OSA and Chronic Respiratory Disease: Mechanisms and Epidemiology

Abstract

Obstructive sleep apnea (OSA) is a highly prevalent disorder that has profound implications on the outcomes of patients with chronic lung disease. The hallmark of OSA is a collapse of the oropharynx resulting in a transient reduction in airflow, large intrathoracic pressure swings, and intermittent hypoxia and hypercapnia. The subsequent cytokine-mediated inflammatory cascade, coupled with tractional lung injury, damages the lungs and may worsen several conditions, including chronic obstructive pulmonary disease, asthma, interstitial lung disease, and pulmonary hypertension. Further complicating this is the sleep fragmentation and deterioration of sleep quality that occurs because of OSA, which can compound the fatigue and physical exhaustion often experienced by patients due to their chronic lung disease. For patients with many pulmonary disorders, the available evidence suggests that the prompt recognition and treatment of sleep-disordered breathing improves their quality of life and may also alter the course of their illness. However, more robust studies are needed to truly understand this relationship and the impacts of confounding comorbidities such as obesity and gastroesophageal reflux disease. Clinicians taking care of patients with chronic pulmonary disease should screen and treat patients for OSA, given the complex bidirectional relationship OSA has with chronic lung disease.

Keywords: hypoventilation; hypoxia; lung inflammation; obstructive; obstructive pulmonary disease; outcomes assessments; sleep apnea.

Figure 1

Pathophysiologic Consequences of Obstructive sleep apnea (OSA): A schematic representation of OSA-driven pathways leading to chronic lung disease. OSA leads to adverse effects through at least three causal pathways (represented by octagons): intermittent hypoxia, intrathoracic pressure swings, and sleep fragmentation (arousals). These lead to several pathophysiologic changes (represented by dashed squares) that may cause clinical events (rounded boxes). Abbreviations: LRTI—Lower respiratory tract infection; HIF—Hypoxia-inducible factor; LV/RV—Left ventricle/Right ventricle; Non-Th2 Asthma Phenotype—A type of asthma characterized by non-allergic, neutrophilic inflammation.