Measurement of cough☆
Introduction
Although cough has been a symptom that clinicians have had to deal with for a long time, only recently has serious thoughts been given to its measurement. The measurement of cough both from the clinical point of view and from the research angle has only been seriously undertaken over the last 20 years. Any advances in understanding of cough or in new antitussives can only derive from tools established for measuring cough. Cough can be measured both in subjective or objective ways, the latter by quantifying the events that we all can identify as a ‘cough’. The measurement of cough should include tools that measure both the amount and severity of cough. In addition, other measurements pertaining to cough include the assessment of the cough reflex, which may be an indication of the cough sensitivity, the degree of which may relate to the severity of cough. Cough is a problem that needs to be measured not only in patients in whom cough is the major symptom, but also in patients with chronic respiratory illness where cough may be a predominant symptom. There is a clear need for having both objective and subjective measures of cough for use in clinical practice, clinical research, and in the assessment of new therapies (Chung, 2004). However, more development and validation of these techniques is needed before we can have standardised measures that could be used by every clinician or researcher.
This review will examine three major areas of cough assessment: (i) measurement of cough by impact on health and quality of life; (ii) cough counts and severity; (iii) cough sensitivity. Each of these assessments provide a different aspect of cough but theoretically, there is little reason to doubt that these measurements should not correlate with each other.
Section snippets
Clinical subjective cough measures
Cough has been measured simply by asking the patient to provide his/her own appreciation of the frequency and severity of the cough; usually how the cough is affecting his/her daily living and activities, is obtained. Cough scores, cough diaries, cough symptom questionnaires and use of a visual analogue scale have all been developed although thorough validation of these measures have not been carried out. The notation of the patient, scaling of cough intensity and frequency and patients’
Cough-specific health-related quality of life questionnaires
The fact that chronic cough can have an impact on health status forms the basis of these questionnaires. Patients with chronic cough may seek medical advice for various reasons including worry about the cause of the cough, the presence of serious illness, anxiety, social embarrassment, and associated symptoms such as syncope or urinary incontinence. The more general respiratory questionnaires such as the St. Georges Respiratory questionnaire (SGRQ) contains only two items specific to cough
Definition of cough: what is a cough?
The definition of a cough may not sound too philosophical a question to tackle when it comes to monitoring of cough. Cough is primarily a characteristic sound that can be distinguished by the human ear to be quite unique from other sounds. However, because most cough monitors uses a microphone to record the cough sound, and most software programs are unable to distinguish cough from other closely related sounds, it is necessary to obtain other properties of the cough which could be used to
Early methods
The need for monitoring cough events is recognised by most researchers for a long time. Early methods recorded cough in non-ambulatory patients, usually limited to short periods of time (Barach et al., 1955, Chernish et al., 1963). Pneumographic recording of thoracic pressure change during cough and measurement of airflow have been used to count cough numbers and the use of the cassette recorder using a free-air microphone was described in the 1960s (Loudon and Brown, 1967, Reece et al., 1996).
Can quantitative analysis of the cough sound help in the diagnosis?
An interest in quantitative analysis of the cough sound has been generated with the hope that such analysis may be used for diagnostic purposes, as well as for assessing the severity of the disease process (Korpas et al., 1996). Analysis of the cough sound (the tussiphonogram) can often discern two components, with the first sound originating at the level of the tracheal bifurcation or below, while the second sound probably from the vocal cords. The second cough sound is often absent in
The cough reflex
The cough reflex has been studied using challenges such as low chloride content solutions and using single breath challenges with citric acid or capsaicin (Morice et al., 2001, Fuller, 2003). Capsaicin challenge is currently the challenge of choice used by most investigators, being tolerable and acceptable test, with the possibility of performing reproducible dose–responses (Dicpinigaitis, 2003, Dicpinigaitis and Alva, 2005). Usually the response is measured as the concentration of capsaicin
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2017, Pulmonary Pharmacology and TherapeuticsCitation Excerpt :In addition, in conditions where chronic cough could be a predominant symptom such as asthma, COPD and pulmonary fibrosis, there is a characteristic inflammatory changes for that disease that could interact with cough sensory nerves. Measurement of cough hypersensitivity with citric acid or capsaicin indicate that these patients with chronic cough are usually accompanied by an excessive cough response to these inhaled tussigens, with sometimes correlation obtained between the level of the neuroinflammatory mediators and the degree of this cough tussive response, supporting the value of cough provocation tests in the diagnosis of CHS [16,17]. However, the value of these measurements must be tempered by the observations that successful pharmacological treatment of chronic cough with agents such as slow-release morphine and gabapentin have not always been accompanied by reduction in cough hypersensitivity measured by inhaled capsaicin or citric acid [18,19].
Automatic cough segmentation from non-contact sound recordings in pediatric wards
2015, Biomedical Signal Processing and ControlCitation Excerpt :During consultation sessions physicians may also seek quantitative information on coughs, such as the frequency of occurrence of cough events over a given time interval. This information can be used to determine the nature (e.g., acute, chronic) and the severity of coughs as well as to monitor the efficacy of a treatment [5]. However, to obtain this information, physicians heavily rely on subjective reports of patients or their carers.
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2015, Murray and Nadel's Textbook of Respiratory Medicine: Volume 1,2, Sixth EditionChinese national guideline on diagnosis and management of cough(2021)
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This paper is part of the Special Issue entitled “Cough and its Regulation”, guest-edited by John G. Widdicombe and Bradley J. Undem.