Has Video Finally Killed DL?
/Prekker, M. E. et al. Video versus Direct Laryngoscopy for Tracheal Intubation of Critically Ill Adults. N. Engl. J. Med.389, 418–429 (2023).
Clinical Question: Does video laryngoscopy increase the likelihood of first attempt tracheal intubation with compared to direct laryngoscopy?
Background
More than 1.5 million adults undergo tracheal intubation outside of the operating room each year in the United States. Traditionally, this has been performed with direct laryngoscopy, where a clinician displaces the patient’s tongue and epiglottis with a laryngoscope blade to visualize the vocal cords through the mouth, allowing for direct visualization of the passage of an endotracheal tube. An alternative method for tracheal intubation is video laryngoscopy, where a camera on the distal half of the blade transmits an image to a screen allowing for indirect visualization of the vocal cords and passage of an endotracheal tube without direct line of site. While globally, the majority of intubations in the ICU and ED are performed with a direct laryngoscope, the use of video laryngoscopes has increased over time. Several single-center and moderately-sized studies have compared the outcomes of these two methods with varying results. Due to potential harm associated with delayed passage of an endotracheal tube, the incidence of first attempt successful tracheal intubation between either method is of meaningful clinical significance.
Study Design
This was a pragmatic, multicenter, unblinded, randomized, parallel-group trial comparing the use of video laryngoscopy with direct laryngoscopy.
Exclusion Criteria
Patients excluded from the study include those who:
Were under the age of 18 years old
Were known to be pregnant
Were known to be incarcerated or involuntarily detained
Had an immediate need for tracheal intubation that precluded randomization
The clinician performing the intubation determined that one method was either necessary or contraindicated
Methods & Definitions
In total, there were 7 emergency departments and 10 intensive care units across the United States involved in the study. Patients were randomly assigned in a 1:1 ratio to undergo intubation with video or direct laryngoscopy, with trial-group assignments being placed in sequentially numbered opaque envelopes that remained concealed until after enrollment. The protocol dictated the method of first intubation attempt, either video or direct laryngoscopy, but the brand of equipment, blade size, and all other aspects of the procedure itself were at the discretion of the treating clinicians. The study did not dictate the method of subsequent attempts. At all trial sites, a stylet or bougie was routinely used during first attempt tracheal intubation, and waveform capnography or colorimetric end-tidal carbon dioxide detection was used to confirm tube placement. Data surrounding the intubation, including number of attempts, duration of intubation, and lowest oxygen saturation and systolic blood pressure, was collected by a trained observer not involved in the performance of the intubation. The operator reported a subjective assessment of the anticipated difficulty. Immediately following intubation, they also reported the Cormack-Lehane grade of glottic view obtained, reasons for failure of intubation on first attempt, procedural complications, and the number of previous intubations they had performed. Trial personnel reviewed the medical record to collect each patient's baseline characteristics, periprocedural care, and clinical outcomes.
Primary outcome: successful intubation on first attempt
Successful intubation on first attempt was defined as placement of the endotracheal tube in the trachea with a single insertion of the laryngoscope and either one insertion of the endotracheal tube or insertion of a bougie followed by a single insertion of an endotracheal tube.
Secondary outcome: occurrence of severe complications between induction and 2 minutes after intubation
Severe complication was defined as severe hypoxemia (oxygen saturation <80%), severe hypotension (systolic blood pressure <65 mmHg), new or increased use of vasopressors, cardiac arrest, or death.
Results
The trial ran from March 19th to November 17th, 2022, and was stopped early after a prespecified interim analysis of the first 1000 patients showed a significant difference between first attempt intubation success between the two groups. Due to continued enrollment while the interim analysis was being performed, the primary analysis was completed with a total of 1417 patients of the 1947 who were assessed for eligibility. Baseline patient characteristics were similar between groups, with a median age of 55 years and about 65% male. BMI was around 26.5 for both groups.
The most common indications for intubation were altered mental status, at 45.3%, and respiratory failure, at 30.4%. Most intubations (69.7%) were performed in the emergency department, with the remainder occurring in an intensive care unit. Both indication and location were close to equivalent between groups. The majority of intubations were performed by trainees, with 91.5% of operators being either emergency medicine residents or critical care fellows. Clinicians performing the intubation had a median of 50 prior intubations.
