Chronic cough of lower airways may be due to- cough variant asthma (CVA), nonasthmatic eosinophilic bronchitis (NAEB), atopic cough etc. Correct assessment of the cause is a must to induce proper management to the patient. certain investigations like- Spirometry, bronchial challenge test, induced sputum test, and fractional exhaled nitric oxide help in assessing the chronic cough associated with lower airways disease. 

further investigations that one may need are- Chest CT and bronchoscopy, after ruling out the common cause.

CVA is best treated with- Inhaled corticosteroids alone or corticosteroids plus beta-2 agonists or leukotriene receptor antagonists, NAEB requires corticosteroids for its management, and atopic cough resolves with the use of corticosteroids or antihistamine drugs.

Source: Lai K., Zhan W., Zhan C. (2021) Lower Airways: Assessment and Treatment for Cough. In: Cho S.H., Song WJ. (eds) Diagnosis and Treatment of Chronic Cough. Springer, Singapore. https://doi.org/10.1007/978-981-33-4029-9_5