Clinical cough I: the urge-to-cough: a respiratory sensation

Abstract

Cough is generated by a brainstem neural network. Chemical and mechanical stimulation of the airway can elicit a reflex cough and can elicit a cognitive sensation, the urge-to-cough. The sensation of an urge-to-cough is a respiratory-related sensation. The role of the respiratory sensation of an urge-to-cough is to engage behavioral modulation of cough motor action. Respiratory sensations are elicited by a combination of modalities: central neural, chemical, and mechanical. Stimulation of respiratory afferents or changes in respiratory pattern resulting in a cognitive awareness of breathing are mediated by central neural processes that are the cognitive neural basis for respiratory sensations, including the urge-to-cough. It is proposed that the urge-to-cough is a component of the cough motivation-to-action system. The urge-to-cough is induced by stimuli that motivate subjects to protect their airway by coughing. Cough receptor stimulation is gated into suprapontine brain systems. In the proposed cough motivation system, the cough stimulus would produce an urge-to-cough which then matches with the cognitive desire for a response to the urge. If a cough is produced by the motor action system, the descending cognitive drive modulates the brainstem cough neural network. Receptors within the respiratory system provide sensory feedback indicating if the cough occurred, the motor pattern, and the magnitude. The limbic system uses that information to determine if the coughing behavior satisfied the urge. Cough is stopped if the urge-to-cough is satisfied; if the urge has not been satisfied then the urge-to-cough will continue to motivate the central nervous system. The central component within this cough motivation system is the intrinsic brain mechanism which can be activated to start the cycle for motivating a cough, the urge-to-cough. Eliciting a cognitive urge-to-cough is dependent on the integration of respiratory afferent activity, respiratory motor drive, affective state, attention, experience, and learning.