title: 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.
  
  
  METHODS
  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 = <0.01]. Median log concentration of citric acid eliciting five coughs (C5) was - 0.9 mol/L (range, - 1.5 to 0.0 mol/L). Day time but not overnight time spent coughing was significantly correlated with log C5 (log C5 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 = <0.01, and 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.
authors.affiliation: North West Lung Research Centre, South Manchester University Hospitals Trust, UK. jacky.smith@manchester.ac.uk
authors.forename: Jaclyn
authors.initials: J
authors.lastname: Smith
authors.forename: Emily
authors.initials: E
authors.lastname: Owen
authors.forename: John
authors.initials: J
authors.lastname: Earis
authors.forename: Ashley
authors.initials: A
authors.lastname: Woodcock
mesh_terms: D000368:Aged; D002940:Circadian Rhythm; D003371:Cough / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D015994:Incidence; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods*; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications* / Q000503:physiopathology; D011788:Quality of Life; D012307:Risk Factors; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires