Exploring non-cough expiratory efforts (NCEEs) in refractory chronic cough

_{Above: Dr Terence Taylor presents at the ERS Cough Conference in London, July 2026}

Objective cough frequency remains one of the most established and valuable endpoints in chronic cough research. Through the VitaloJAK® cough monitoring system, Vitalograph has supported more than 60 research studies, analysed over 57,000 recording sessions, and counted more than 33 million coughs. This extensive experience has provided a unique opportunity to observe patterns that extend beyond classical cough events.

During routine cough analysis, trained analysts frequently encounter other audible expiratory effort sounds that do not cleanly fit the agreed definition of a cough used in cough research literature. These may include throat clears, grunts, and ambiguous expiratory effort sounds that seem to fall between coughs and other laryngeal or respiratory sounds. While these events are typically excluded from cough counts, they may be relevant in conditions in which patients commonly report symptoms such as throat discomfort and an urge to cough.

As Dr. Taylor emphasised during his presentation, the objective of this work was not to redefine cough or propose a new clinical condition. Instead, it was to share observations from large-scale cough monitoring and explore whether these frequently occurring sound events merit further scientific investigation and discussion.

Introducing Non-Cough Expiratory Efforts (NCEEs)

To facilitate exploration of these sounds, the research team established a practical working label: Non-Cough Expiratory Efforts (NCEEs). The term describes audible expiratory events, such as throat clears and grunts, that may be associated with throat discomfort or ‘urge-to-cough’ but do not meet the classical cough definition or match an individual's characteristic cough pattern.

Importantly, the researchers introduce “NCEE” as an operational label to describe a range of sounds rather than a physiological classification. The category is likely to include a heterogeneous range of phenomena, making it essential to first determine whether these events can be measured consistently before assessing any potential clinical significance.

A Proof-of-Concept Study

The featured poster presented findings from a retrospective proof-of-concept study using 24-hour VitaloJAK recordings from ten subjects with refractory or unexplained chronic cough. All participants reported meaningful throat discomfort, with throat discomfort visual analogue scale (VAS) scores of at least 55.

Researchers developed a structured annotation framework in which trained analysts first identified and labelled classical cough sounds and then separately annotated candidate NCEE events using predefined rules related to event onset, timing, and separation. The goal was not to create a definitive taxonomy, but to establish a repeatable method capable of quantifying these observations.

The findings demonstrated that NCEEs were both measurable and relatively common within the pilot dataset. Median cough counts reached 712.5 events per recording, while median NCEE counts were 109.5. However, NCEE occurrence varied substantially between individuals, ranging from 0 to 345 events per recording.

Interestingly, the relationship between cough frequency and NCEE frequency was not consistent across subjects. Some participants with relatively modest cough counts demonstrated a high burden of NCEEs, while others with substantial cough frequency exhibited very few NCEEs. This variability suggests that NCEEs may represent a distinct aspect of patient experience rather than simply mirroring cough frequency. However, the researchers caution that the sample size is too small to draw conclusions regarding clinical relevance.

The presentation highlighted several important next steps for future research. First, the annotation framework must be rigorously tested to determine whether different analysts can consistently identify NCEE events. Second, clinical validation of the concept will be needed to explore whether NCEE measurements relate to recognised outcomes such as throat discomfort, urge-to-cough, quality-of-life measures, or specific patient phenotypes. Finally, researchers must determine whether NCEEs provide meaningful information beyond existing endpoints such as cough frequency and cough bouts.

While still exploratory, this work demonstrates how large-scale ambulatory cough monitoring can generate new research questions that may ultimately deepen our understanding of chronic cough and its impact on patients. As Dr. Taylor concluded, if these events can be measured consistently, the key question becomes whether they represent clinically meaningful signals and, if so, how they should best be characterised.