Cough Reflex Research Articles

Cough features during a pandemic

The article discusses the clinical and pathogenetic features of cough in patients with coronavirus disease 2019 as a symptom caused by virus-induced damage to respiratory epithelium, olfactory nerve receptor system, and the central regulation of cough reflex. Recommendations on choice of herbal medicines and mucolytic agents are given.

Complications of a posterior fossa post-surgical patient, review of a case

The anesthetic and intensive care unit (ICU) management of patients undergoing posterior fossa neurosurgical procedures represents a true challenge due to the particular anatomy of this region, the vital structures adjacent to it and the possible complications derived from both the intervention itself (surgical) as well as the failed extubation, post-obstructive edema (due to pressure differences in the airway), the absence of swallowing and cough reflexes, mean that the (therapeutic) management is carried out in an optimal, with proper monitoring and decision-making in accordance with the situation. Below is a clinical case of a woman operated on for a posterior fossa tumor who presented airway complications and failed extubation.

Cough Reflex during Dental Treatment under Intravenous Sedation

Cough Reflex during Dental Treatment under Intravenous Sedation

Airway inflammation due to SARS-CoV-2

Although there has been a large number of studies focusing on the role of airways in coronavirus disease 2019 (COVID-19), the relationship still remains unclear. With the disruption of the defense mechanism of the airways, including the intact mucus barrier, ciliary activity, and normal cough reflex, sticky and difficult-to-remove sputum becomes the main problem and the cough becomes the main symptom. Although interferons are considered the main elements of the defense against the virus, the pathogenesis of COVID-19 is complex and cannot be elucidated with only elevated interferon levels; there is more. The progression of the disease is mainly determined by the type and the levels of interferons and the affected part of the respiratory system. The airways have an important role in the pathogenesis of COVID-19, as the microorganism uses the airways as a gateway to the body, being the first element of defense against the virus, the importance of its relationship with the immune system, and its importance in the treatment.

Characteristics of the European Thoracic Society/American Thoracic Society severe asthma definition as a determinant of future use of biologics/bronchial thermoplasty.

BackgroundInternational guidelines define severe uncontrolled asthma. Biologics or bronchial thermoplasty (Bio/BT) are recommended for such patients.ObjectivesTo determine which definitions of severe uncontrolled asthma are associated with an additional Bio/BT treatment in patients with severe uncontrolled asthma.MethodsConsecutive 107 asthmatics (including 15 patients for whom Bio/BT was introduced within 3 months after examination), classified as treatment step 4 according to the Global Initiative for Asthma 2015 guideline, were eligible for this analysis. Patients were assessed using the European Thoracic Society/American Thoracic Society (ERS/ATS) severe uncontrolled asthma guideline as defined by these 4 characteristics: poor control (ACT < 20), frequent exacerbations (≥2/yr), admissions (≥1/yr), and airflow limitation (forced expiratory volume in 1 second < 80% of predicted), along with comorbidities, and biomarkers, including blood granulocytes, fractional nitric oxide, and capsaicin cough reflex sensitivity (C-CS). These indices were compared between patients with and without Bio/BT introduction, and multivariate logistic regression analysis was performed to determine the association of the 4 definitions with treatment needs for Bio/BT.ResultsPatients who were introduced to Bio/BT had heightened C-CS, heavier smoking history, and a greater prevalence of diabetes mellitus than those without (p < 0.05). Poor asthma control (ACT < 20), frequent exacerbations (≥2/yr), and admissions (≥1/yr) were relevant to the future use of Bio/BT in the multivariate regression analysis. Type 2-related biomarkers including absolute eosinophil counts were higher in patients in the Bio introduction group than in the BT introduction group. Meanwhile, there was no significant difference of the 4 characteristics of severe uncontrolled asthma definition between patients in the Bio and those in the BT groups.ConclusionAlthough multiple factors such as treatment cost and asthma phenotypes affect treatment decision-making, the definition of poor asthma control, frequent exacerbations and admission by the ERS/ATS guidelines were important factors for an additional intensive treatment for severe uncontrolled asthma.Trial RegistrationUMIN Clinical Trials Registry: UMIN000024734

A double-blind randomised placebo-controlled trial investigating the effects of lesogaberan on the objective cough frequency and capsaicin-evoked coughs in patients with refractory chronic cough.

