The present and future of cough counting tools

Abstract

The widespread use of cough counting tools has, to date, been limited by a reliance on human input to determine cough frequency. However, over the last two decades advances in digital technology and audio capture have reduced this dependence. As a result, cough frequency is increasingly recognised as a measurable parameter of respiratory disease. Cough frequency is now the gold standard primary endpoint for trials of new treatments for chronic cough, has been investigated as a marker of infectiousness in tuberculosis (TB), and used to demonstrate recovery in exacerbations of chronic obstructive pulmonary disease (COPD).This review discusses the principles of automatic cough detection and summarises key currently and recently used cough counting technology in clinical research. It additionally makes some predictions on future directions in the field based on recent developments. It seems likely that newer approaches to signal processing, the adoption of techniques from automatic speech recognition, and the widespread ownership of mobile devices will help drive forward the development of real-time fully automated ambulatory cough frequency monitoring over the coming years. These changes should allow cough counting systems to transition from their current status as a niche research tool in chronic cough to a much more widely applicable method for assessing, investigating and understanding respiratory disease.

Digital acoustic surveillance for early detection of respiratory disease outbreaks in Spain: a protocol for an observational study

“…Attempts to achieve this date back to the 1950s, but until recently, important technological constraints limited significant advances. 5 Even now, detecting and classifying sounds as coughs without the input of a human observer still represent a remarkable challenge. However, automatically detecting cough is now possible thanks to the development of acoustics and artificial intelligence (AI) models which can be incorporated into wearable devices.…”

“…This has allowed the development of several alternatives, whose widespread deployment beyond a research context remains limited due to problems related to portability, the need to continuously record sound (which may compromise patients' privacy), inconsistent sensitivity and specificity, high false positivity rates and little financial incentives. 5 Some of these limitations might be addressed by incorporating similar systems on smartphone applications, an approach that has just recently begun to be widely explored. 6 7 In brief, putative cough sounds (manifested as short and explosive noises) are recognised and captured by smartphones.…”

Feasibility and clinical utility of ambulatory cough monitoring in an outpatient clinical setting: a real-world retrospective evaluation

“…Cough frequency monitoring is one of several tools available to assess cough. While it provides objective quantification of cough frequency, it is rarely utilised outside of research settings and therefore the clinical utility of cough frequency monitoring in clinical practice has not been established (3). Ambulatory cough frequency monitoring is more valid and reliable than patient recall and clinician estimation (4,5).…”

Predictive Value of Cough Frequency in Addition to Aspiration Risk for Increased Risk of Pneumonia in Dysphagic Stroke Survivors: A Clinical Pilot Study

“…In principle, three main aspects of cough are of interest in clinical settings: reflex cough sensitivity, volitional cough strength, and frequency of spontaneous cough [20]. The frequency of coughing is measured primarily in research on respiratory diseases, which cause refractory cough [21] and can inform about the severity of a refractory cough as well as about the etiology of the disease [22]. In connection with dysphagia, most cough research has focused on assessing reflex cough sensitivity or volitional cough strength, but there has been very little research on the role of cough frequency in the context of post-stroke dysphagia [23].…”

“…One example of such a cough monitor device is the LEOSound system [26]. LEOSound ® is a validated, fully automated lung sound monitor, which works as "long-term stethoscope" and enables continuous objective respiratory sound auscultation for up to 24 h. The device detects, measures, and counts cough events with a sensitivity of 93% and a specificity of 99% [22,26]. The results of long-term cough recordings could potentially provide important information to enhance the results of the dysphagia diagnosis.…”