|Year : 2021 | Volume
| Issue : 2 | Page : 98-103
Tracheal intubation using a videolaryngoscope assisted by transtracheal illumination with an LED vein finder
Kinna G Shah, Jayshree Thakkar
Department of Anesthesia, Gujarat Cancer and Research Institute, BJ Medical College, Ahmedabad, Gujarat, India
|Date of Submission||21-May-2021|
|Date of Acceptance||06-Jul-2021|
|Date of Web Publication||10-Aug-2021|
Dr. Kinna G Shah
Model House, Shastri Park, Nehrunager Cross Roads, Ambawadi, Ahmedabad - 380 016, Gujarat
Source of Support: None, Conflict of Interest: None
Introduction: Retrograde illumination of the glottis using an LED vein finder placed over the cricothyroid membrane produces a red-orange glow of light inside the airway that can be used to assist the intubator during videolaryngoscopy. The endotracheal tube can be guided through this red-orange glow illuminating the glottis and trachea. Patients and Methods: In this prospective, randomised, single-blinded study, a total of 200 patients posted for elective head and neck cancer surgeries were included. Patients were placed supine with their heads in a neutral position without a pillow. Intubation was done with The Anesthetist Scope videolaryngoscope in Group TI (transillumination) with an assistant holding the LED vein finder over the cricothyroid membrane. The glottic opening was identified by a red-orange glow within the airway and the intubation was performed. In Group C (conventional direct laryngoscopy), transillumination was not done during intubation. Exposure time was taken from the time when the patient's mouth was opened to the time when the best glottic view was obtained. Intubation time was noted from the introduction of the videolaryngoscope or conventional laryngoscope into the mouth, through successful intubation and identification of 3 complete capnographic waveforms. A total of three attempts were allowed for each patient. Results: The success rate was better in Group TI. Exposure time and intubation time were shorter in Group TI as compared to Group C. In three patients with carcinoma of the vocal cords, the glottic opening was identified only by retrograde light transmission from the vein finder. Conclusion: A combination of videolaryngoscopy and LED vein finder is an effective method to achieve a better success rate of tracheal intubation.
Keywords: Intubation, LED vein finder, transillumination-assisted intubation, videolaryngoscopy
|How to cite this article:|
Shah KG, Thakkar J. Tracheal intubation using a videolaryngoscope assisted by transtracheal illumination with an LED vein finder. Airway 2021;4:98-103
|How to cite this URL:|
Shah KG, Thakkar J. Tracheal intubation using a videolaryngoscope assisted by transtracheal illumination with an LED vein finder. Airway [serial online] 2021 [cited 2021 Dec 2];4:98-103. Available from: https://www.arwy.org/text.asp?2021/4/2/98/323565
| Introduction|| |
While many new tools have been developed to facilitate airway management, direct laryngoscopy (DL) still remains the most commonly practiced method of performing tracheal intubation. As stated by Yang et al., the alternatives are costlier, more technically complicated or are not universally available. The 'gold standard' for securing a definitive airway still remains the passage of a tracheal tube through the glottis under direct vision. Though this can be achieved using a relatively expensive flexible bronchoscope, this technique requires a skilled operator and a dry oral cavity. Besides, a sterile bronchoscope may not always be immediately available.
Near-infrared spectroscopy, a technique that makes use of the electromagnetic spectrum (from 740 nm to 760 nm), permits visualisation of veins situated 3 to 5 mm under the skin. Transillumination of the anterior tissues of the neck by infrared or LED light is a good alternative for viewing the vocal cords using a videolaryngoscope.