ObjectiveBaclofen is a centrally acting γ-aminobutyric acid type B (GABAB) receptor agonist which reduces gastro-oesophageal reflux and suppresses the cough reflex; however, central nervous system side-effects limit its use. Lesogaberan is a novel peripherally acting GABAB agonist, but its effects on refractory chronic cough are unknown.DesignWe performed a single-centre, placebo-controlled, double-blind randomised crossover study in patients with chronic cough, refractory to the treatment of underlying conditions. Patients were randomised to treatment with lesogaberan 120 mg modified release twice daily or matched placebo for 2 weeks and then crossed over to the alternative therapy after a 2-week washout. The primary end-point was 24-h cough frequency measured with an acoustic monitoring system. In addition, cough responses to capsaicin were measured, and gastro-oesophageal reflux assessed by 24-h pH/impedance at screening.Results22 patients were randomised to receive lesogaberan/placebo or placebo/lesogaberan (female (73%); mean±sd age 63.7±7.2 years; median (interquartile range) cough duration 10.5 (5.8–17.0) years; mean (95% CI) 45 (29–67) reflux events in 24 h; two patients had abnormal oesophageal acid exposure times). Although lesogaberan reduced cough counts by 26% over placebo, this did not reach statistical significance (p=0.12). However, lesogaberan did significantly improve cough responses to capsaicin (p=0.04) and the number of cough bouts (p=0.04) compared with placebo. Lesogaberan was well tolerated in this study.ConclusionsLesogaberan improved cough hypersensitivity and the number of bouts of coughing, but not coughs per hour. This implies a possible role for peripheral GABAB receptors in refractory chronic cough.

Effects of treatment with montelukast alone, budesonide/formoterol alone and a combination of both in cough variant asthma

BackgroundWhether cysteinyl-leukotriene receptor antagonists (LTRAs) have a similar antitussive effect to inhaled corticosteroids and long-acting β2-agonist (ICS/LABA), and that LTRA plus ICS/LABA is superior to LTRAs alone or ICS/LABA alone in treating cough variant asthma (CVA) remain unclear. This study aimed to investigate and compare the efficacy of montelukast alone, budesonide/formoterol alone and the combination of both in the treatment of CVA.MethodsNinety-nine CVA patients were assigned randomly in a 1:1:1 ratio to receive montelukast (M group: 10 mg, once daily), budesonide/formoterol (BF group: 160/4.5 μg, one puff, twice daily), or montelukast plus budesonide/formoterol (MBF group) for 8 weeks. The primary outcomes were changes in the cough visual analogue scale (VAS) score, daytime cough symptom score (CSS) and night-time CSS, and the secondary outcomes comprised changes in cough reflex sensitivity (CRS), the percentage of sputum eosinophils (sputum Eos%) and fractional exhaled nitric oxide (FeNO). CRS was presented with the lowest concentration of capsaicin that induced at least 5 coughs (C5). The repeated measure was used in data analysis.ResultsThe median cough VAS score (median from 6.0 to 2.0 in the M group, 5.0 to 1.0 in the BF group and 6.0 to 1.0 in the MBF group, all p < 0.001), daytime CSS (all p < 0.01) and night-time CSS (all p < 0.001) decreased significantly in all three groups after treatment for 8 weeks. Meanwhile, the LogC5 and sputum Eos% improved significantly in all three groups after 8 weeks treatment (all p < 0.05). No significant differences were found in the changes of the VAS score, daytime and night-time CSSs, LogC5 and sputum Eos% among the three groups from baseline to week 8 (all p > 0.05). The BF and MBF groups also showed significant decreases in FeNO after 8 weeks treatment (p = 0.001 and p = 0.008, respectively), while no significant change was found in the M group (p = 0.457). Treatment with MBF for 8 weeks significantly improved the FEV1/FVC as well as the MMEF% pred and decreased the blood Eos% (all p < 0.05).ConclusionsMontelukast alone, budesonide/formoterol alone and a combination of both were effective in improving cough symptom, decreasing cough reflex sensitivity and alleviating eosinophilic airway inflammation in patients with CVA, and the antitussive effect and anti-eosinophilic airway inflammation were similar.Trial registration ClinicalTrials.gov, number NCT01404013.

