European Journal of Cardiovascular Medicine

There is always the chance that a intubation performed via direct laryngoscopy (DL) would not work, and it usually takes physicians a lot of practice before they can master the technique. For example, intubation rates might vary from 35 to 65% for beginners in anesthesiology, and it can take 47 to 56 intubations before they achieve a success rate over 90%.1–6

Lighted stylets, intubating laryngeal masks, fiberoptic bronchoscopes, video laryngoscopes, and other alternatives to traditional laryngoscopy have all been reported in recent years with the goal of improving intubation success rates.6 On the other hand, these options aren't always accessible, may be expensive, and require a high level of technical expertise. So, methods that are both cheap and simple to work with are still sought after. In light of this, we investigated the potential benefits of RLGL, a technique detailed in a recent case study.11 In contrast to DL's antegrade illumination, this technique shows the glottis using retrograde transtracheal light transmission from a skin-attached external light source. This method makes locating and identifying the sparkling glottis a breeze.

Recruitment of Patients and Operators

From May 2021 to April 2022, 205 patients hospitalised for surgery under general anaesthesia were recruited for this prospective, randomised, open-label, parallel-arm superiority trial. Table 1 lists the demographics and patient characteristics of these patients. They signed an informed permission form after being briefed on the study's purpose and experimental protocol before they were given anaesthetic. To guarantee that each research group had an equal number of patients, we employed block randomization to assign each patient in a 1:1 ratio.

Subjects needed to meet specific necessities to be considered for incorporation: a Mallampati score among I and II, a thyromental distance of 6 cm or more, a mouth opening of 3 cm or more, a weight record of 30 kg/m2 or less, and no temporomandibular joint problems, dangers of disgorging or pneumonic goal, or other clear intubation obstacles. Standards for rejection incorporated a C and L grade of III not set in stone by proficient anesthesiologists, as well as serious patient circumstances, for example, an obvious drop in pulse or pulse. Twenty administrators were decided indiscriminately to intubate five patients utilizing either RLGL or DL, whether or not they had at any point intubated a patient beforehand. An equivalent number of attendants (five) and clinical understudies (six) filled in as administrators. Understudies took in the hypothetical establishment, signs, and dangers of DL and RLGL before the examination started, as well as aviation route the executives ideas like C and L grades and pack veil relaxing. Before they could dominate the two strategies, they performed intubations on an aviation route the board mentor puppet (Laerdal Clinical, Stavanger, Norway) until they could do three introduces in succession in just 120 seconds.

RLGL

A light-emitting diode torch is placed onto the skin of the caudal edge of the thyroid cartilage (fig. 1A-C), and the operator can adjust and optimise the location of the torch to illuminate the glottis and pharynx through transtracheal light transmission. This is the essence of RLGL. By turning off the front light during standard laryngoscopy, the opening of the glottis may be seen as a bright point on the otherwise dark red pharynx. Also, the vocal cord and arytenoid cartilage, which are structures encircling the glottis, may be made out, if weakly, in figures 1D–E. The last step is to place the endotracheal tube into the trachea after guiding it via the lighted glottis.

Experimental Design and Protocol

Qualified anesthesiologists oversaw every intubation procedure. The medical personnel, who were not informed about the study's purpose, recorded the patients' characteristics before surgery. Patients were allocated to either DL or RLGL based on computer-generated instructions that were sealed in an envelope just before each procedure. No one knew who the patient was or what method would be utilised to intubate them until the procedure began.

To keep up with head solidness, the patients were situated recumbent on a 7-cm-high cushion. A standard electrocardiogram, beat oximetry, and painless manometry of the blood vessel pulse were utilized to screen the patient's condition. Before being put under broad sedation with a few meds, including midazolam (0.08 mg/kg), propofol (2 mg/kg), fentanyl (2 μg/kg), and rocuronium bromide (0.8 mg/kg), the patient was expected to inhale unadulterated oxygen for at least three minutes.

An auxiliary person steady the light source for RLGL. Once the light was turned off, the operator raised the base of the tongue using the Macintosh blade to align the optical axis. Then, they exposed the pharynx until they could see the lit glottis against the faint red backdrop (fig. 4). By carefully guiding the tracheal tube into the trachea using the illuminated glottis as a guide, its cuff was inflated to completion. There was a strict 120-second time constraint for each intubation. It was forbidden for the supervisors to provide guidance or support to the operators.

