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Both the hybrid reinforced silicon tube and the matched guidewire are matched for ‘deformation’ and with highly flexible tips, delivering smooth transit through the upper airway and keep the tissue-trauma at minimum.
There is an extended section without reinforcement at the lower end of the tube making it highly flexible* both at vertical as well as transverse axes.
A bench was created to test the resistance to sliding between the various combinations of the prototypes. The video shows the performance of a bougie and a guidewire through the same tube configured in an exaggerated (difficult) angle in the upper airway.
Sliding resistance is negligible with minimal frictional resistance even with extreme bending of the tracheal tube. It enhances smooth, secured railroading without delay.
A dedicated ‘guide-channel’ built inside the wall of the tube for the railroading, frees up the central lumen that may be used to deliver oxygen, monitoring ETCO2 and/ visual confirmation of the progress or position of the tube inside the airway using a flexible viewing scope/camera.
It was tested extensively in human cadavers. The fluoroscopy video shows the control of the trajectory of the tube through the upper airway into the trachea.
Greater inward deformation (‘giving in’) of the non-reinforced section of the tip of the tube at the narrower section of the larynx in a cadaver, as watched from the trachea, looking up.
It is possible to do successful blind (un-assisted) oral intubation in a cadaver with Naga intubation system.
Progress of the Naga tube through the oropharynx, the larynx and into the trachea in the live human subject under anaesthesia.
Retrograde intubation with Naga system
The total control of the trajectory of the tracheal tube over a guidewire in situ is at the heart of success with wire-guided intubation technique; antegrade or retrograde.
Naga system works seamlessly and in unique way for retrograde intubation (as observed in cadavers). The commonly associated issues of misplacement of the tube and the introducer responsible for the failed retrograde intubation can be avoided.
After a guide wire is inserted through either the thyrohyoid or the cricothyroid space and retrieved from the mouth (or nose) :
The tube is directly railroaded over the guidewire to the point of puncture in the larynx.
The displacement of the tracheal tube at this stage from the inadequate depth of insertion [1,2] is avoided the following way.
Sustained pressure at the tube tip creates compression of neck tissues trapped on it, ‘energising’ the soft non-reinforced tip.
2. The force on the guidewire drags on the tissues and the skin in front of the neck at the point of puncture inwards, creating tenting, an indirect confirmation of the presence of the tube inside the larynx. (Illustration and the Video below)
With removal of the guide wire from the top, the trapped tissues relax back to its normal state, and the dimple disappears abruptly (shown below in a cadaver study)
The released tip expands forward down the airway gaining more depth of insertion.
The tube is now advanced further ———
—— to an appropriate depth inside the trachea.
References
1. Lenfant F, Benkhadra M, Trouilloud P, Freysz M. Comparison of two techniques for retrograde tracheal intubation in human fresh cadavers. Anesthesiology 2006;104: 48-51.
2. S S Dhara. Retrograde tracheal intubation. Anaesthesia 2009; 64: 1094-1104.
Publications on Naga system
3. S S Dhara, D J McGlone, M W Skinner Development of a new system for guidewire assisted intubation: mannekin and cadaver evaluation. Anaesthesia 2016; 72(1): 44-9.
4. Ponnusamy T, Kundra P, Rudingwa P, Gopalakrishnan S. Comparison of laryngeal morbidities with modified reinforced silicone tube intubation guided over a bougie vs. a guidewire: novel assessment with voice analysis. Anaesthesia, 2018. 73: 730-737.
5. Sasanka s Dhara, Pankaj Kundra. Complementary deformation of tracheal tubes and flexible introducers: a prerequisite to a secured guided tracheal intubation. J C Monit Comp 2019, 34(2), 381-383.
6. Sasanka Dhara. Naga Tracheal Intubation System. Abstract / Trends in Anaesthesia and Critical Care 30 (2020) e165.
A report of clinical trial of the intubation system in 299 patients is awaiting publication.