Comparison of Intravenous Lignocaine and Esmolol in Attenuating Hemodynamic Response and Cough Reflex during Extubation in Hypertensive Patients under General Anaesthesia

Tracheal extubation carries higher complication rates compared to intubation during general anaesthesia (GA). Thus, various drugs are used to attenuate hemodynamic responses and cough reflex during extubation. We investigated if intravenous (IV) lignocaine and esmolol, given prior extubation, was able to achieve that in hypertensive patients under GA. In this prospective, double-blinded, randomised controlled study, 68 hypertensive patients on treatment undergoing GA were analysed. Group L received IV lignocaine 1 mg/kg while Group E received IV esmolol 1.5 mg/kg, 2 minutes before extubation. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) were recorded at the following interval: before study drug administration (T-0), prior extubation (T-1), 1 minute (T-2), 3 minutes (T-3), 5 minutes (T-4) and 10 minutes (T-5) post-extubation. Group L showed significantly increase in HR at T-2 while SBP and MAP increased significantly from T-1 until T-5. Group E showed a significant reduction in HR at T-1 up to T-5 and significantly lower HR at T-1 and T-2 compared to Group L. Group E showed stable SBP, DBP and MAP at all intervals. In conclusion, IV esmolol at 1.5 mg/kg was able to attenuate the hemodynamic response more pronounced when compared to IV lignocaine at 1 mg/kg from extubation stress in patients with hypertension on treatment. Both lignocaine and esmolol were equally effective in suppressing cough reflex during extubation.

Can Ultrasound-Guided Regional Anesthesia Techniques For Tracheostomy Be An Alternative To General Anesthesia?

Introduction The cervical plexus block (CPB) has been used for a long time for both analgesia and anesthesia in carotid endarterectomy and thyroid operations. To be unfamiliar with the technique and its perceived difficulty, potential risks, and possible adverse effects such as intravascular injection has limited broader use before the practical use of ultrasound. We hypothesize that the cervical plexus block can provide adequate anesthesia in tracheostomy cases and provide excellent anesthesia comfort when combined with a translaryngeal block. Methods This double-blinded, randomized 29 patients undergoing primary tracheostomy operation to receive either CPB (Group S) or CPB with translaryngeal block (Group ST). The primary outcome was cumulated analgesic consumption during the first 24 postoperative hours. Secondary outcomes were as follows: pain related to incision, patient tolerance as assessed by tracheostomy cannula comfort score, cough and gag, pain at rest, nausea and vomiting, and time to first analgesic demand. Results The patient tolerance for tracheostomy was higher in Group ST than Group S. The median tracheostomy cannula comfort score was 4.0 in Group S. In contrast, the median score was significantly lower in group ST (P<.001). The cough and gag reflex scores were significantly lower in Group ST than Group S (1.0 vs 4.0, P<.001). Conclusion This trial supported the hypothesis that the CPB combined with the translaryngeal block yields excellent anesthesia for tracheostomies. The technique we briefly described, in a way, is the equivalent of awake fiberoptic intubation to awake tracheostomy with minimal sedation adjusted according to airway patency.

The role of neuronal excitation and inhibition in the pre-Bötzinger complex on the cough reflex in the cat.

Brainstem respiratory neuronal network significantly contributes to cough motor pattern generation. Neuronal populations in the pre-Bötzinger complex (PreBötC) represent a substantial component for respiratory rhythmogenesis. We studied the role of PreBötC neuronal excitation and inhibition on mechanically induced tracheobronchial cough in 15 spontaneously breathing, pentobarbital anesthetized adult cats (35 mg/kg, iv initially). Neuronal excitation by unilateral microinjection of glutamate analog d,l-homocysteic acid resulted in mild reduction of cough abdominal electromyogram (EMG) amplitudes and very limited temporal changes of cough compared with effects on breathing (very high respiratory rate, high amplitude inspiratory bursts with a short inspiratory phase, and tonic inspiratory motor component). Mean arterial blood pressure temporarily decreased. Blocking glutamate-related neuronal excitation by bilateral microinjections of nonspecific glutamate receptor antagonist kynurenic acid reduced cough inspiratory and expiratory EMG amplitude and shortened most cough temporal characteristics similarly to breathing temporal characteristics. Respiratory rate decreased and blood pressure temporarily increased. Limiting active neuronal inhibition by unilateral and bilateral microinjections of GABAA receptor antagonist gabazine resulted in lower cough number, reduced expiratory cough efforts, and prolongation of cough temporal features and breathing phases (with lower respiratory rate). The PreBötC is important for cough motor pattern generation. Excitatory glutamatergic neurotransmission in the PreBötC is involved in control of cough intensity and patterning. GABAA receptor-related inhibition in the PreBötC strongly affects breathing and coughing phase durations in the same manner, as well as cough expiratory efforts. In conclusion, differences in effects on cough and breathing are consistent with separate control of these behaviors.NEW & NOTEWORTHY This study is the first to explore the role of the inspiratory rhythm and pattern generator, the pre-Bötzinger complex (PreBötC), in cough motor pattern formation. In the PreBötC, excitatory glutamatergic neurotransmission affects cough intensity and patterning but not rhythm, and GABAA receptor-related inhibition affects coughing and breathing phase durations similarly to each other. Our data show that the PreBötC is important for cough motor pattern generation, but cough rhythmogenesis appears to be controlled elsewhere.

Airway stent placement for direct cricothyroid membrane puncture anesthesia with airway stricture or fistula.

Tracheal stent implantation with bronchoscope has become one of the main methods for the treatment of airway stenosis. Bronchoscopy is usually performed under local or general anesthesia. The aim of this study is to report our experience with direct cricothyroid membrane puncture anesthesia for airway stent placement. The medical records of 48 consecutive patients who underwent direct cricothyroid membrane puncture anesthesia for tracheal or bronchial stent placement were reviewed. The puncture site was chosen as the interspace between the thyroid cartilage and cricoid cartilage. Through the cricothyroid membrane, lidocaine was injected into the trachea to suppress the cough reflex. The airway stent was placed fluoroscopically at 48 patients at the trachea or bronchus. The success rate and complications of cricothyroid membrane puncture anesthesia were assessed. Anesthesia was successfully performed in all 48 patients. Six patients needed 2-4 mL supplementary lidocaine by injection from the catheter or stent delivery system. Technical success of the stent insertion was achieved in all 48 cases. Small asymptomatic subcutaneous hemorrhage occurred at the puncture site in two patients, which disappeared 1 or 2 days after stent placement. Direct cricothyroid membrane puncture anesthesia for airway metal stent insertion is safe and effective.

