- Updated on July 31, 2019
J Assoc Physicians India. 2000 Mar; vol 48(no. 3): p. 343-345.
The role of cough and hyperventilation in perpetuating airway inflammation in asthma.
Singh V, Chowdhary R, Chowdhary N.
Department of Pulmonary Medicine, SMS Medical College, Jaipur-302 016, India.
Air flowing through a pipe exerts frictional stress on the walls of the pipe. Frictional stress of more than 40 N/m2 (velocity equivalent of air 113 m/s) is known to cause acute endothelial damage in blood vessels. The frictional stress in airways during coughing may be much greater, however, since the velocity of air may be as high as speed of sound in air. We suggest that high levels of frictional stress perpetuate airway inflammation in airways which are already inflamed and vulnerable to frictional stress-induced trauma in patients with asthma. Activities associated with rapid ventilation and higher frictional stress (e.g. exercise, hyperventilation, coughing, sneezing and laughing) cause asthma to worsen whilst activities that reduce frictional stress (Yoga ‘Pranayama’, breathing a helium-oxygen mixture and nasal continuous positive airway pressure) are beneficial. Therefore control of cough may have anti-inflammatory benefits in patients with asthma.
Respir Physiol Neurobiol. 2007 Jun 15; 156(3): p. 331-339.
Cough and ventilatory adjustments evoked by aerosolised capsaicin and distilled water (fog) in man.
Lavorini F, Pantaleo T, Geri P, Mutolo D, Pistolesi M, Fontana GA.
Dipartimento di Area Critica Medico Chirurgica, Unit Funzionale di Medicina Respiratoria, Universite di Firenze, Viale G.B. Morgagni 85, 50134 Firenze, Italy.
Airway receptors mediate cough and ventilatory adjustments. Simultaneous assessment of cough sensory-motor components and changes in breathing pattern may provide insights into the receptors prevailingly stimulated by inhaled irritants. Nineteen subjects inhaled capsaicin and fog up to threshold concentrations for cough. Cough intensity, respiratory sensations and changes in breathing pattern induced by the two irritants were compared. Capsaicin and fog cough threshold values did not correlate. Coughing induced by both agents was preceded by qualitatively similar sensations and by significant increases in minute ventilation and respiratory drive due to selective increases in tidal volume (P<0.01). Cough intensity was similar with both agents. Cough frequency and the intensity of the urge to cough were higher with capsaicin (P<0.01). The lack of correlation between fog and capsaicin cough threshold values suggests differences in the neural mechanisms activated. The selective increase in tidal volume suggests prevailing involvement of rapidly adapting receptors. The stronger sensations evoked by capsaicin may contribute to the higher cough frequency observed with this agent.
Monaldi Arch Chest Dis. 1999 Jun;54(3):275-9.
Advances in understanding and treatment of cough.
Sherrington School of Physiology, St. Thomas’ Hospital Campus (UMDS), London, UK.
Many different conditions and diseases cause cough. The commonest acute causes are pollution, including cigarette smoke, and upper respiratory tract infection. The commonest chronic causes are postnasal drip, asthma, chronic bronchitis and gastro-oesophageal reflux. Epidemiological studies give widely different patterns of incidence. The different conditions that cause cough have in common the fact that the cough is mediated via the vagus nerves, with sensory receptors in and under the epithelium from the larynx down to the smaller bronchi. These receptors are polymodal, responding to a large variety of stimuli, including mechanical and chemical irritants, inflammatory mediators, intraluminal material and large volume changes of the lungs. With irritation and inflammation, C fibre receptors release neurokinins such as substance P, which in turn stimulate cough receptors. The central nervous pathways for the cough reflex are poorly understood. They can be activated or inhibited voluntarily. Studies on the pharmacology of the central nervous pathways of coughing are opening up new therapeutic possibilities. Other new therapies include drugs acting on the sensory receptors for cough, thereby avoiding adverse central nervous effects.
Pulm Pharmacol Ther. 2007;20(4):416-22.
The problem of cough and development of novel antitussives.
Department of Thoracic Medicine, National Heart and Lung Institute, Dovehouse Street, London SW3 6LY, UK. email@example.com
Cough is a very common clinical symptom and current therapies are largely ineffective, indicating a major unmet medial need. There is a pressing need to develop novel and safe antitussive therapies. This is likely to arise from better understanding of the sensory nerves involved in cough and the signalling pathways that are activated. A major therapeutic target should be sensitization of the cough reflex which is a feature of patients with both acute (virally induced) cough and chronic cough, including chronic idiopathic cough. Studies on human cough mechanisms are limited. There are several novel therapeutic approaches that are currently being explored. Perhaps the most promising drugs are transient receptor potential vanilloid-1 (TRPV(1)) antagonists, selective cannabinoid agonists (CB2 agonists), maxi-K channel openers and P2X3 antagonists. New cough therapies may target airway nerve sensitization and may best be delivered as inhalers to minimize any systemic effects. Understanding the intercellular signalling pathways involved in nociception may lead to novel drugs, such as p38 mitogen-activated protein (MAP) kinase inhibitors, being used in the treatment of cough in the future. It is also likely that several novel treatments that are developed as analgesics will also prove to be beneficial in the treatment of cough.