Dynamic Respiratory Muscle Function in Late-Onset Pompe Disease

For ILC testing, a commercially available, spring-loaded device provided a pressure load to inspiration that is independent of inspiratory flow. The patient had to generate enough threshold inspiratory pressure in order to receive airflow. The tension of the spring was adjusted to regulate the threshold pressure of the imposed load. Volume, flow and timing responses were evaluated to an inspiratory threshold load equivalent to 40% of PImax.

Endurance was evaluated by identifying the time limit (Tlim) that a participant could maintain ventilation while breathing with a submaximal inspiratory threshold load. The test begin after a one-hour rest. After reaching a steady state breathing pattern (e.g. stable tidal volumes for >30 seconds), a threshold inspiratory load equivalent to 40% of PIMAX was placed on the inspiratory port of the mouthpiece. During the loaded breathing condition, the respiratory rate was set to each subject's self-selected resting breathing rate. The perceived exertion was monitored, and subjects received encouragement to maintain the target rate and mouth pressure. Encouragement was provided to maintain the established breathing pattern and to continue to task failure. The test ended when the subject could not open the threshold valve for three consecutive breaths.

For ILC testing, a commercially available, spring-loaded device provided a pressure load to inspiration that is independent of inspiratory flow. The patient had to generate enough threshold inspiratory pressure in order to receive airflow. The tension of the spring was adjusted to regulate the threshold pressure of the imposed load. Volume, flow and timing responses were evaluated to an inspiratory threshold load equivalent to 40% of PImax.

For ILC testing, a commercially available, spring-loaded device provided a pressure load to inspiration that is independent of inspiratory flow. The patient had to generate enough threshold inspiratory pressure in order to receive airflow. The tension of the spring was adjusted to regulate the threshold pressure of the imposed load. Volume, flow and timing responses were evaluated to an inspiratory threshold load equivalent to 40% of PImax.

Chest wall and diaphragmatic motions was measured in three planes with dynamic magnetic resonance imaging (MRI). The cradio-caudal change in diaphragm excursion between full inspiration and full expiration (representing diaphragm descent) was measured in the frontal plane. The anterior-posterior change in the area of the right and left sides of the chest cavity was measured in the sagittal plane (representing chest expansion). Diaphragm and chest excursion was recorded dynamically during 30-second periods of resting breathing and deep breathing.