INTRODUCTION
Tracheal intubation is the preferred technique for mechanical ventilation. However, standard tracheal intubation via conventional direct laryngoscopy (DLS), performed by untrained medical personnel has high incidence of failure. Success rate by medical support staff, medical students and novice anaesthesia residents is stated to be between 35% and 65%.[1] Alternative approaches for improving the success rates include use of videolaryngoscopy (VLS), which provides better view of the glottis and higher success rate.[2] It does not depend on alignment of the optical axes in the pharynx and mouth.[3] It is more effective but can be time-consuming but the steepness of the learning curve may be less than that with DLS for a novice.[4] The main hurdle in DLS with Macintosh laryngoscope is the visual restriction inherent to the procedure caused by a need to get straight line of sight to visualise the glottis, blade flange, tongue and epiglottis making the procedure monocular at the level of the larynx.[5]
Video laryngoscopes (VLS) represent a breakthrough in airway management. They are available in various designs and blade shapes, with specific applications in selected case groups. Most of the VLS available in market are cumbersome to use and expensive. The need of the hour is a user-friendly and economical VLS. TAScope (The Anaesthetist Society scope) is an indigenously designed VLS by a fraternity member. It is a channelled, anatomically angulated video intubation aid with an endoscopic camera which can be connected to mobile phones and tablets.[6] After satisfactory manikin trial in the institute, this preliminary human study was done to evaluate TAScope in comparison to Macintosh laryngoscope.
METHODS
This preliminary cross-sectional clinical trial was conducted with a convenience sample of 60 participants who were posted for different surgeries under general anaesthesia over one month, after getting permission from the Institutional Ethical Committee. Patients aged 20–60 years, belonging to American Society of Anaesthesiologists physical status 1 or 2 of either sex, Body Mass Index (BMI) <30 kg/m2, Mallampatti airway Class 1 or 2, requiring general anaesthesia and endotracheal intubation were enrolled. Subjects with mouth opening <1.5 fingers were excluded from the study. After obtaining written informed consent, patients were randomly allocated by simple random sampling to two groups of 30 in each group; group TAS (TAS scopy) and group DLS (Macintosh laryngoscopy). Anaesthesia induction and monitoring were standardised for both the groups. Second year anaesthesia residents performed oro-tracheal intubation. After every laryngoscopy, the scope was sterilised with cleaning and immersion in Cidex® (2.4% glutaraldehyde) for 20 minutes for sterilisation.
The primary outcome criteria were laryngoscopy view (Cormack-Lehane grade- CL Grade) and number of intubation attempts. An intubation attempt was defined as an introduction of the laryngoscope blade into mouth and its removal regardless of whether an ETT was successfully inserted.[7] More than 3 attempts were considered as failure of intubation. Secondary outcomes included manoeuvres used to facilitate intubation and Time to Intubation (TTI). External laryngeal manipulation was given when demanded by the laryngoscopist in the form of backward, upward and rightward pressure (BURP) at the thyroid eminence. TTI was defined as the time from insertion of laryngoscope beyond incisors until successful intubation confirmed on three consecutive breaths on capnography.
Results were statistically analysed using EPI info software version 7.1. The quantitative variables were expressed in numbers, mean ± standard deviation (SD) and percentages. After assessing for uniformity of distribution, for quantitative variables, Student's T test and for categorical values, the Chi-square tests (inter-group) were applied. A value of P less than 0.05 was considered significant.
RESULTS
All the 60 patients were successfully recruited and underwent the intervention without any dropouts. Higher grades of C L laryngeal view (1 and 2) were observed in patients with group TAS as compared to DLS (90% vs 53.3% of patients, P < 0.05). [Table 1] No CL grade 3 larynx was seen with the TAS group. Successful intubation in the first attempt was higher with TAS group as compared to DLS group (93% vs 80%, P < 0.05). None of the patients needed third attempt in the TAS group. There was a greater need for external laryngeal manipulation in DLS group as compared to group TAS (53.3% vs 16.6% of patients, P = 0.006). The overall time for tracheal intubation for all attempts was significantly shorter for the DLS group patients as compared to TAS. Mean Time to Intubation with TAS group was 38.26 ± 6.7s and 27.63 ± 9.1s with DLS group [Table 1].
