A Prospective Observational Study to Identify the Predictors of First Pass Success with Video-Laryngoscope-Guided Nasal Intubation in Patients with Restricted Mouth Opening in Oral Cavity Tumours

Background and Aim: Video-laryngoscopes are commonly used for intubation in patients with restricted mouth openings. However, the predictors of difficult video-laryngoscope-guided intubation have not been clearly defined in the literature. The primary objective of this study was to identify the parameters that predict first-pass success with video-laryngoscope-guided nasal intubation in patients with oral cavity tumours and restricted mouth openings. The secondary objective was to determine the minimum mouth opening above which successful first-attempt intubation with a video-laryngoscope was achieved in this population. Methodology: After Institutional Review Board approval, a single-centre prospective observational study on 30 oral cavity tumour patients with mouth openings <5 cm was conducted. Both conventional and ultrasound-guided airway parameters – intercondylar distance (ICD), tongue thickness, skin to hyoid distance (DSH), skin to epiglottis distance (DSE) and hyomental distance ratio (HMDR) – were measured after screening. Patients were intubated with C-MAC D-Blade video-laryngoscopy. Successful safe video-laryngoscopy intubation is defined as first-attempt intubation, intubation time <60 s, without using any adjuncts and no adverse events. Results: The incidence of safe single-pass intubation was 12.79%, and the incidence of difficult laryngoscopy requiring more than 1 attempt was 17.2%. The mean interincisor distance, which was intubated within 60 s, was 2.97 ± 0.61 cm. Amongst the ultrasound parameters, HMDR was significantly different ( P = 0.05) in two groups requiring more than one attempt at intubation. ICD has a positive correlation with interincisor distance (IID). Conclusion: In patients with oral cavity tumours, restricted mouth opening, HMDR and ICD are the reliable predictors of difficult intubation with a video-laryngoscope. IID of 2.97 ± 0.61 cm was safely intubated within 60 s.