Cough causes morbidity and transmits disease yet has been under-researched. The best method for recognising and counting coughs remains unclear. We tested the accuracy of the human ear and measured the influence of visual data on cough counting. We also evaluated PulmoTrack®, a potentially fully-automated cough monitor.
Methods
Consistency amongst listeners and the effect of visual data: Three 14–22-min sequences containing 45–79 coughs were played to 15 respiratory physicians on at least two occasions. Only sound was played on the first occasions but on the final occasion a simultaneous display of audio activity was included. Counts of cough sounds across methods and listeners were compared. Evaluation of PulmoTrack®: 20-h recordings were made from 10 patients with cough. Automated counts were compared with assessment by one investigator.
Results
Agreement among listeners was high. The intraclass correlation coefficient (ICC) for cough counts by ear alone was 0.89 (95% CI, 0.65–1.00). With a concurrent visual display of sound amplitude it was 0.94 (0.80–1.00). 4.8% (0.6–9.5) fewer coughs were counted using visual data than by listening alone (mean [SD] total coughs: 190.2 [3.4] vs 200.7 [14.6]; p = 0.04). Cough frequencies reported by PulmoTrack® and the researcher differed substantially (ICC 0.23, −0.51 to 0.34, p = 0.87); PulmoTrack® had a sensitivity of 26% for detecting coughs identified by ear.
Conclusion
Coughs are well recognised by different listeners. The method used to count coughs should be clearly described as visual information has a significant influence. Non-automated cough counting remains the gold standard method of quantifying cough.
