Objective monitoring of cough in children with cystic fibrosis

Increased cough frequency is a common symptom associated with infective pulmonary exacerbations of cystic fibrosis (CF), but subjective assessment of cough is very unreliable. The aims of this study were: 1) to validate a modification of our previously described ambulatory cough recording device (LR 100); 2) to determine how accurately children with CF assess levels of cough; and 3) to assess the change in cough in children with CF when treated with intravenous antibiotics for a respiratory exacerbation, and whether the children themselves were able accurately to perceive any change. Fourteen CF children (aged 13.6 +/- 2.6 years) were included in the study. All 14 children were simultaneously recorded with the LR 100 cough recorder and a conventional tape recorder during a chest physiotherapy session on the first or second day of admission for an infective exacerbation diagnosed by standard criteria. The difference between the two was an underestimate of 0.5 epoch/session by the tape recorder. Ten children were recorded on admission with the LR 100 cough recorder for a complete cycle (17 hr and 40 min), and we also assessed their day and night-time cough with cough scores and visual analogue scores (VAS). In 8 of these children, the same assessments were repeated on discharge. There was no significant correlation between any of the admission or discharge cough scores, daytime or night-time cough scores, and daytime or night-time VAS scores, with the actual number of coughs recorded on the LR 100 cough recorder. For the 8 children who had cough monitoring on admission and on discharge, there was no significant improvement in daytime or night-time cough scores or VAS on discharge, despite significant improvements in spirometry. There was also no significant improvement on daytime and night-time cough counts with the cough monitor on discharge, and no significant correlation with changes in lung function. There were weak correlations only between change in daytime VAS scores and change in forced expired volume in 1 sec (r = -0.794, P = 0.019) and forced vital capacity (r = -0.723, P = 0.04). In conclusion, we describe a reliable and well-tolerated method for obtaining cough counts objectively. The use of this objective method showed that CF children did not assess their cough frequency well. In addition, treatment of respiratory exacerbation improved neither subjective nor objective measures of cough in CF children.