Background: One of the contributors to exercise limitation in COPD is dynamic hyperinflation. Although dynamic hyperinflation appears to occur during several exercise protocols in COPD and seems to increase with increasing disease severity, it is unknown whether dynamic hyperinflation occurs at different severity stages according to the Global initiative for chronic Obstructive Lung Disease (GOLD) in daily life. The present study, therefore, aimed to compare dynamic hyperinflation between COPD GOLD stages II-IV during daily activities.
Methods: Thirty-two clinically stable patients with COPD GOLD II (n = 10), III (n = 12), and IV (n = 10) participated in this study. Respiratory physiology during a daily activity was measured at patients' homes with Oxycon Mobile. Inspiratory capacity maneuvers were performed at rest, at 2-min intervals during the activity, and at the end of the activity. Change in inspiratory capacity is commonly used to reflect change in end-expiratory lung volume (DeltaEELV) and, therefore, dynamic hyperinflation. The combination of static and dynamic hyperinflation was reflected by inspiratory reserve volume (IRV) during the activity.
Results: Overall, increase in EELV occurred in GOLD II-IV without significant difference between the groups. There was a tendency for a smaller DeltaEELV in GOLD IV. DeltaEELV was inversely related to static hyperinflation. IRV during the daily activity was related to the level of airflow obstruction.
Conclusions: Dynamic hyperinflation occurs independent of GOLD stage during real-life daily activities. The combination of static and dynamic hyperinflation, however, increases with increasing airflow obstruction.