Fig. 4. The use of RLGL, to examine the larynx. (A) An assistant holds a torch as a Macintosh laryngoscope sits in position with its light off. (B and C) Silhouettes depict the scenario before and after the light is turned on, respectively. From D to G According on what an observer can see in the original photos, C & L grades I–IV. In contrast to the dull light in the surrounding environment, the retrograde transmitted light shines brightly on the glottis and the region cranial to it, making it stand out like a yellow beacon. (D). Class I (D) and II (E) of C & L are partly and completely matched by the glottis. It seems that neither the glottis nor the epiglottis conform to C & L grade IV. Last but not least, the glottis isn't visible, but the yellow light in the backdrop makes it easy to pinpoint. Although the epiglottis is not always visible with RLGL, we have provisionally classified these instances as C & L grade III. Cormack and Lehane grade (C&L) and glottis (g) are abbreviations for the same thing.

The durations of exposure and intubation were recorded using a stopwatch. The assistant began the timer upon opening the patient's mouth, halted it when the operator communicated the clearest view of the glottis, and resumed its operation upon inflation of the tube's cuff. Another definition of exposure time is the amount of time that passes between the opening of the mouth and the optimal glottic exposure. The intubation time was defined as the time it took to insert the tube.

The administrators assessed the glottic openness in light of C and L12 grades (fig. 1D-G). To decide if a work was fruitful, we searched for three things: ( 1) proof of protection from passing the cylinder, (2) endeavors to reexpose the glottis by pulling out the cylinder from the mouth, and (3) side effects of an esophageal intubation. Every patient was allowed a limit of two attempts at intubation; in the event that one fizzled, a new attempt was promptly performed. If any of the accompanying happened: ( 1) the glottic openness and tracheal intubation time surpassed 120 s; ( 2) the intubation endeavor bombed two times; ( 3) the oxygen immersion dipped under 95%; ( 4) there was a variance of over 25% in either pulse or pulse; or on the other hand (5) there was aviation route injury (as shown by blood staining on the Mac sharp edge or the head end of the tracheal cylinder) — the convention must be ended and the intubation ought to be taken over by the boss.

The event of sore throat was additionally evaluated 24 hours after intubation by staff individuals who didn't know about the patients' gathering. We assessed the degree of uneasiness utilizing a visual simple scale that reaches from 0 to 10 centimeters.

Statistical Analysis

Tracheal intubation success rate was the main result. Collecting glottal and tracheal intubation times, as well as C and L grades, were considered secondary outcomes. The success rate of tracheal intubation was used as the major test criterion to assess the sample size. The DL group had an estimated 50% success rate for tracheal intubation in this trial. A clinically relevant between-group difference in RLGL was defined as 20%; a power of 80% and a two-sided type I error of 0.05 necessitated 93 patients per group. For the sake of fairness, we rounded up to 100 patients in each group such that each operator could handle 10 patients and 5 intubation techniques.

Percentage, rate difference with a 95% CI, mean ± SD, or median (25th and 75th percentiles) were the ways the numbers were presented, depending on what was acceptable. Untrained performers may experience a "quickly" failure in one method and a "slowly" success in another. This might lead to a negative bias as the successful technique's mean time is increased without any impact on the unsuccessful technique. Hence, regardless of the real length, the passed season of all ineffective intubations was recorded as 120 seconds. While looking at the visual properties, we utilized a two-example t-test for constant information and a Pearson chi-square test for all out information. The equity of fluctuations was tried for utilizing consistent information utilizing the Levene test. A different differences t test was utilized in situations when the changes were inconsistent. Using a log-rank test, the term of tracheal intubation and glottic openness were differentiated between the two strategies. To contrast the two gatherings' times with effective tracheal intubation, Kaplan-Meier diagrams were produced. The P-esteems that were all given were two-sided, and importance was characterized as P-values underneath 0.05. Programming from SAS Organization Inc. (Cary, IN) and SPSS Measurements 17.0 (SPSS Inc., Chicago, IL) were utilized to lead the factual examinations.