Prostaglandin E2 sensitizes the cough reflex centrally via EP3 receptor-dependent activation of NaV 1.8 channels

BackgroundCough hypersensitivity is a major characteristic feature associated with several types of cough, including chronic cough, but its underlying mechanisms remain to be fully understood. Inflammatory mediators, such as prostaglandin E2 (PGE2), have been implicated in both peripheral induction and sensitization of the cough reflex. In this study, using a conscious guinea pig model of cough, we investigated whether PGE2 can sensitize the cough reflex via central actions and, if so, via which mechanisms.MethodsAll drugs were administered by intracerebroventricular (i.c.v.) route and whole-body plethysmograph set-up was used for both induction, using aerosolized citric acid (0.2 M), and recording of cough. Immunohistochemistry was performed to confirm the expression of NaV 1.8 channels in the nucleus tractus solitarius (nTS).ResultsWe show that both PGE2 and the non-selective EP1/EP3 agonist, sulprostone, dose-dependently enhanced the citric acid-induced cough (P ≤ 0.001, P ≤ 0.01, respectively). Pretreatment with the EP1 antagonist, ONO-8130, did not affect the sulprostone-induced cough sensitization, whilst the EP3 antagonist, L-798,106, dose-dependently inhibited this effect (P ≤ 0.05). Furthermore, treatment with either the EP2 agonist, butaprost or the EP4 agonist, L-902,688, had no effect on cough sensitization. Additionally, pretreatment with either the TRPV1 antagonist, JNJ-17203212 or the TRPA1 antagonist, HC-030031, alone or in combination, nor with the NaV 1.1, 1.2, 1.3, 1.4, 1.6 and 1.7 channel blocker, tetrodotoxin, had any effect on the cough. In contrast, pretreatment with the NaV 1.8 antagonist, A-803467, dose-dependently inhibited this effect (P ≤ 0.05). Furthermore, NaV 1.8 channels were shown to be expressed in the nTS.ConclusionCollectively, our findings show that PGE2 sensitizes the cough reflex centrally via EP3 receptor-dependent activation of NaV 1.8 but independently of TRPV1,TRPA1 and TTX-sensitive sodium channel activation. These results indicate that PGE2 plays an important role in central sensitization of the cough reflex and suggest that central EP3 receptors and/or NaVv 1.8 channels may represent novel antitussive molecular targets.Graphical

Follow Your Nose: A Key Clue to Understanding and Treating COVID-19.

This paper suggests that ATP release induced by the SARS-CoV-2 virus plays a key role in the genesis of the major symptoms and complications of COVID-19. Infection of specific cells which contain the Angiotensin-Converting Enzyme 2 (ACE2) receptor results in a loss of protection of the Mineralocorticoid Receptor (MR). Local activation by cortisol stimulates the release of ATP initially into the basolateral compartment and then by lysosomal exocytosis from the cell surface. This then acts on adjacent cells. In the nose ATP acts as a nociceptive stimulus which results in anosmia. It is suggested that a similar paracrine mechanism is responsible for the loss of taste. In the lung ATP release from type 2 alveolar cells produces the non-productive cough by acting on purinergic receptors on adjacent neuroepithelial cells and activating, via the vagus, the cough reflex. Infection of endothelial cells results in the exocytosis of WeibelPalade bodies. These contain the Von Willebrand Factor responsible for micro-clotting and angiopoietin-2 which increases vascular permeability and plays a key role in the Acute Respiratory Distress Syndrome. To test this hypothesis this paper reports proof of concept studies in which MR blockade using spironolactone and low dose dexamethasone (SpiDex) was given to PCR-confirmed COVID-19 patients. In 80 patients with moderate to severe respiratory failure 40 were given SpiDex and 40 conventional treatment with high dose dexamethasone (HiDex). There was 1 death in the HiDex group and none in the SpiDex. As judged by clinical, biochemical and radiological parameters there were clear statistically significant benefits of SpiDex in comparison to HiDex. A further 20 outpatients with COVID-19 were given SpiDex. There was no control group and the aim was to demonstrate safety. No adverse effects were noted and no patient became hyperkalaemic. 90% were asymptomatic at 10 days. The very positive results suggest that blockade of the MR can produce major benefit in COVID19 patients. Further larger controlled studies of inpatients and outpatients are required not only for SARS-CoV-2 infection per se but also to determine if this treatment affects the incidence of Long COVID.

