Cough Data Correlation to Disease-Specific Factors
Cough examination is an integral part of the clinical assessment of patients with respiratory illnesses such as asthma, chronic obstructive lung disease (COPD), congestive heart failure, bronchitis, Covid-19 etc. In addition, cough sounds provide highly relevant information about the respiratory system and its diseases.
The accurate and consistent assessment of cough is essential not only for optimum standards of clinical care but also to drive forward advances in our understanding of cough. Subjective and objective measures show only moderate correlation at best.
These subjective assessments are simple and valuable, providing insight into the impact of the cough on the individual. However, due to their subjectivity, such tools are only a proxy measure of a patient’s perception of actual coughing events rather than a direct assessment of the cough itself.
Objective measurement offers an unbiased quantification of cough as a physiological and pathological phenomenon. A comprehensive assessment of cough requires both measures.
Due to the scope of this post and the constantly-evolving nature of the field, it does not aim to be comprehensive but rather to offer insights on cough variables that can indicate the type and severity of the disease. A focus group study suggests that cough severity is a single notion with three interrelated components: frequency, intensity, and disruption.
Cough frequency
Cough frequency evaluation is regarded as the gold standard for objectively assessing cough. The amount of coughing and the number of coughing fits or episodes, and the time of day, during the day and at night, can all be associated with the frequency of cough using descriptive frequency terms (a little, continuous, constantly, occasional, intermittent). Then, based on the severity of each cough, doctors can plan a diagnosis and potential treatment.
A study discovered moderate correlations between 24-hour cough frequency and various objective and subjective measures of cough severity, implying that these measures provide diverse, maybe complementary, information on cough severity. Finally, the study’s most noteworthy point was an unusually high cough frequency in patients with unexplained chronic cough.
The urge or ‘’tickle’’ that precedes coughing was also counted as a frequency in another study. Although technically not a “cough” as defined by medicine, patients felt this sensation to be an essential facet of the cough experience, indicating that researchers should include it as part of an evaluation instrument.
Healthcare professionals can assess cough frequency objectively with validated cough frequency monitors, including the Leicester Cough Monitor and the VitaloJAK.
Cough reflex sensitivity
Rather than assessing efficacy, this measurement is better used to investigate the mechanisms of action of anti-inflammatory medications. For example, one study identified a considerable overlap in capsaicin cough reflex sensitivity in healthy subjects and patients with respiratory illness. This means that cough in disease is caused by a heightened cough reflex and other, perhaps disease-specific factors.
Cough Intensity
Cough intensity is a key factor of cough severity reported by patients. The intensity of coughing is described as how ‘’deep,’’ ‘’strong,’’ ‘’intense,’’ ‘’hard,’’ or how ‘’harsh’’ the coughing was. Sometimes intense coughing can have broader physical effects, including pain, discomfort, and vomiting.
Cough sound analysis has been well validated for measuring cough frequency, but little research has proven its utility in assessing cough strength. Researchers found cough sound power and energy to correlate highly with physiological measures and subjective perceptions of cough strength.
Although power and energy are highly repeatable metrics, it is crucial to standardize microphone position. As a result, these findings support the use of cough sound as an indicator of cough strength.
Quality of life
Health-related quality of life measures are available to assess the impact of cough using a combination of subjective and objective tools. Healthcare professionals can use these tools to evaluate therapy because they capture additional information not measured by objective tools.
Subjective measures are the most commonly used in clinical settings, either imprecisely through qualitative questioning or more precisely through quantitative assessments that include;
- the Leicester Cough Questionnaire
- cough severity visual analogue scale (VAS)
- cough severity diary (CSD)
- the cough-specific quality of life questionnaire (CQLQ)
Cough Tracking
Cough counts in individual patients are an objective marker of cough severity, variation over time may suggest triggers or aetiologies, and repeated measures following treatments can assess their efficacy. With the broader use of cough monitoring in research, objective cough counts are now becoming primary endpoints in clinical trials of antitussive therapies.
The potential value of cough tracking cannot be overstated; however, technology has been the limiting factor. Past studies insist that the ideal ambulatory cough monitoring system would be portable, compact, and minimally intrusive to the patient and would likely operate for at least 24 hours. In addition, a device of this type should detect all coughs and distinguish them from all other sounds.
Hyfe puts this limitation to test by taking advantage of the rise of smartphone and machine learning technologies. Smartphones provide an ideal platform for a scalable, effective, and smart cough monitoring tool that has the potential to change the way we approach global respiratory health.
Keeping track of your cough might help you figure out whether there’s a link between your cough and things like the time of day or the location. Find out more about cough correlation and how to keep track of your cough in our blog.
References
Birring SS, Matos S, Patel RB, Prudon B, Evans DH, Pavord ID. Cough frequency, cough sensitivity and health status in patients with chronic cough. Respir Med. 2006 Jun;100(6):1105–9. doi: 10.1016/j.rmed.2005.09.023. Epub 2005 Nov 2. PMID: 16266801.
Lee KK, Matos S, Ward K, Rafferty GF, Moxham J, Evans DH, Birring SS. Sound: a non-invasive measure of cough intensity. BMJ Open Respir Res. 2017 May 12;4(1):e000178. doi: 10.1136/bmjresp-2017–000178. PMID: 28725446; PMCID: PMC5501240.
Brignall, Kate & Jayaraman, Bhagyashree & Birring, Surinder. (2008). Quality of Life and Psychosocial Aspects of Cough. Lung. 186 Suppl 1. S55–8. 10.1007/s00408–007–9034-x.
Vizel E, Yigla M, Goryachev Y, et al. Validation of an ambulatory cough detection and counting application using voluntary cough under different conditions. Cough 2010;6:3–8.
French CT, Irwin RS, Fletcher KE, et al. Evaluation of a cough-specific quality-of-life questionnaire. Chest 2002;121:1123–31.
