Cough in Idiopathic Pulmonary Fibrosis

Abstract

Chronic cough is experienced by most patients with idiopathic pulmonary fibrosis (IPF). It is often the first symptom and is associated with reduced quality of life, increased rates of depression and anxiety, more severe physiological impairment, and disease progression. Although not fully understood, recent gains in understanding the pathophysiology of chronic cough in IPF have been made. The pathophysiology is likely multifactorial and includes alterations in mucous production and clearance, architectural distortion, and increased cough reflex sensitivity, suggesting a role for targeted therapies and multidisciplinary treatment. Modifiable comorbidities can also induce cough in patients with IPF. There is a renewed emphasis on measuring cough in IPF, with clinical trials of novel and repurposed therapies for chronic cough emerging in this population. This review provides an update on the clinical characteristics, pathophysiology, and measurement of chronic cough in patients with IPF and summarizes recent developments in non-pharmacological and pharmacological therapies.

Keywords: cough; idiopathic pulmonary fibrosis; interstitial lung disease; patient reported outcome (PRO) measures; prognosis; quality of life.

Figure 1

Phases of cough. Schematic representation of the changes in airflow (liters per second) and subglottic pressure (centimeter of water) during the phases of cough. Phase 1. The glottis opens on activation of the cough reflex, and a deep breath is inhaled (inspiratory phase). Phase 2. The glottis then closes and expiratory muscles forcibly contract (compressive phase), with a transient increase in intrathoracic pressure. Phase 3. The glottis opens with rapid airflow, causing oscillation of the bronchial tissues (expulsive phase).

Figure 2

The cough reflex. Schematic representation of the afferent and efferent pathways of the cough reflex (further detail in the text). RAR, Rapidly adapting receptors; SAR, slowly adapting stretch receptors [adapted from Mazzone (19) with permission from Elsevier].