Experience in the use of modern methods of general anesthesia in gynecological operations

Of all the types of pain relief that are currently widespread, the generally accepted is superficial or even analgesic anesthesia, which became possible in connection with the introduction of muscle relaxants into practice. The latter, by relaxing the muscles, create favorable conditions for the operation with a minimum supply of the narcotic substance. At the same time, depression of respiration, cardiac activity, function (liver, kidney and other complications have become very rare. Rapid awakening of patients contributes to the early restoration of the cough reflex, deep breathing and is the best type of prevention of pulmonary complications.

P9‐24: Hydrogen sulfide in serum or sputum supernatant as a biomarker for cough reflex sensitivity in patients with asthma

P9‐24: Hydrogen sulfide in serum or sputum supernatant as a biomarker for cough reflex sensitivity in patients with asthma

Cough. The place of herbal medicine in treatment

Cough is one of the auxiliary mechanisms for cleaning the airways from mucus, foreign particles, microorganisms. The physiological cough reflex allows the mechanism of airway cleansing, provided that mucociliary clearance works sufficiently. However, sometimes the cough loses its protective function, becomes persistent, and impairs the quality of life of the patient. In this regard, in the treatment of cough, attention is paid to both secretomotor and secretolytic therapy. Medicinal plants are among the drugs with such properties. Numerous group of drugs containing herbal components has a reflex action, which allows coping most effectively with cough in the initial stages of diseases accompanied by respiratory symptoms. The most common among them and widely used are plantain leaf, coltsfoot leaf, thermopsis herb, ipecacuanha root, marshmallow root, licorice root, anise fruit, thyme (thyme) herb extract, ivy leaf extract. A well-known drug, the active ingredient of which is ivy leaf extract. Its mechanism of action consists in increasing the production of surfactant and increasing the number of β2-adrenoreceptors on the surface of alveolar cells of the bronchial tree, to which ivy active substance α-hederin is attached, which has a bronchospasmodic and expectorant action. Numerous clinical studies have proven a high efficacy and safety of the product based on ivy leaf extract, which allows us to recommend it as the drug of choice for symptomatic cough therapy in both children and adults during acute respiratory infections.

Influence of intrathoracic vagotomy on the cough reflex in the anesthetized cat

Recurrent laryngeal afferent fibers are primarily responsible for cough in response to mechanical or chemical stimulation of the upper trachea and larynx in the guinea pig. Lower airway slowly adapting receptors have been proposed to have a permissive effect on the cough reflex. We hypothesized that vagotomy below the recurrent laryngeal nerve branch would depress mechanically or chemically induced cough. In anesthetized, bilaterally thoracotomized, artificially ventilated cats, thoracic vagotomy nearly eliminated cough induced by mechanical stimulation of the intrathoracic airway, significantly depressed mechanically stimulated laryngeal cough, and eliminated capsaicin-induced cough. These results support an important role of lower airway sensory feedback in the production of tracheobronchial and laryngeal cough in the cat. Further, at least some of this feedback is due to excitation from pulmonary volume-sensitive sensory receptors.

Influence of Pharyngeal Anaesthesia on Post-Bronchoscopic Coughing: A Prospective, Single Blinded, Multicentre Trial.

