The Effects of Obesity on Lung Physiology, the Prevalence and Severity of Chronic Pulmonary Diseases, and Inhalation Treatment

Eleonore Fröhlich1,2 1Center for Medical Research, Medical University of Graz, Graz, Austria; 2Research Center Pharmaceutical Engineering GmbH, Graz, AustriaCorrespondence: Eleonore Fröhlich, Center for Medical Research, Medical University of Graz, Graz, 8010, Austria, Tel +43-316-3857-3011, Email [email protected]: Obesity itself induces macroscopic, microscopic, and functional changes in the lungs, potentially making obese individuals more susceptible to acute and chronic pulmonary diseases. Apart from direct contribution to the course of the disease, obesity-induced alterations of the respiratory tract may influence the delivery and efficacy of inhaled formulations. The review examined obesity-induced changes in healthy lungs and the link between obesity and the prevalence and severity of chronic respiratory diseases. Fat accumulation at the tissue and cellular levels, as well as an increased thickness of the smooth muscle layer and an increase in the extracellular matrix, caused a reduction in lung compliance, resistance, reactance, and lung volumes. Conversely, airway hyperreactivity and closure increased, and ventilation/perfusion mismatch was observed. Changes in deposition, metabolization, and permeation across the respiratory barrier in obese lungs may alter the availability of inhaled drugs. Obesity-induced lung alterations may in part explain the higher reported doses of the bronchodilators and anticholinergics in obese compared to normal-weight asthma patients. Based on the observed changes, formulations with smaller particle sizes that require lower airflow may be more effective for obese patients with obstructive lung diseases. Keywords: lung morphology, lung function, drug bioavailability, asthma, COPD, cystic fibrosis