In the video-laryngoscope group, 600 out of 705 patients (85.1%) had first attempt intubation success. In the direct-laryngoscope group, 504 out of 712 patients (70.8%) had successful first attempt intubation. This was a statistically significant difference with an absolute risk reduction of 14.3% associated with the use of video laryngoscopy, and a number needed to treat of only 6.9. There was no statistically significant difference between severe complications during or immediately following intubation. Safety outcomes including esophageal intubation, injury to teeth, and aspiration were each also similar between the two groups.
Sensitivity analyses were performed looking at trial site, missing data, and only including patients in whom the operator had performed a similar percentage of previous intubations with video laryngoscope (25-75%) did not result in significant change in outcome.
Takeaway
This was a large study looking at an important clinical question performed in a pragmatic design that closely matches what we see every day in the emergency department. There were broad inclusion criteria though about 25% of patients meeting the study criteria were excluded. The majority, about half of the excluded patients, were due to emergent need for intubation precluding randomization, though another large cohort were patients where video laryngoscope was felt to be required, primarily due to difficult anatomy. While this suggests the possibility of selection bias in the results, this would be expected to bias against video laryngoscopy as operators were selecting this method for the anticipated most difficult intubations.
Interpreting the importance of this study largely comes down to how you view the primary outcome of first past success. While this is an intuitive measure, and we would expect it to influence a patient’s care, it is not a directly patient-oriented outcome. While there was a statistically significant difference in first-pass success between the two methods, there was no statistical difference among the secondary outcomes. This may be due to the relatively stringent criteria for "severe complication" detailed above, and in some cases desaturation or hypotension not meeting the strict prespecified levels could still be expected to have clinical significance. However, even without statistical differences in these secondary outcomes, it is hard to argue that our patients are not best served by intubation on the first attempt.
The study had 387 unique operators with varying degrees of experience including total number of intubations and prior exposure to video or direct laryngoscopy. At all levels of experience, video laryngoscopy resulted in a higher likelihood of first pass success, although this difference narrowed and lost statistical significance as the number of previous intubations increased. For operators with less than 25 previous intubations, the absolute difference in first pass success was 26.1%, but this decreased to just 5.9% in operators with more than 100 prior intubations. This difference in success among operators with different levels of experience has important implications for academic settings in particular.
Certainly, use of video laryngoscope seems to result in increased first pass success and should be prioritized for airways with anticipated difficulty. However, there remains a role for direct laryngoscopy and competency with this method remains an important aspect of clinical training. The use of specialized blades that allow for both direct and video laryngoscopy seems like an appropriate compromise. Typically, these blades are constructed with similar shape and size to traditional direct laryngoscopes, though with a camera mounted part way down the blade, as in video laryngoscopes. This allows operators to initially attempt direct laryngoscopy, with the option for quickly transitioning to video laryngoscopy without removing the blade, by simply looking at the camera view on an attached screen. Based on the results described above, this is likely the ideal way to both maintain direct laryngoscopy skills and still provide the safest care for patients.
Additional details from the results of this study include the difference in time to successful first pass intubation. Figure 1 shows the cumulative incidence of first pass success based on time, with the split between video and direct laryngoscopy occurring around the 20 second mark and continuing to widen until about 60 seconds at which point neither method has any meaningful change in incidence. While not a studied outcome of the paper, this would suggest that an intubation attempt lasting longer than 60 seconds has low likelihood of resulting in a successful intubation, and alternative strategies including a change in positioning, blade, or operator should be considered.
Overall, this was a large study looking at an important clinical question performed with a pragmatic design that closely matches what we see every day in the emergency department. They found that video laryngoscopy resulted in a higher incidence of first past success for tracheal intubation when compared with direct laryngoscopy. This effect size was greater when fewer previous intubations had been performed by the operator. While secondary outcomes between the two methods were not statistically significant, if you accept that first pass success carries clinical significance then this is a strong argument in favor of video over direct laryngoscopy in a general ED and ICU patient population requiring intubation.
Authorship
Written by - Thomas Haffner, MD, PGY-3 University of Cincinnati Department of Emergency Medicine
Audio recording and Editing - Saie Joshi, MD PGY-2, University of Cincinnati Department of Emergency Medicine
Peer Review - Andrew Adan, MD, Assistant Professor, University of Cincinnati Department of Emergency Medicine
Editing and Posting - Jeffery Hill, MD MEd, Associate Professor, University of Cincinnati Department of Emergency Medicine
Cite As
Haffner, T. Joshi, S, Hill, J., Adan, A. Has Video Finally Killed DL? www.tamingthesru.com/blog/journal-club/has-video-killed-dl. TamingtheSRU. 9/22/23
