Laryngoscopy is the basic skill of any anaesthesiologist but this approach cannot be universally applied for securing the airway. Syndromic patients, acquired conditions like ankylosing spondylitis, rheumatoid arthritis, airway trauma and the list continues, wherein the use of traditional laryngoscopy is guarded.10,11 It is equivalent to using typewriters in the era of word processors. The era of real time digital technology not only warrants but mandates using real time visualisation through minimally invasive technique.
Ultrasonography has already been accepted for most airway related diagnostics and procedures, but its use for securing the airway under dynamic guidance is still to be explored. Point of care ultrasound perioperatively has been expanding by leaps and bounds and it is not only imperative but rather an absolute necessity, that we start using dynamic ultrasound guidance in the core practice anaesthesia, that is, in airway management.
The first case report on UGTI was published in 2012 wherein the authors identified the posterior hypopharynx at the level of the thyrohyoid membrane by its hypoechoic appearance and vocal ligaments as linear hyperechoic structures that abducted with mask ventilation.6 Under dynamic guidance using a linear probe, the endotracheal intubation was performed and trajectory of tube was modified to place it through the glottic opening. Widening of the cords and enhanced posterior shadowing of the trachea was observed when the tube entered the glottis.
Following this there was another study wherein the authors compared UGTI with optical stylet based intubation7 and found that UGTI is possible and was as effective as optical stylet based intubation. But, till date the exact technique and methodology to perform UGTI has not been defined. Also, the lodgement of tube onto arytenoids has been mentioned in literature, for which, we further modified the technique by prehand ultrasound guided determination of angulation of ET tube.
Initially we tried using the classically taught 70 to 90 degree hockey stick angulation of the tube in few patients for UGTI but we also, encountered difficulty. Thereafter we modified the technique by pre aligning the tube using the angulation determined by real time sonography between tracheal line and oropharynx and bending the tube through same angle. With this technique we were able to perform intubations with a success rate of 76.6%.
The first resistance encountered is usually at the base of tongue which can easily be overcome by lifting the jaw and further, the second obstruction faced is at the entry of glottis wherein tube hits the arytenoids. We also faced this in the initial attempts in first 10 patients, but we easily overcame this by pre aligning of tube and also slightly increasing the head extension and applying external laryngeal pressure can further act as an aid. The tube has to be progressed gently and softly, visualising movements of soft tissues on ultrasound and rotating the tube to keep it midline. We were not able to secure the tube in 7 patients wherein the tube got stuck most probably on arytenoids and false vocal cords and despite our best efforts we were not able to secure it. Also, we avoided pushing it hard to prevent injury. These patients were then intubated by traditional laryngoscope guided intubation. This also emphasizes the fact that there is a definite learning curve in UGTI as is true in other interventions.
Though it is difficult to establish the technique through small number of patients we undertook but we tried to clearly define the methodology as a basis for future research (as we are also undertaking) and refinement of the technique if required. UGTI has clear cut advantages over traditional laryngoscopy and also the hemodynamic perturbations can be avoided by avoiding direct laryngoscopy. With gradual practice, the use of UGTI can be extended in cases with difficult airway where the mouth opening is restricted. The only viable option here is the fiberoptic and UGTI can counter some of its disadvantages like need of costly equipment, difficulty to visualise in case of bleeding and need for entering a patent nasopharyngeal pathway. Also, fiberoptic intubation requires a steep learning curve, on the other hand, UGTI requires just a thorough understanding of ultrasound guided airway anatomy. Also, among all these assisted intubation techniques, ultrasound is the most widely used equipment nowadays and most anesthesiologists are already well versed with it.