Cough desensitization treatment: A randomized, sham-controlled pilot trial for patients with refractory chronic cough

Hypertonic Aerosols Hydrate Airways Longer and Reduce Acidification Risk with Nonpermeating Cation and Permeating Anion Salts

Background: Hyperosmolar aerosols appear to promote or suppress upper airway dysfunction caused by dehydration in a composition-dependent manner. We sought to explore this composition dependence experimentally, in an interventional human clinical study, and theoretically, by numerical analysis of upper airway ion and water transport. Methods: In a double-blinded, placebo-controlled clinical study, phonation threshold pressure (PTP) was measured prenasal and postnasal inhalation of hypertonic aerosols of NaCl, KCl, CaCl2, and MgCl2 in seven human subjects. Numerical analysis of water and solute exchanges in the upper airways following deposition of these same aerosols was performed using a mathematical model previously described in the literature. Results: PTP decreased by 9%-22% relative to baseline (p < 0.05) for all salts within the first 30 minutes postadministration, indicating effective laryngeal hydration. Only MgCl2 reduced PTP beyond 90 minutes (21% below baseline at 2 hours postadministration). By numerical analysis, we determined that, while airway water volume up to 15 minutes postdeposition is dictated by osmolarity, after 30 minutes, divalent cation salts, such as MgCl2, better retain airway surface liquid (ASL) volume by slow paracellular clearance of the divalent cation. Fall of CFTR chloride flux with rise in ASL height, a promoter of airway acidification, appears to be a signature of permeating cation (NaCl) and nonpermeating anion (mannitol) aerosol deposition. For hypertonic aerosols that lack permeating cation and include permeating anion (CaCl2 and MgCl2), this acid-trigger signature does not exist. Conclusions: Nonpermeating cation and permeating anion hypertonic aerosols appear to hydrate upper airways longer and, rather than provoke, may reduce laryngeal dysfunction such as cough and bronchoconstriction.

Management of non-pharmacologic therapy for chronic refractory cough: Mechanism, composition, applicable population, and assessment

Chronic cough is common in the clinic and can seriously affect the quality of life of patients. Following the existing guidelines for treatment, refractory chronic cough is defined as a clinical condition in which the cause of the cough remains unclear after comprehensive examination and treatment, or the cause is clear but symptomatic treatment is ineffective. It has been found that non-pharmacologic therapy can effectively improve the quality of life and reduce the frequency of coughing for some patients with refractory chronic cough. Compared with pharmacological therapy, non-pharmacologic therapy has no obvious adverse effects; therefore, non-pharmacologic therapy has good application prospects in the diagnosis and treatment of refractory chronic cough. This paper summarizes the composition, indication, action and mechanism of non-pharmacologic therapy in the diagnosis and treatment of refractory chronic cough and prospects for research on non-pharmacologic therapy.

State of the Art for Refractory Cough: Multidisciplinary Approach

Chronic cough is a common problem that can be refractory to medical treatment. Nonpharmaceutical management of chronic cough has an important role in well selected patients. This review article outlines the history of chronic cough management, current approaches to speech pathology management of the condition and new modalities of nonpharmaceutical treatment. There is a need for further research into nonpharmaceutical options with well described randomised control trials.

Cross-country skiers often experience respiratory symptoms during and after exercise but have a low prevalence of prolonged cough

Background

Cross-country skiers train and compete during the winter for long periods of time in subfreezing conditions, which strains the airways and provokes respiratory symptoms. This study aimed to compare the prevalence of exercise-related symptoms and prolonged cough in competitive cross-country skiers versus the general population and to investigate the association between these symptoms and asthma.

Methods

A questionnaire was sent to Finnish cross-country skiers (n=1282) and a random sample of the general population (n=1754), with response rates of 26.9% and 19.0%, respectively.