Background: Local anaesthesia of the pharynx (LAP) was introduced in the era of rigid bronchoscopy (which was initially a conscious procedure under local anaesthetic), and continued into the era of flexible bronchoscopy (FB) in order to facilitate introduction of the FB. LAP reduces cough and gagging reflex, but its post-procedural effect is unclear. This prospective multicentre trial evaluated the effect of LAP on coughing intensity/time and patient comfort after FB, and the feasibility of FB under propofol sedation alone, without LAP. Material and methods: FB was performed in 74 consecutive patients under sedation with propofol, either alone (35 patients, 47.3%) or with additional LAP (39 patients, 52.7%). A primary endpoint of post-procedural coughing duration in the first 10 min after awakening was evaluated. A secondary endpoint was the cough frequency, quality and development of coughing in the same period during the 10 min post-procedure. Finally, the ease of undertaking the FB and the patient’s tolerance and safety were evaluated from the point of view of the investigator, the assistant technician and the patient. Results: We observed a trend to a shorter cumulative coughing time of 48.6 s in the group without LAP compared to 82.8 s in the group receiving LAP within the first 10 min after the procedure, although this difference was not significant (p = 0.24). There was no significant difference in the cough frequency, quality, peri-procedural complication rate, nor patient tolerance or safety. FB, including any additional procedure, could be performed equally well with or without LAP in both groups. Conclusions: Our study suggests that undertaking FB under deep sedation without LAP does to affect post-procedural cough duration and frequency. However, further prospective randomised controlled trials are needed to further support this finding.

Cough in Idiopathic Pulmonary Fibrosis

Chronic cough is experienced by most patients with idiopathic pulmonary fibrosis (IPF). It is often the first symptom and is associated with reduced quality of life, increased rates of depression and anxiety, more severe physiological impairment, and disease progression. Although not fully understood, recent gains in understanding the pathophysiology of chronic cough in IPF have been made. The pathophysiology is likely multifactorial and includes alterations in mucous production and clearance, architectural distortion, and increased cough reflex sensitivity, suggesting a role for targeted therapies and multidisciplinary treatment. Modifiable comorbidities can also induce cough in patients with IPF. There is a renewed emphasis on measuring cough in IPF, with clinical trials of novel and repurposed therapies for chronic cough emerging in this population. This review provides an update on the clinical characteristics, pathophysiology, and measurement of chronic cough in patients with IPF and summarizes recent developments in non-pharmacological and pharmacological therapies.

Chemical characteristics and significant antitussive effect of the Erigeron canadensis polyphenolic polysaccharide-protein complex

Ethnopharmacological relevanceErigeron canadensis has been used in traditional medicine to treat a variety of respiratory diseases, including acute upper and lower respiratory tract infections and cough-related asthma. There is as yet no relevant experimental or clinical study in the scientific literature evaluating the efficacy of plants in these disorders. Aim of the studyTo investigate the active ingredients in Erigeron canadensis, a complex isolated from flowering parts of a plant was tested for airway defense reflexes, in particular for cough reflexes and airway reactivity. Both were experimentally induced by a chemical irritant that simulated the inflammatory conditions of their formation. Material and methodsThe polyphenolic polysaccharide-protein (PPP) complex was isolated from the flowering parts of Erigeron canadensis by hot alkaline extraction and a multi-stage purification process. The antitussive activity was confirmed as a decrease in the number of citric acid-induced coughs and the bronchodilator effect was verified as a decrease in specific airway resistance (sRaw) in conscious guinea pigs. ResultsThe dark brown Erigeron complex with a molecular weight of 38,000 g/mol contained phenolics (13.2% wt%), proteins (16.3% wt%), and uronic acids (6.3% wt%). The neutral carbohydrate part of Erigeron consisted mainly of xylose (12.1 wt%), glucose (13.3 wt%), arabinose (24.1 wt%), and galactose (41.0 wt%) residues. Arabinogalactan and 4-OMe-glucuronoxylan have been found to be the major polysaccharides in the Erigeron complex. Using a method of chemically-induced cough reflex and guinea pigs test system the Erigeron complex exhibited statistically significant, the dose-dependent antitussive activity, which was similar to that of the centrally-acting opioid agonist codeine. ConclusionPharmacological tests have revealed a new pharmacodynamic effect of the Erigeron complex, namely an antitussive effect. Its activity was most pronounced in comparison with all previously tested compounds from other medicinal plants and approached the effect of codeine, the most potent antitussive used in clinical practice. The results provide the scientific basis for the application of this herb in traditional medicine.