0471 INSPIRATORY FLOW LIMITATION IN A LARGE AMBULATORY COHORT OF SUSPECTED SLEEP APNOEA PATIENTS

Abstract

There is no agreed upon best diagnostic or prognostic metric for sleep apnoea. Novel percentage of inspiratory flow limited breaths, clinical pre-test probability of sleep apnoea from adjusted neck circumference, and usual estimated respiratory disturbance index (eRDI) were compared against Epworth Sleep Scale (ESS), a biomarker of sleep apnoea effect. Complete demographics and polygraphy from 52 395 sequential patients referred for ambulatory sleep apnoea screening (www.sagatech.ca) using the Remmers Sleep Recorder (Sagatech Electronics Ltd., Calgary, Alberta, Canada) were assessed with descriptive analysis, analysis of variance, and Bayes Information Criteria (BIC) selected hierarchical cluster modelling (R 3.3.2, mclust 5.2). Inspiratory flow limitation was quantified breath by breath using an automated algorithm (US patent 8834387). 1.) Reviewing scatter plots showed inspiratory flow limitation remained elevated when eRDI did not with low Epworth scores. 2.) Inspiratory flow limitation, eRDI, and their interaction each had significant correlations with ESS (F: 55.49, 1073.71, 8.82; df = 1; all p << 0.01). 3.) BIC, classification, and density plots of cluster modelling showed three to four distinct groups within the 0 to 20% inspiratory flow limited range. 1.) Quantified breath by breath inspiratory flow limitation remained high in mild sleepiness unlike traditional eRDI. 2.) Inspiratory flow limitation and eRDI separately and together significantly correlated with sleepiness. 3.) Three to four tightly grouped clusters of inspiratory flow limitation severity were discerned, but are of unlikely clinical utility. Further analysis of gender effects is planned. RCPSC.