Effect of Inspiratory muscle training in hypercapnic chronic obstructive pulmonary disease patients during acute care: a randomised clinical trial

Weakness of respiratory muscles along with respiratory failure is a common finding in chronic obstructive pulmonary disease (COPD) patients which leads to dyspnoea and hence decreased functional capacity. Despite a sound theoretical rationale regarding the potential role of inspiratory muscles, the role of inspiratory muscle training (IMT) along with the conventional non-invasive ventilation (NIV) on important clinical outcomes has not been investigated in these patients during acute care. 34 hypercapnic stable COPD patients were randomly allocated to one of the interventions that lasted for 10 days: IMT with NIV (n=17), and NIV alone (n=17). IMT was administered 2 times in a day (15 min each time) by threshold loading at an intensity starting from 30% and progressed to 60% of their maximal inspiratory effort (PImax). NIV was given at an optimal pressure titrated for each patient for at least >8 h per day. Outcome measures (respiratory muscle strength, respiratory failure, dyspnoea, and functional capacity) were assessed before and after 10 days of intervention. Clinical characteristics and outcome variables of patients were similar between the groups at baseline. Addition of IMT led to a significantly greater increase in respiratory muscle strength (P=0.01), reduction in dyspnea (modified medical research council dyspnea scale, P=0.001); improved outcomes of respiratory failure (PaCO2, P=0.03; PaO2, P=0.002) and improved functional capacity (6 min walk distance, P=0.001) as compared to NIV alone. A short duration IMT program in addition to NIV was found to be effective in improving respiratory muscle strength, perception of dyspnoea, functional capacity and respiratory failure in hypercapnic COPD patients.