There were a grand total of 205 tracheal intubations. The analysis did not include five patients because they did not meet the exclusion criteria. According to the supervising anesthesiologists, one patient saw a 40% drop in blood pressure, while the other four patients were classified as C & L grade III.

The procedure did not cause any problems, adverse events, or obvious damage to the individuals.

Table 1 shows that there was no statistically significant difference between the two groups when it came to patient anthropometric data, especially those characteristics pertaining to anaesthesia. The two trial groups were so identical as a result of patient randomization.

Success Rates

Figure 2 shows that both groups had an increase in the number of successful intubations from the first to the fifth attempt, with the RLGL group showing a somewhat stronger trend than the DL group. With a rate difference of 25% and a 95% confidence interval of [11.84%-38.16%], P < 0.001, the RLGL group had a higher overall success rate than the DL group (72% vs. 47%).

Time to Glottic Exposure and Tracheal Intubation

While there was no statistically significant difference between the first and fifth intubation exposure times or intubation durations, all three groups showed a decline in duration with subsequent intubations (table 2). Notably, RLGL allowed for intubation and glottis exposure to occur more quickly than DL. Both the exposure time (27 [15; 42] vs. 45 [30; 73] s, P < 0.001) and the intubation duration (66 [44; 120] vs. 120 [69; 120] s, P < 0.001) were much shorter in the RLGL group compared to the DL group, indicating method-related differences.

One would anticipate a tight correlation between intubation duration and intubation success, given that intubation time decreases with successive intubations (table 2). The Kaplan-Meier graphs in figure clearly show this relationship.

3. For a given intubation time, the success rates were greater with RLGL than with DL. The median intubation time with RLGL was 66 (44; 120) s, compared to 120 (69; 120) s with DL (log-rank test, P < 0.001).”

Exposure of the Glottis

Figures 1D-G show examples of the RLGL group's categorization based on operators' judgements of glottic exposure levels according to C & L grades,12 as shown in table 3. The RLGL group had 80 exposures rated as I or II, whereas the DL group had 57. Additionally, grade IV exposures were somewhat more common in the RLGL group (7 vs. 16) than in the DL group. Thus, it seems that RLGL was superior than DL for glottis exposure.

Specifically, operators in the RLGL group intubated just 28 patients, whereas in the DL group they managed to intubate 53 patients. Table 3 shows that the supervisors who intubated each patient ultimately rated their C & L as an I or II.

C & L = Cormack and Lehane grade; DL = direct laryngoscopy; RLGL = retrograde light-guided laryngoscopy.”

Postoperative Sore Throat

“Compared to the 21 patients intubated using DL, nine patients intubated using RLGL reported a sore throat at 24 hours following intubation (P = 0.017). Comparing the RLGL group to the DL group, we find that the RLGL group had less severe throat pain (2.1 ± 0.9 vs. 3.7 ± 1.0 cm, P = 0.001).

New intubators can intubate patients more quickly and successfully with RLGL than with DL. The random assignment of patients to the intubation methods produced two identical study groups that did not differ in any anesthesia-related variables, including body size, American Society of Anesthesiologists classification, or possible intubation complications (table 1).” Hence, these differences could not have been caused by bias in patient recruitment.

We used inexperienced intubators who had practiced on mannikins to compare the two methods' efficacy before administering them to real patients. To eliminate operator-related bias, we randomly assigned patients to one of two intubation strategies. Also, we recruited 20 novices and had them execute 10 intubations (five using each technique) to reduce the impact of participants' varying levels of technical expertise. Our research appropriately compares the two intubation procedures' performance, thus it's fair to state.5,6

One can question if they can still be considered novices given that each operator conducted 10 intubations. It takes around 50 intubations for a rookie to achieve a 90% success rate, thus the answer is probably yes.1, 2 When compared to other intubation learning curves, our operator success rates are lower. Consequently, it is more probable that the intubation method we used, rather than operator bias, is to blame for the discrepancies in the outcomes across our patient groups.

