Date: March 12th, 2019

Reference: Gottlieb, Holladay and Peksa. Ultrasonography for the Confirmation of Endotracheal Tube Intubation: A Systematic Review and Meta-Analysis. Ann Emerg Med 2018.

Guest Skeptic: Chip Lange is an Emergency Medicine Physician Assistant (PA) working primarily in rural Missouri in community hospitals. He hosts a great #FOAMed blog and podcast called TOTAL EM. Chip is also the CEO of a new educational company called Practical POCUS.

Case: A 48-year-old male is in cardiac arrest and is not being successfully oxygenated by bag valve mask or with a supraglottic airway (SGEM#246).  While preparing to intubate the patient, you consider ways of quickly confirming endotracheal tube placement.  You have a colleague in the room who is proficient at ultrasound and asks if there is a role for bedside ultrasound in this situation.

Background: We have talked about ultrasound a number of times on the SGEM:

  • SGEM#245: Flash-errrs (POCUS for Retinal Detachments)
  • SGEM#177: POCUS – A New Sensation for Diagnosing Pediatric Fractures
  • SGEM#153: Simulation for Ultrasound Education
  • SGEM#124: Ultrasound for Skull Fractures – Little Bones
  • SGEM#119: B-Lines (Diagnosing Acute Heart Failure with Ultrasound)

The SGEM has also discussed endotracheal intubation a number of times:

  • SGEM#247: Supraglottic Airways Gonna Save you for an OHCA?
  • SGEM#197: Die Trying – Intubation of In-Hospital Cardiac Arrests
  • SGEM#186: Apneic and the O, O, O2 for Rapid Sequence Intubations
  • SGEM#75: Video Killed Direct Laryngoscopy?

Endotracheal intubation can be challenging and if incorrectly performed can lead to death.  Rapid confirmation of endotracheal tube placement is vital and ACEP has a policy statement on this issue. The various methods to confirm tube placement include:

  • Physical exam (auscultation of chest and epigastrium, chest wall movement, and condensation/fogging in the tube)
  • Direct visualization or videolaryngoscope of the tube going through the cords
  • Pulse oximetry
  • Chest x-ray
  • Esophageal detector devices
  • End-tidal carbon dioxide (CO2) detection (continuous wave form capnography, colorimetric and non-wave form capnography)

There is evidence indicating that commonly used endpoints for rapid confirmation can be inaccurate.  Quantitative waveform capnography, thought to be one of the best methods, correctly confirms tube placement only two-thirds of the time.

A fast and reliable alternative would be great.  Point of care ultrasound (POCUS), has become more popular over time for its easy usability and accuracy in a variety of applications.  A number of small studies have been done using POCUS to confirm endotracheal tube placement. These studies have been relatively small with wide confidence intervals.

Clinical Question: What is the accuracy of ultrasonography for confirmation of endotracheal tube placement?

Reference: Gottlieb, Holladay and Peksa. Ultrasonography for the Confirmation of Endotracheal Tube Intubation: A Systematic Review and Meta-Analysis. Ann Emerg Med 2018.

  • Population: Patients over 18 years of age in a prospective or randomized controlled trial undergoing assessment of transtracheal ultrasonography for endotracheal tube placement confirmation.
    • Excluded: Case reports, case series, retrospective studies, cadaver studies, pediatric studies, and conference abstracts.
  • Intervention: Transtracheal ultrasonography to confirm endotracheal tube placement.
  • Comparison: Confirmatory testing of endotracheal tube placement such as end-tidal capnography, colorimetric capnography, or direct visualization.
  • Outcome:
    • Primary Outcome: Diagnostic accuracy of transtracheal ultrasound
    • Secondary Outcome: Time to confirmation and subgroup analyses.

Authors’ Conclusions: Transtracheal sonography is rapid to perform, with an acceptable degree of sensitivity and specificity for the confirmation of endotracheal intubation.  Ultrasonography is a valuable adjunct and should be considered when quantitative capnography is unavailable or unreliable.

