What is the meaning of small airways disease?

From the Guidelines

Small airways disease refers to a condition where the bronchioles, the smallest air passages in the lungs, become inflamed, narrowed, or damaged, leading to airflow obstruction and breathing difficulties, as noted in the diagnosis of bronchiolitis 1. This condition can occur as part of several respiratory conditions, including asthma, chronic obstructive pulmonary disease (COPD), bronchiolitis, and bronchiectasis.

• Symptoms typically include shortness of breath, wheezing, chronic cough, and recurrent respiratory infections.
• Diagnosis of small airways disease requires a comprehensive medical history, physical examination, physiologic testing, and radiographic studies, such as high-resolution CT (HRCT) scans with expiratory cuts, as the resolution of HRCT scanning is limited to airways that are > 2 mm in diameter 1.
• Direct signs of abnormal bronchioles include dilation or airway wall thickening, which often appears with nodular branching of 2 to 4 mm and linear branching “tree-in-bud” abnormalities, while indirect features such as air-trapping (mosaic attenuation on expiration scans) or subsegmental atelectasis may also be present 1.
• Treatment depends on the underlying cause but often includes bronchodilators and inhaled corticosteroids to reduce inflammation and open airways, with the goal of improving morbidity, mortality, and quality of life.
• The standard approach to managing small airways disease involves a stepwise approach, starting with bronchodilators like albuterol, and adding inhaled corticosteroids as needed, with dosing and treatment guided by symptoms and lung function, as the primary goal is to minimize symptoms and prevent disease progression, thus improving quality of life and reducing morbidity and mortality.

From the Research

Definition of Small Airways Disease

• Small airways disease refers to a group of lung diseases that affect the small airways, which may arise primarily within the small airways or secondarily from diseases primarily affecting the bronchi or lung parenchyma 2.
• The term encompasses a wide variety of diseases, including those related to tobacco, mineral dusts, and other exposures, as well as diseases involving other areas of the lung with secondary bronchiolar involvement 2.

Characteristics of Small Airways Disease

• Small airways diseases often exhibit nonspecific histologic features, making diagnosis challenging 2.
• Conditions such as diffuse idiopathic neuroendocrine cell hyperplasia and diffuse panbronchiolitis may show relatively specific diagnostic features histologically 2.
• Clinical and radiologic correlation is important for obtaining the best possible diagnosis 2.

Relationship to Other Respiratory Conditions

• Small airways disease is an important therapeutic target in the treatment of asthma and chronic obstructive pulmonary disease (COPD) 3.
• The pathophysiology of asthma and COPD involves not only the proximal large airways but also the distal small airways 3.
• Significant small airways dysfunction has been found prior to any overt airway obstruction being detectable by conventional spirometry techniques 4.

Diagnosis and Treatment

• Conventional pulmonary function tests may not detect extensive disease in the small airways 3.
• Recent advances in imaging technologies have led to better spatial resolution to assess small airways morphology non-invasively 3.
• New physiological tests have been developed to detect disease and response to therapy in regional airways 3.
• Improving the efficiency of existing aerosolized therapy to direct drug to the appropriate lung regions may improve clinical efficacy 3.