Cough in COPD: Correlation of Objective Monitoring With Cough Challenge and Subjective Assessments

Abstract

Background The relationships between objective cough rates, cough reflex sensitivity, subjective estimates of cough frequency, and cough-related quality of life in patients with COPD are poorly understood. Subjects Twenty-six patients with stable COPD who complained of cough (76.9% men; mean ± SD age, 68.7 ± 6.9 years; mean FEV 1 , 54.2 ± 12.0% of predicted; median smoking history, 42.4 pack-years [range, 13 to 135 pack-years]). Methods Subjects performed a cough challenge test, ambulatory daytime and overnight sound recordings, scored the severity of cough (0 to 5 score and visual analog scale) for each recording period, and completed a cough-specific quality of life questionnaire (CQLQ). Coughs were counted manually and quantified in terms of cough seconds per hour (cs/h): the number of seconds within the recording that contain cough. Results Overall median time spent coughing was 7.5 cs/h (range, 2.7 to 23.1 cs/h; daytime median, 12.4 cs/h [range, 3.3 to 40.4 cs/h]; overnight, 1.9 cs/h [0.0 to 19.0 cs/h]) [p = r = − 0.49, p=0.02, and r = − 0.20, p=0.37, respectively). Subjective cough scores and visual analog scales were moderately associated with objective time spent coughing: daytime ( r = 0.37, p=0.03, and r = 0.41, p=0.03) and overnight ( r = 0.48, p= r = 0.5, p=0.01), respectively. Conclusions Subjective measures of cough and cough reflex sensitivity are statistically related to time spent coughing in patients with COPD, but with low-to-moderate levels of correlation. These measures have insufficient predictive value to substitute for objective time spent coughing; however, in conjunction with the CQLQ, they may provide a qualitative dimension to the assessment of cough.