Table 1.
Comparison of intubation characteristics and performance of TA scope with Macintosh laryngoscope
| C and L Grade | Gr. TAS (n) | Gr. MAC (n) | p |
|---|---|---|---|
| Grade 1 | 27 | 16 | p=0.006 |
| Grade 2 | 3 | 12 | |
| Grade 3 | 0 | 2 | |
| No. of Attempts | |||
| 1 | 28 | 24 | p=0.04* |
| 2 | 2 | 4 | |
| 3 | 0 | 1 | |
| Failure to intubate (>3) | 0 | 1 | |
| External manipulation | |||
| Not required | 25 | 14 | p=0.006 |
| Required | 5 | 16 | |
| Time of intubation (sec) | 38.3±6.7 | 27.6±9.1 | p<0.01 |
*p value for 1st intubation attempt
DISCUSSION
In this study, better CL grades were observed in VLS group in comparison to DLS group. VLS with similar blade angles, such as Pentax Airway Scope® and GlideScope® have been shown to be associated with similar views (97% and 92% patients with Glidescope.[4,8]
Successful intubation in the first attempt was higher in group TAS because the trainer as well as trainee can see the visuals as the laryngoscopy proceeds and trainees can be easily guided. Although statistically significant, clinically it was insignificant (possibly due to the small sample size). In a study using GlideScope®, it was observed that 93% patients could be intubated successfully in first attempt with GlideScope as compared to 51% patients via direct laryngoscopy (P = 0.01).[9] We had similar results possibly because TAS scope has similar blade angulation as GlideScope®.
In DLS, manipulations were required frequently to align airway axes for optimal glottic visualisation. Whereas in TAS, glottis visualisation was better as the camera head becomes the eye and provides the view from near the glottis itself. Viewing angle was 60° in TAS and only 15° in DLS.
The time to intubation was significantly more with TAS group as compared to DLS group. In TAS group, the use of a conduit is mandatory to pass the ETT across the glottis; straight line to insert ETT is lost and hence negotiating tube across this curvature takes longer time. We expect that with more experience, this time can be reduced. However, the times are comparable to the results seen with early publications with use of other VLS, such as with Truview®, Glidescope® and Macintosh where the mean intubation times have been shown to be 39 sec, 44 sec and 23 sec, respectively, in a previous study.[10]
TAScope has anatomically angulated metal blade with a fixed 5.5mm endoscopic camera and a channel to guide bougie [Figure 1]. It can be connected to mobile phones and tablets which act as the video screen. As mobile phones are basic amenity in present age, it cuts down on the cost making it affordable (total cost is < INR 8000). Moreover, no separate charging is required as it is powered by mobile phone battery. Plastic blade has also been made available recently.
Figure 1.
Line diagrams showing blade angulation for TAS scope blade and Macintosh blade, middle picture shows TAScope preconnected to a compatible mobile phone and preloaded with bougie
Limitations exist in the present study as it was impossible to blind the intubating anaesthesiologist to the device being used. Also, the observer recording manoeuvres and Cormack-Lehane grade could not be blinded. We did not include patients with difficult airway and obese patients in this preliminary study.
CONCLUSION
TAScope is an ingenious product with a handy and slim design. Our initial experience showed great flexibility and portability in use. Considering its low cost with comparable intubation data to contemporary VLS it may go a long way in making VLS accessible especially in periphery where resources are limited.
Ethical approval
The study was approved by the Institutional Ethics Committee.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Acknowledgements
We would like to convey special thanks to Dr. Mangal Dave (Consultant Anaesthetist at Gokul super speciality Hospital, Rajkot, India) (the inventor of TAScope) for letting us bring his innovation into experimentation.
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