Cough: what's in a name?

Area of Science:

• Respiratory Physiology
• Neuroscience

Background:

• The cough reflex (CR) and expiration reflex (ER) are key defensive mechanisms of the respiratory tract, primarily triggered by airway irritation.
• While both reflexes protect the airways, they have distinct functions: CR prepares for expulsion, and ER prevents aspiration.

Purpose of the Study:

• To differentiate the cough reflex (CR) and expiration reflex (ER), highlighting their unique physiological and pharmacological properties.
• To address the common practice of conflating CR and ER in research and clinical assessments of cough.
• To review current methodologies for measuring and evaluating cough, emphasizing their importance in airway disease management.

Main Methods:

• Comparative analysis of the sensory pathways, central neural circuits, and physiological/pharmacological modulations of CR and ER.
• Review of existing literature and methodologies for cough assessment.
• Discussion of the clinical relevance of distinguishing between CR and ER in cough events.

Main Results:

• CR and ER possess distinct neural pathways, central processing, and responses to pharmacological agents.
• Cough events are often a complex interplay of both CR and ER, termed a cough bout.
• Current cough assessment methods frequently overlook the distinct characteristics of CR and ER, focusing mainly on expiratory effort frequency.

Conclusions:

• Differentiating between the cough reflex and expiration reflex is essential for a comprehensive understanding of airway defense mechanisms.
• Accurate assessment of cough requires methods that can distinguish between CR and ER and evaluate various aspects beyond mere frequency.
• Improved understanding and measurement of these reflexes can lead to better diagnosis and treatment strategies for airway diseases.