Development of a Measuring Protocol for Inspiratory Muscle Endurance and Pilot Feasibility Study on Inspiratory Muscle Training in Patients Performing Cardiovascular Rehabilitation

Background: Breathlessness and exercise limitation are cardinal manifestations of many cardiovascular diseases (CVD), associated with reductions in quality of life (QoL) and functional capacity. Exercise and inspiratory muscle training (IMT) improve functional capacity in CVD. IM capacity is commonly assessed by maximal inspiratory pressure (MIP). We developed and examined a ramp protocol to measure IM endurance with and without IMT.
Methods: Nineteen subjects were included and allocated to four different groups. Five participants performed adjunct IMT to the cardiac rehabilitation (CR) programme (IMT+EX), four participants performed CR without adjunct IMT (EX only). Five participants performed isolated IMT (IMT only) and five participants were controls. IMT consisted of 2x30 breaths daily at approximately 40% of MIP for 6-12 weeks. MIP, peak pressure and mean and peak power of the ramp protocol were evaluated.
Results: Between group comparisons showed largest improvements for MIP (p = 0.012 compared to control), endurance peak pressure (p = <0.001), endurance mean power (p = <0.001), and endurance peak power (p = <0.001) in the IMT+EX group. Smaller improvements were found for endurance peak load in the IMT only group (p = 0.050 compared to control) and endurance peak power in the EX only group (p = 0.049).
Conclusions: Home-based IMT as adjunct to CR resulted in largest improvements in IM function. Improvement in mean power of an incremental endurance testing protocol were much larger than in MIP after IMT and are likely to better represent improved respiratory function during exercise and activities of daily living.