Biro et al. concluded that infrared retrograde transillumination method could assist videolaryngoscopy by selectively highlighting the relevant structures of the upper airway. Emitted light is invisible to the naked eye, but as videolaryngoscopes have no infrared filter, they can translate it to visible light on the monitor screen, exclusively highlighting the glottic opening. Infrared light cannot be picked up by the naked eye and therefore does not work with DL. The use of an LED light is a simple approach to intubation. Identification of the red-orange glow during videolaryngoscopy or naked eye tracheal intubation can help to identify laryngeal structures. The purpose of this study was to test the feasibility of glottic exposure and intubation success with videolaryngoscope using retrograde illumination by LED vein finder and comparing it with conventional DL.
| Patients and Methods|| |
In this prospective, randomised, open-label, parallel-arm superiority study, a total of 200 patients posted for head and neck cancer surgery under general anaesthesia were recruited. After obtaining Institutional Ethics Committee clearance and informed consent from patients, we randomly allocated 100 patients to each group using a concealed envelope method. In Group C, conventional DL was performed with Macintosh blade #3 or #4. Laryngoscopy was performed in Group TI by using The Anesthetist Scope (TAS) videolaryngoscope (The Rajvi Enterprise, Rajkot, Gujarat, India) with reusable nonchannelled blades. Patient characteristics were documented preoperatively by the anaesthesiologist who was blinded to the design of this study. This anaesthesiologist needed to have the experience of performing at least 20 laryngoscopies each with both types of laryngoscopes. In addition, they needed to know how to use the vein finder.
A modified Mallampati class of I or II, a thyromental distance ≥6 cm and a mouth opening ≥2 cm were essential inclusion criteria. Preoperative tracheostomy, Cormack-Lehane grade 3 or 4 documented during previous anaesthetic exposure, body mass index >30 kg/m2 and presence of temporomandibular joint disease constituted exclusion criteria.
Patients were monitored with the help of a standard electrocardiogram, noninvasive blood pressure, pulse oximetry and capnography. Preoxygenation was performed for 6 min before induction of general anaesthesia. Exposure and intubation times were measured with a stopwatch. The OticaTM Paediatric LED 'O' shape vein finder was use in our study. The LED vein finder was placed over the cricothyroid membrane and the laryngeal inlet was identified by a red-orange light glow during videolaryngoscopy [Figure 1]. The Cormack-Lehane grading was done as follows. When the glottis was seen fully or partially, the view corresponded to Cormack-Lehane Grade 1 or 2. When neither the glottis nor the epiglottis was seen, the view was graded as Cormack-Lehane Grade 3. Finally, when the glottis was not visible but could still be localised by a red-orange glow in the background with no anatomical demarcation, the view was graded as Cormack-Lehane Grade 4.
|Figure 1: Otica™ Paediatric LED ‘O’ shape vein finder placed over cricothyroid membrane and red-orange glow visualised on an android phone|
Click here to view
Exposure time was taken from the time when the patient's mouth was opened to the time when the best glottic view was obtained. Intubation time was noted from introduction of the videolaryngoscope or conventional laryngoscope into the mouth, through successful intubation and identification of 3 complete capnographic waveforms. The total time for each intubation was limited to 120 s, and a maximum of 3 attempts were allowed for each patient.
Failure of an attempt was defined by the following: (1) resistance to passing the tube through the glottis, (2) failure to identify the glottis and (3) definite signs of an oesophageal intubation. As our selected patient population included those with carcinoma of the larynx, identification of the vocal cords was not always assured. Should such failure occur, mask ventilation with 100% oxygen was resumed between intubation attempts. A standby team was available to perform tracheostomy should an airway emergency arise.
The following drugs were administered intravenously during anaesthetic induction-glycopyrrolate (0.02 mg/kg), lignocaine (1.5 mg/kg), propofol (2 mg/kg), fentanyl (2 μg/kg) and succinylcholine 2 mg/kg. Laryngoscopy was performed in Group TI by using TAS videolaryngoscope (The Rajvi Enterprise, Rajkot, Gujarat, India) with reusable nonchanneled blades [Figure 2]. The operator looked for the brightest transilluminated red-orange light in the oral cavity to identify the glottis. If the glottis could not be identified, the LED vein finder was redirected in an upward or sideways direction and glottic identification procedures were repeated. Nasal intubation was done using a 7.0 mm ID Portex endotracheal tube (ETT) for women and 8.0 mm ID Portex ETT for men.
|Figure 2: The Anesthetist Scope videolaryngoscope (The Rajvi Enterprise, Rajkot, Gujarat, India) with reusable nonchanneled blades|
Click here to view
Following anaesthetic induction, the nasal ETT was passed through the preferred nostril. The primary outcome was the intubation time. The secondary outcomes were success rate, number of attempts and complications. In group TI, the following parameters were observed and documented by the person performing the intubation.