Quality Checklist for Systematic Review Diagnostic Studies:

  1. The diagnostic question is clinically relevant with an established criterion standard.  Unsure
  2. The search for studies was detailed and exhaustive.  Yes
  3. The methodological quality of primary studies was assessed for common forms of diagnostic research bias. Yes
  4. The assessment of studies was reproducible. Unsure
  5. There was low heterogeneity for estimates of sensitivity or specificity.  Yes
  6. The summary diagnostic accuracy is sufficiently precise to improve upon existing clinical decision-making models.  Unsure

Key Results: Their search identified 17 studies (15 prospective observational studies and two randomized controlled trials) with 1,595 patients.  Twelve of the 17 studies were done in the emergency department. The mean age was 55 years with 57% being male patients. Esophageal intubation rate was 15%.

Transtracheal ultrasonography was 98.7% sensitive and 97.1% specific.

  • Primary Outcome: Diagnostic accuracy of transtracheal ultrasound for endotracheal tube placement.

  • Secondary Outcome: Mean time to confirmation was 13.0 seconds (95% CI: 12.0 to 14.0)
  • Subgroup Analyses: These did not demonstrate a significant difference by location, provider specialty, provider experience, transducer type, or technique.

1. Included Studies: As stated in the background material, a number of studies have been done using POCUS to confirm endotracheal tube placement. These studies have been relatively small with wide confidence intervals. Most of the studies included in this SRMA were at low risk of bias. However, 15 out of the 17 of the included studies were prospective observational studies. Only 216 patients (14%) were in randomized controlled trials. In addition, 13 of the 17 studies did not enrol consecutive patients but used convenience sampling which can introduce selection bias. These limitations of included studies make it hard to make any strong statement on using transtracheal ultrasound for endotracheal tube placement.

2. Lack of Gold Standard: There is no set established criterion standard to confirm endotracheal tube placement. A number of methods are available and often used in combination. Each confirmation modality has their potential benefits and limitations. Chest x-ray takes a long time to confirm, capnography especially in cardiac arrest has low sensitivity, and auscultation can be inaccurate or difficult to detect especially in loud environments.

3. Esophageal Intubation Rate: This was very high at 15%. A previous study has shown the rate in the ED to be only 3%. (Brown et al. Ann Emerg Med 2015). This could be due to the different level of training of those performing the intubations. Studies included medical students, residents and attending physicians.

4. Accurate and Fast: When confirming endotracheal intubation, you want a method that is both accurate and fast. We talked about the potential limitations with sensitivity of waveform capnography.  Ultrasound provides a much more rapid evaluation to confirm which means fewer potential complications like regurgitation of stomach contents or worsening hypoxia do to improper endotracheal tube placement.  Ultrasound confirmed placement in 13 seconds while capnography can take about 60 seconds. It is unsure if this difference in time results in a patient-oriented benefit.

5. Publication Bias: The funnel plot analysis demonstrated evidence of publication bias. The bias would be towards not publishing negative studies. This is a well-known phenomenon in the medical literature. This form of bias would skew the results and make transtracheal ultrasound placement confirmation look better.

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We agree that transtracheal sonography is rapid, seems to have very good diagnostic accuracy and could be a valuable adjunct when quantitative capnography is unavailable or unreliable.

SGEM Bottom Line: Transtracheal sonography represents a potential fast and accurate way to help confirm endotracheal tube placement in conjunction with other methods.

Case Resolution: Your colleague is familiar with the application of POCUS for endotracheal tube placement and agrees to assist you in your intubation attempt.  While you directly visualize the passage of the endotracheal tube through the vocal cords, she is able to see the appropriate findings consistent with successful placement.  Waveform capnography is used in addition and further supports the appropriate placement.  With this successful intubation, the patient’s oxygen saturations improve.

Chip Lange

Clinical Application: POCUS for confirmation of endotracheal tube placement is another example of emergency medicine embracing this new technology. It represents another potential tool that can be used in combination with existing methods to verify correct tube placement. As these bedside devices become pocket size and more affordable, it will be interesting to see how clinicians continue to include POCUS in their practice.

What Do I Tell the Patient? Since the patient is intubated, there really is not much to tell them.  However, you may tell your team that to help rapidly confirm endotracheal intubation you will use transtracheal ultrasound along with other measures such as direct visualization of the tube’s passage through the cords, auscultation, and waveform capnography.

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