An investigation of different definitions of cough bouts

Coughing bouts are important to patients and may provide mechanistic information additional to cough frequency. Previous work defined bouts as continuous coughing with <2 second pause between coughs but the optimal definition is unclear. We aimed to evaluate the effect of using different inter-cough intervals to define cough bouts. A database of 24h cough sound recordings with cough positions marked was used for analysis. Custom-written software grouped adjacent coughs into bouts depending on their proximity using 20 different time windows (0.5s to 10s, 0.5s increments). For each window, the total number of bouts (+/- single coughs) was quantified and correlated with cough severity visual analogue scores (VAS). Data from 91 refractory chronic cough patients were analysed; 56 female, median(IQR) age 60y(54-67), cough duration 10.1y(0.5-20), 24h cough frequency 429 coughs(274-813), day VAS 49mm(28-63). The number of bouts generated changed little for windows >3s (fig1), whether single coughs were included or not. With single coughs, the 0.5s (r=0.37,p=0.001) and 2s (r=0.35,p<0.001) windows gave the best correlations with cough severity VAS. Without single coughs, r=0.37(p<0.001) for 1,2,2.5 and 3s windows. These data suggest there is little rationale for using time windows above 3s to define cough bouts. Further work is required to assess the effect of different definitions on bout length, total bout duration, cough free time, and numbers of single coughs. <fig><object-id>erj;64/suppl_68/PA3900/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>