Article Sections

Introduction

Cough is generally classified as acute, subacute, or chronic based on duration:

  • Acute:  <3 weeks.
  • Subacute:  3-8 weeks.
  • Chronic:  >8 weeks (adults) or >4 weeks (children).

Acutely, cough is predominantly caused by respiratory tract infection (eg, viral upper respiratory infection, bronchitis, community-acquired pneumonia).  Subacutely, most cases represent a postinfectious cough.  In contrast, chronic cough has a much wider range of causes including airway disease, acid reflux, and other conditions discussed below.

Pathogenesis

Chronic cough arises from prolonged activation of the cough reflex due to a persistent irritant or neural hypersensitivity caused by repeated mucosal trauma from coughing itself (ie, vicious cycle).

Cough reflex

The cough reflex consists of 3 elements:

  • Afferent (sensory) arc:  Cough is stimulated by vagus sensory branches that innervate the larynx, airway mucosa, and lung parenchyma.  The glossopharyngeal (pharynx) and trigeminal (paranasal sinuses) nerves also contribute but to a lesser extent.  There are 2 major sensory fiber types:

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