Relationships between onset factors for inducible laryngeal obstruction and laryngeal obstruction initiation timing

Introduction Inducible laryngeal obstruction (Ilo) is defined as inappropriate adduction of the vocal cords on inspiration. Currently, there is no agreed aetiology for Ilo described in literature. Exploration of relationships between patient-reported onset factors and Ilo classification on video laryngoscopy may further understanding of the nature and causes of Ilo. Previous research by our Tertiary Airways service described patient-reported Ilo onset factors in a five category taxonomy: Respiratory, Medical, Psychological, Irritant and Exercise (BTS Winter Meeting, 2017), and classified laryngeal presentation of Ilo on videolaryngoscopy according to the ERS/ACCP (2014) International Consensus nomenclature (BTS Winter Meeting, 2017), including speed of initiation of Ilo symptoms (i.e. fast or slow). Aims and objectives To explore possible relationships between Ilo onset factors and observed speed of Ilo initiation as seen on laryngoscopy. Methods Self-reported Ilo onset factors for 102 patients were compared with videolaryngoscopy classification of initiation timing of Ilo. Results There were significant relationships between Ilo initiation speed and certain onset factors. ‘Slow’ initiation was associated with Medical (e.g. surgery, medication) onset factors (χ 2=4.627, df=1, p=0.031). ‘Fast’ initiation was associated with Respiratory (e.g. Asthma, chest infection) onset factors (χ 2=7.976; df=1; p=0.005). A binary logistic regression assessed the impact of these onset factors on initiation speed. The model was significant (χ2=12 (2, n=102) p=0.002), and explained between 11% and 16% of the variance in onset timing, correctly classifying 74% of cases. Patients with Medical onset factors were five times more likely to have fast Ilo initiation, whilst patients with Respiratory onset factors were two and a half time as likely to have slow Ilo initiation. Conclusions Comparing Ilo onset factors with initiation speed highlighted associations which may help to elucidate relationships between onset factors and subsequent Ilo presentation. The ‘slow’ pattern associated with Medical onset factors may suggest a steady-state physiological or neuropathic aetiology, whereas the ‘fast’ pattern, associated with Respiratory onset factors may indicate mechanisms related to airway hyper-responsiveness