Assessment of scoring systems to describe the position of tracheostomy tubes within the airway - the lunar study

Background: Malposition of tracheostomy tubes is difficult to detect at the bedside and may contribute to eventual device misplacement. Endoscopic examination can be undertaken via tracheoscopic (T-view) or trans-laryngeal (L-view) approach, offering more precise detail regarding positioning within the airway. The aims of this study were to evaluate inter-rater agreement between bespoke T and L view scoring systems and subsequently whether T-views could predict L-views.

Methods: Adult intensive care unit patients with percutaneous or surgical tracheostomies were included and paired T and L-views of their tracheostomy tube within the airway were taken on up to four occasions. Images were later scored by five independent raters using bespoke scoring systems. The primary outcome was to determine the T and L view scoring system with the best inter-rater agreement, defined by weighted kappa and intra-class correlation coefficients. The secondary outcome was to assess agreement between T and L-view scoring systems.

Results: Seventy-one T-views and 43 L-views were obtained from a total of 20 patients. Images were scored by five raters, resulting in 355 T-view scores, 215 L-view scores and 215 paired T and L-view scores for comparison. There was good inter-rater agreement (highest T-view k = 0.84, L-view k = 0.72). There was poor agreement between T and L-view scores for each of the paired images (highest k = 0.25) although extreme-to-extreme misclassification rates remained acceptable.

Conclusions: Whilst our data demonstrated good inter-rater agreement between scoring systems, it is not possible to reliably predict the T-view orientation and position of a tracheostomy tube within the airway from the paired L-view.

Clinical trial registration: NCT01356719

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