Airway Irritation and Cough in Young People: Perspective

Preethi Tyagi^*
*Correspondence: Preethi Tyagi, Department of Pulmonary Medicine, University of Utah Health, USA, Email:

Perspective

Cough hypersensitivity is the most common symptom of chronic cough, which is a complex condition that affects adults. Coughing is a natural defence mechanism that protects the airways from aspiration, infection, and irritation. When the cough response is disturbed, however, it becomes an illness. Chronic cough is a significant source of morbidity, particularly in terms of quality of life and daily activities. Treatment Emergent Adverse Events (TEAEs) include dyspnea, wheezing, bronchospasm, oropharyngeal discomfort, hoarseness, voice alteration, dysgeusia, and cough caused by irritation or inflammation in the respiratory system after oral inhalation of Active Pharmaceutical Ingredients (APIs) and excipients. These TEAEs are crucial to consider during the clinical development of inhaled medication products because they can cause poor adherence, cessation, and, ultimately, treatment failure. Coughing is a 'reflex event' that starts with the activation of vagal afferent sensory nerves in both extrapulmonary and pulmonary locations. Afferent impulses are sent from the sensory nerves to the cough centre in the brain stem and pons. The cough centre generates an efferent signal after processing, which leads to an 'appropriate' motor response.

Because of the immaturity of their biological systems and higher air consumption per body weight than adults, young children are thought to be more exposed to environmental triggers. However, it is hypothesized that early childhood exposure to an irritant/pollutant may raise the future risk of respiratory issues, including persistent cough. The mechanisms by which environmental influences cause chronic cough are not entirely understood, although experimental research can help infer some of them. Transient receptor potential channels are abundant in sensory nerve terminals and may play a role in the effects of environmental triggers. The Transient Receptor Potential Ankyrin-1 (TRPA1) channel, in particular, may play a role in irritant-induced cough because it is activated by a variety of irritants, including isothiocyanate, acrolein, and cinnamaldehyde, all of which are found in air pollutants and cigarette smoke and may sense cellular oxidative stress.

Unmyelinated C-fibers make up the majority of the bronchopulmonary vagal afferent nerves. Only awake subjects cough when C-fiber nociceptors terminate in and around the mucosal surface of the pulmonary airways. They are susceptible to inflammatory mediators and irritants that activate or sensitise nociceptor nerve terminals. Smaller aerosols that deposit more distally, away from the trachea and more proximal airway, have been found to elicit a stronger cough response.

After exposure to e cigarettes, airway irritation, mucus hypersecretion, and an inflammatory response, including systemic changes, have been identified, leading to an increase in respiratory symptoms as well as changes in respiratory function and host defence mechanisms. In people with asthma, cystic fibrosis, and chronic obstructive pulmonary disease, using an e-cigarette has been related to an increase in symptoms. The growth in e-cigarette experimentation among never-smokers, particularly children and teenagers, is a major public health concern, as it leads to nicotine addiction and increases the likelihood of becoming a traditional smoker over time.

The sensation of irritation that precedes the motor act of coughing, the so-called Urge to Cough (UTC) sensation, which in turn drives the cough, has recently gotten a lot of attention. Initially, it was thought that cough could only be caused by a neuronal network in the brainstem. Cough can also be triggered by pharyngeal stimulation, implying that pharyngeal sensory nerves are involved in the development of the cough reflex associated with URTI. The cough reflex, as well as a cognitive sensation known as the UTC, can be elicited by chemical and mechanical stimulation of the airway. The ability to detect the UTC is critical for maintaining proper airway protection. As a result, it's been assumed that URTI-related cough is primarily evoked through the voluntary pathway, such as cognitive recognition of the need to cough to protect airways. Mucosal inflammation causes upper airway irritative impulses to reach the cerebral cortex, eliciting cough under voluntary control. The cerebral reaction to pharyngeal afferent information is crucial because tussigenic stimuli raise the UTC [1-5].

Irritative stimuli acting on reflexogenic regions of the pharyngeal mucosa might elicit acute cough from Upper Respiratory Tract Infection (URTI) and other external detriments. Inflammatory mediators acting on upper airway sensory terminations and intensifying the UTC sensation may be responsible for URTIrelated cough. The UTC is generated when information from the pharynx is encoded into a conscious knowledge of airway irritations, which in turn may promote behavioural or induced coughing to clear the airways. Irritative stimuli acting on reflexogenic sections of the pharyngeal mucosa sustain acute cough caused by URTI or other exogenous noxious agents, which in turn evoke the UTC, a sense of irritation that precedes the motor act of coughing. This sort of cough can be intensified, reduced, or inhibited consciously at varying levels of behavioural control, although it is difficult to effectively suppress it during a URTI by mere willpower alone. Cough remains an unmet clinical need despite massive scientific efforts. However, nonpharmacological features such as sensory impact and placebo effect play a large role in cough drug efficacy for URTI-associated cough.

References

1. Jo, Eun-Jung, and Woo-Jung Song. "Environmental triggers for chronic cough." Asia Pac Allergy 9 (2019).

Google Scholar, Crossref, Indexed at

2. Mukae, Hiroshi, Takeshi Kaneko, Yasushi Obase, and Masaharu Shinkai, et al. "The Japanese respiratory society guidelines for the management of cough and sputum (digest edition)." Respir Investig 59 (2021): 270-290.

Google Scholar, Crossref , Indexed at

3. Cheng, Meng-Yu, Wen-Hsin Hsih, Mao-Wang Ho, and Yi-Chyi Lai, et al. "Younger adults with mild-to-moderate COVID-19 exhibited more prevalent olfactory dysfunction in Taiwan." J Microbiol Immunol Infect 54 (2021): 794-800.

Google Scholar, Crossref , Indexed at

4. Murgia, Vitalia, Sara Manti, Amelia Licari, and Maria De Filippo, et al. "Upper respiratory tract infection-associated acute cough and the urge to cough: New insights for clinical practice. " Pediatr Allergy Immunol 33 (2020): 3-11.

Google Scholar, Crossref, Indexed at

5. Edwards, Earlroy. "Principles of suctioning in infants, children and young people." Nurs Child Young People 33 (2021).

Google Scholar, Crossref, Indexed at