Results

Both groups were mostly asymptomatic at rest, but symptoms were increased in both groups during and after exercise. Cough was more prevalent after exercise in skiers and phlegm production was more common during and after exercise in skiers. Asthma did not provoke specific symptoms, but symptom prevalence was higher in asthmatic individuals. Skiers had a higher prevalence of cough after exercise (60.6% vs 22.8%, p<0.001) compared with controls, but controls had a higher prevalence of prolonged cough (4.1% vs 9.6%, p=0.004). In participants without asthma, cold air triggered symptoms more often in skiers than controls, while strong odours triggered symptoms more often in asthmatic controls than skiers. Chronic cough lasting more than 8 weeks was rare, reported by 4.8% of controls and 2.0% of skiers.

Conclusion

Cross-country skiers, especially those with asthma, experience a higher burden of exercise-related respiratory symptoms compared with controls. However, repeated exposure to cold air does not appear to result in long-term hypersensitivity of the cough reflex arc.

Cough desensitization treatment for patients with refractory chronic cough: results of a second pilot randomized control trial

OBJECTIVE

The purpose of this study was to collect pilot efficacy data on a novel treatment for refractory chronic cough (RCC), which we call cough desensitization treatment (CDT).

DESIGN AND METHODS

In this parallel cohort, sham-controlled, randomized controlled trial, 21 adults with RCC were randomly assigned to 12 sessions of either CDT (progressive doses of aerosolized capsaicin while behaviorally suppressing cough; n = 11) or a sham treatment (repeated exposure to aerosolized saline; n = 9). The Leicester Cough Questionnaire (LCQ) was the primary outcome measure. Perceived cough severity with a visual analogue scale and cough challenge testing (for measuring cough-reflex sensitivity) were secondary outcome measures. Data were analyzed with mixed effects linear regression and follow-up contrasts.

RESULTS

Results on all measures favored CDT. Excluding one sham participant, whose baseline LCQ scores were deemed unreliable, mean change in LCQ at 3-weeks post treatment was 6.35 and 2.17 in the CDT and sham groups, respectively. There was moderate to strong evidence of a greater improvement in the CDT group in total LCQ score (p = .058) and LCQ Psychological domain (p = .026) and Physical domain (p = .045) scores. Strong evidence was found for a greater reduction in urge-to-cough during CCT in the CDT group (p = .037) and marginal for a reduction in the capsaicin cough-reflex sensitivity (p = .094). There was weak evidence of a greater reduction in cough severity in the CDT group (p = .103).

DISCUSSION

Although the study is limited due to the small sample size, the data provide additional evidence supporting further research on CDT. CDT resulted in a greater change in the primary efficacy measure (LCQ) than both pharmaceutical and behavioral treatments currently found in the literature.

TRIAL REGISTRATION

This trial (NCT05226299) was registered on Clinicaltrials.gov on 07/02/2022.

Characterization of Ethyl Butyrate-Induced Cough Before and After Breath Control Techniques in Healthy Adults

PURPOSE

Methods for cough elicitation frequently involve aerosolized tussive agents. Here, we sought to determine whether healthy individuals demonstrate a quantifiable cough response after inhaling a volatile ester and if breath control techniques modify this chemically induced cough response.

METHOD

Sixty adult male and female participants inhaled prepared liquid dilutions of ethyl butyrate dissolved in paraffin oil at 20%, 40%, and 60% v/v concentrations in triplicate, with presentation order randomized. We delivered stimuli through a face mask connected to an olfactometer and respiratory pneumotachograph. Participants rated sensations of their urge to cough and pleasantness of the odor while cough airflow was measured. Following baseline testing, participants were randomized to implement pursed-lip breathing or slow-paced breathing after inhaling ethyl butyrate to determine the effects of breath control on cough measures.

RESULTS

Inhaled ethyl butyrate elicited cough in 70% of participants. Higher concentrations of ethyl butyrate resulted in significantly greater sensation of the urge to cough, F(2, 80) = 10.72, p < .001, and significantly more generated coughs, F(2, 63) = 13.14, p < .001. Compared to baseline, participants rated significantly decreased urge to cough during breath control techniques, F(1, 40) = 11.01, p = .0019. No significant changes were observed in the number of generated coughs between baseline and breath control techniques, F(1, 31) = 7.23, p = .01.

CONCLUSIONS

Airborne ethyl butyrate is a tussigenic agent in humans. Our findings provide opportunities for future research directions in normal and disordered cough responses to volatile compounds.