Chest
Volume 139, Issue 3, March 2011, Pages 569-575
Journal home page for Chest

Original Research
Cough
A Novel Approach to Studying the Relationship Between Subjective and Objective Measures of Cough

https://doi.org/10.1378/chest.10-0438Get rights and content

Background

Currently, no data are available on the relationship between changes in objective and subjective measures of cough, the magnitude of change in cough frequency perceived by patients as clinically meaningful, or the sample sizes required to show significant changes in cough therapeutic trials. Because patients anecdotally report reductions in cough severity while undergoing esophageal testing, we aimed to address these issues by assessing objective and subjective measures of cough with and without an esophageal catheter.

Methods

Twenty-four-hour cough monitoring was performed on two occasions, with and without esophageal impedance/pH monitoring in 62 patients with chronic cough (mean age 56.8 years [SD ± 10.8]; 43 women; median cough duration 3.3 years [interquartile range (IQR), 2.0-10.0]). Cough was assessed objectively measuring coughs per hour and subjectively using a numerical cough score and a visual analog scale (VAS), scored separately for day and night, and then averaged to represent each 24-h period.

Results

Objective cough frequency was reduced by a median of 33.3% (IQR, −68.8% to −13.0%; P < .001) with the catheter. The averaged day and night cough scores and VAS scores also significantly decreased, but changes in these did not correlate with decreases in cough frequency. Sample-size calculations suggested that crossover designs using objective cough frequency may be preferable in therapeutic trials.

Conclusions

These observations provide useful information on the reduction in objective cough frequency scored as an improvement by patients with chronic cough and offer guidance for the design and powering of future therapeutic trials.

Trial registry

ISRCTN; No.: ISRCTN62337037; URL: http://www.controlled-trials.com

Section snippets

Subjects

Patients complaining of chronic cough (> 8 weeks) were recruited from a specialist cough clinic in Manchester, England, over a 24-month period. Current smokers, ex-smokers with < 6 months of abstinence, and subjects taking angiotensin-converting-enzyme inhibitors or opiates were excluded, as were those with a respiratory tract infection in the preceding month or contracted during the study. Ethical approval was granted by the local research ethics committee (South Manchester, No: 05/Q1403/117),

Subjects

Sixty-two subjects with chronic cough (mean age 56.8 years [± SD 10.8], 43 women, median cough duration 3.3 years [interquartile range (IQR) 2.0-10.0]), underwent cough monitoring with and without the esophageal impedance/pH catheter (median time between studies 36 days [IQR 15–49]). Of these, 60 subjects completed the cough and esophageal impedance/pH monitoring (two subjects did not tolerate the catheter), and 57 completed the subjective cough scores and VAS (five subjects failed to return

Discussion

To our knowledge, this is the first study to demonstrate an improvement in objective cough frequency in chronic cough. This study also shows that a reduction by one-third in cough frequency was scored by the majority of patients as an improvement in their condition, suggesting that this change was clinically perceived. Despite this, the patients' subjective impressions of changes in cough severity were not correlated with objective changes in cough frequency. Furthermore, our data suggest that

References (28)

  • K McGuinness et al.

    Automated cough detection: a novel approach [abstract]

    Am J Respir Crit Care Med

    (2007)
  • SC Decalmer et al.

    Chronic cough: how do cough reflex sensitivity and subjective assessments correlate with objective cough counts during ambulatory monitoring?

    Thorax

    (2007)
  • AH Morice et al.

    Recommendations for the management of cough in adults

    Thorax

    (2006)
  • F Zerbib et al.

    Normal values and day-to-day variability of 24-h ambulatory oesophageal impedance-pH monitoring in a Belgian-French cohort of healthy subjects

    Aliment Pharmacol Ther

    (2005)
  • Cited by (0)

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

    Funding/Support: This study was funded by a grant from the Moulton Charitable Trust, and Dr Smith was funded by a Stepping Stones Fellowship from the University of Manchester.

    View full text