- Visible distinction of illuminated laryngeal structures from nonilluminated neighbouring structures (Yes or No)
- Visibility of the glottic opening with the light source on or off according to a subjective visual analogue scale (VAS) from 0 (very poorly visible) to 10 (very well visible).
- Subjective ease of intubation using the device according to a VAS (from 1 = helpful to 10 = not helpful).
Sample size calculation was 63 patients with a confidence level of 95% and a power of 80%. It was therefore decided that a third attempt if needed in group C would be by DL with LED light-guidance. All intubations were observed by the same observer who was in charge of recording experimental results to avoid interobserver bias. This observer also recorded the characteristics of the patients, information on operators and complications. After successful tracheal intubation, the LED vein finder was removed. Maintenance of and recovery from anaesthesia (with sevoflurane and neuromuscular blockade) was conducted according to institutional standards and the individual needs of the patient and surgery.
Statistical analysis was performed using www.graphpad.com. Categorical data were expressed as numbers or percentages. Continuous data were expressed as mean ± standard deviation. Categorical data were analysed using Chi-square test while continuous data were analysed using the Student 't' test. P values <0.05 were considered to be statistically significant.
| Results|| |
Demographic data and external airway measurements were similar in both groups. All patients in both groups were intubated successfully. The number of attempts was similar between the Group TI and Group C (1.15 ± 0.36 vs. 1.35 ± 0.6, P = 0.056). The exposure time was less in Group TI as compared to Group C (7.09 ± 2.52 s vs. 12.72 ± 4.5 s) which was statistically significant (P < 0.001). The intubation time was longer in the Group C as compared to Group TI (50.84 ± 16.88 vs. 39.21 ± 10.78 s; P < 0.001).
In group TI, all 100 patients were successfully intubated within 2 attempts. Seven cases in group TI and 13 patients in Group C were intubated at 2nd attempt; and 1 patient in group C was intubated at 3rd attempt. The success rates of the first, second and third attempts between the two groups are shown in [Table 1]. In addition, the overall intubation success rate was statistically significant between the two groups (100% vs. 97%, P = 0.001).
Intubation was unsuccessful after three attempts in 3 patients in group C because of inability to identify vocal cord anatomy in patients with carcinoma larynx. But they were intubated with the help of light glow by external transillumination obtained using the LED vein finder. Seven patients in group TI had significant pathology in the vocal cord area including sequelae of radiation therapy in carcinoma of the larynx. External transillumination helped in these seven patients to intubate in the second attempt.
Quality of identification of glottic opening in group TI as described by VAS was excellent with external light on as compared to when it was off (87 vs. 13).
| Discussion|| |
Retrograde, external LED-illumination-guided intubation process appears effective and time saving with greater success rates, and shorter exposure and intubation times. Retrograde transtracheal illumination using an LED facilitates tracheal intubation. Use of a vein finder opens up new possibilities. It represents a good alternative device which is less expensive, easy to use and easily available.
Airway pathology and radiation therapy are strong predictors for difficult intubation. Safe airway management in difficult cases demands skilled hands with a unique high success rate. As anaesthesiologists, we must keep ourselves mentally prepared to develop techniques that can make intubation with a videoscope easier, thereby increasing the success rate when it is applied. To improve the success of intubation, various alternatives to conventional laryngoscopy have been described in practice such as the lighted stylet, intubating laryngeal mask,, fibreoptic bronchoscope and videolaryngoscope. However, these alternatives are costly, technically complicated and are not available everywhere.
While using a videolaryngoscope, laryngeal exposure is generally straightforward. However, passing the tracheal tube through the glottic inlet and advancing the tube into the trachea can be difficult. Identification of the glottic opening is difficult and challenging even with a videolaryngoscope in patients with carcinoma of vocal cords and larynx. To shine light in the visible range from the anterior surface of the neck in a reverse direction towards the larynx and to view it during DL seems to be useful. Alternatively, infrared/near-infrared light, with its superior penetrance into hollow organs such as the trachea, seems to be better to explicitly highlight the glottis when using a videoendoscope.
Biro et al. described the use of the Infrared Red Intubation System (IRRIS, Guide in Medical, Nazareth Illit, Israel) to aid videolaryngoscopic tracheal intubation in 40 patients. IRRIS is a new retrograde transillumination device which can emit infrared light through the glottis and enable the operator to locate the glottis on the monitor of the videolaryngoscope. IRRIS may be useful in patients with distorted airway anatomy as seen in laryngeal malignancy.
Infrared light works exclusively with videolaryngoscope, flexible and rigid videoendoscopes that have no inbuilt infrared filter. On the other hand, LED light can be used during DL also. The success rate of intubation with the transillumination-assisted technique were similar for Bonfils and Trachlight intubations (97.3% and 98.7%, respectively). Trachlight is superior for orotracheal intubation with respect to reliability, rapidity and safety compared with the Bonfils fibrescope used with the transillumination technique. Our results were better as our laryngoscopist was experienced with videolaryngoscope and LED vein finder [Table 1].
The trachea of one patient who was initially enrolled in DL was successfully intubated with the Surch-Lite (lighted stylet) after three failed laryngoscopy attempts. We also achieved successful intubation after three failed attempts to identify the larynx in 3 patients using direct laryngoscope and LED vein finder.
The difference in laryngeal visibility on the mobile screen between light on versus light off using LED vein finder device expressed by the VAS was significant (87 vs. 13). In this subjective finding, our experience was very encouraging [Table 1].
This is consistent with the report by Rhee et al. which showed a high success rate with lighted stylet intubation in patients with a history of failed laryngoscopy and intubation. These results suggest that the lighted stylet (in this case, Surch-Lite) can serve as a superior alternative to DL in patients with high Mallampati class.
The important fact about our method is that the glottis is visualised using retrograde transtracheal light transmission from an external light source placed over the skin. We used an LED vein finder which is not expensive, is small-sized and handy. With this approach, the red-orange light glow transmitted across the neck structures helps in easy identification of the glottis. It was always easier to identify the intense red-orange glowing light within the narrow, closed tunnel or cylindrical glottis by using a retrograde LED light (RGL) with videolaryngoscope than by using DL with Macintosh blade. The disappearance of the illuminated glottis around the tube after intubation is evidence of successful intubation while using the retrograde LED light which makes the whole process of identifying a successful intubation easier. Hudson et al. shared a case of failure of laryngoscope bulb who was successfully intubated using a flash light placed directly over the cricothyroid area.
Yang et al. compared tracheal intubation by 20 novices in 205 patients using DL and retrograde light-guided laryngoscopy (RLGL). Intubation was performed faster and with a higher success rate with RLGL than DL. The first attempt success rate was 40% in the RLGL group and 22% in the DL group, and the overall success rate was 72% with RLGL and 47% with DL. One disadvantage of the RLGL technique is the need for an assistant. However, this can be readily mitigated by the use of an illuminated neck collar as a light source, thereby allowing a single provider to perform the technique. The trainees also reported improved Cormack-Lehane grades with RLGL.
| Conclusion|| |
The combination of videolaryngoscopy and LED vein finder to perform retrograde transillumination of the soft tissues of the neck improved the success rate of tracheal intubation with easy glottic exposure and shorter time to achieve tracheal intubation. This technique is a simple, low-cost and easy-to-learn technique that can be implemented with conventional laryngoscopy as the light is visible to the naked eye. The immediate implication is to use this LED vein finder to enhance learning and improve the intubation success rates of novice laryngoscopists.
Our study had the limitation that it could not be blinded because the intubator could see the LED vein finder in use. In addition, an additional assistant was required to hold the vein finder in place. We believe that future studies could be conducted using this technique in children and in emergency intubations performed outside the operating room.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]