Mechanistic study of inspiratory training in childhood Asthma: Rationale and methods of a pediatric clinical trial.

Asthma is a common pediatric disease of the airways. Obesity among children increases the risk of asthma and is associated with a unique non-allergic asthma phenotype that is highly symptomatic and often unresponsive to conventional drugs. However, the mechanisms linking obesity with incident asthma, more frequent and severe symptoms, and resistance to conventional drugs remain unknown. Excess fat on the chest wall and abdomen forces children with obesity to breathe at lower lung volumes where small airway dysfunction is more likely to occur and where the normal length-tension relationship of the diaphragm is suboptimal; this leads to altered breathing mechanics and inspiratory muscle fatigue, which could lead to exertional dyspnea. While inspiratory training (IT) increases inspiratory muscle strength and endurance, improves exercise tolerance, and reduces exertional dyspnea, most research has focused on adults. The Mechanistic Study of Inspiratory Training in Childhood Asthma (MICA) study is designed with 2 objectives: (1) compare measures of small airway dysfunction and inspiratory muscle functioning between obese (