultation and capnography, US was quicker. It is not clear from the study, but I assume both the US-machine and the capnography set-up was ready to go.
I like how the US operator in this study only had limited US experience. Only 3 hours of training before the study commenced.
Some weaknesses. The study does not take into account that US and capnography needs time to set up and start. Stethoscopes are ubiquitous. Also, it does not tell the time to verify misplaced tubes, as all intubations were successful in this study. But for normal patients, I would assume similar times for verifying misplacement. For sick patients with severe lung pathology, it might be more difficult to verify with US. Passing the tube down the trachea was only verified with US in 68% of the cases, so it’s hard to use as an intubation tool.
The bottom line is that it’s nice to have yet another tool to reach for if your standard tools should fail. It is also great to use US instead of a stethoscope in noisy environments. The US will often be there for line placement, a FAST or pneumothorax scan, so use it to confirm tube placement and ventilation as well.
Temporal comparison of ultrasound vs. auscultation and capnography in verification of endotracheal tube placement. P. Pfeiffer, S. S. Rudolph2, J. Børglum and D. L. Isbye
Akutcentrum/Anestesikliniken, Skåne University Hospital, SUS Malmø, Sweden and Department of Anaesthesia and Intensive Care Medicine, Copenhagen University Hospital, Bispebjerg, Denmark.
A new study on the same subject, but looking at obese patients, came to the same conclusion:
Verification of endotracheal intubation in obese patients – temporal comparison of ultrasound vs. auscultation and capnography, Acta Anaesthesiol Scand, 2012.