An essential stage in tracheal intubation is glottis exposure.6,7, 13. The strongly "red glowing"11 glottis was simpler to monitor with RLGL (fig. 1) than DL, according to several of our operators. Furthermore, the whole intubation procedure is efficient and saves time since the illu-minated glottis surrounding the tube disappears following RLGL intubation. The benefit of RLGL over DL may be explained by the fact that the target region has distinct lighting conditions, according to this finding. There are really just two prerequisites for both methods to be successful. To begin, both approaches need that the observer and glottis maintain correct alignment of the optical axis. Secondly, the glottis can only be identified with the right amount of light. In cases when the glottis is not initially visible, DL often creates visibility circumstances that allow one to examine structures nearby, which may be used as key markers to locate it. Even though they are only partially visible, these structures may “also be employed for early orientation in the pharynx/larynx via retrograde light transmission. Because RLGL mostly uses illumination of the glottis and structures cranial to it as a guide, these structures are not needed for glottis exposure (fig. 1D-F). The light at the tunnel's exit serves as a guidepost to the final destination, much like this. The C & L grades moving to lower categories (table 3), shorter exposure and intubation periods (table 2), and most importantly, improved success rates (fig. 3) compared to DL” demonstrate that RLGL does enhance the intubation circumstances, notwithstanding these factors. The reported figures (ranging from 35% to 65%) are consistent with our 47% average success rate in the DL group.1–6

We acknowledge that our work has a number of limitations and flaws, but we believe it is the first to use this novel approach and compare its performance to standard DL. It took more tries for the RLGL group to reach the success requirement of the training process (complete three consecutive intubations) than it did for the DL group because their trainer manikin was a modified version of the standard airway management model, which did not accurately simulate the situation encountered with a real patient. Secondly, the operators knew about both intubation procedures just before they started, therefore the research couldn't be blinded. Thirdly, we only looked at a small subset of healthy individuals who did not seem to have any problems with intubation. Thus, whether RLGL may also aid intubations that are challenging is still up for debate. The use of both RLGL and DL together might make intubation easier in certain situations. Fourth, our anesthesiologist had previously evaluated the flashlight's light intensity on a subset of our patients to ensure it would provide the finest possible view of the laryngeal cavity; this was done in preparation for this research. Sixth, RLGL needed a second helper to steady the torch. Creating a skin-mounted light source has the potential to one day decrease the number of people required for RLGL. “The glottic exposures in the RLGL group could not be evaluated using the standard C & L grading system12, but they were evaluated with a revised version (fig. 1D-G) in this study because of the different light sources and light conditions in the laryngeal cavity between the two groups.” This is the sixth point about RLGL improving C & L grades. Seventh, RLGL reduced the degree of discomfort and the occurrence of postoperative sore throat. Due to the absence of a standardised method to identify laryngeal sequelae and the limited sample size, these data should be regarded with care. Finally, RLGL is an other method of intuition. As an adjunct to standard laryngoscopy, it is a straightforward, low-cost, and easily-learned technique. In our research, intubation is more effective with this approach compared to standard DL. Furthermore, RLGL is a newly described helper approach for tracheal intubation. Additional research is required to determine its optimal functioning and efficacy.

The study's examination of retrograde light-guided laryngoscopy (RLGL) in comparison to direct laryngoscopy (DL) within emergency operative settings uncovered significant advantages attributable to RLGL. Notably, RLGL achieved a higher success rate in tracheal intubations than DL, and demonstrated considerable reductions in both glottic exposure time and overall intubation duration. These improvements hold special significance for novice intubators, who often grapple with a demanding learning curve and initially lower success rates. By enabling a swifter and more precise identification of the glottis via retrograde light transmission, RLGL not only elevates the chances of a successful first-attempt intubation but also contributes to a more streamlined and safer intubation technique. Moreover, the decreased incidence of postoperative sore throat in patients intubated with RLGL suggests a gentler method, potentially reducing patient discomfort and postoperative complications. With these findings, RLGL emerges as a promising alternative to traditional methods, offering to refine the practice of airway management in emergency scenarios by enhancing accessibility, efficiency, and success rates, especially for those early in their medical practice. Future investigations should explore RLGL's broader applications, including its effectiveness in more challenging intubations, and consider incorporating this technique into standard medical training to elevate overall intubation proficiency and patient safety

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