Review: Exercise Endurance Could Be Key Tool to Track COPD Treatment Response

Improved exercise endurance can be a meaningful way to measure response to treatment in patients with chronic obstructive pulmonary disease (COPD), according to a new review article.

The case for exercise endurance as an important biomarker in COPD rests in its correlation with quality of life, according to corresponding author Richard Casaburi, PhD, MD, of the University of California Los Angeles Medical Center, and colleagues. The authors said exercise endurance is an objective measurement, and it is also closely linked with quality of life since patients with higher endurance tend to be less restricted in their daily activities.

“Therefore, it is an ideal candidate as an outcome for drug development trials,” Casaburi and colleagues wrote. “Unfortunately, no exercise endurance measure is qualified by regulatory authorities for use in trials of [COPD] and no approved COPD therapies have claims of improving exercise endurance.”

In hopes of changing that, Casaburi and colleagues laid out a conceptual framework for the use of exercise endurance in a pre-proof published online by the Journal of the COPD Foundation. The research was done under the auspices of the COPD Biomarker Qualification Consortium, a group created to evaluate biomarkers and outcome measures to aid in drug development.

Specifically, the authors argued that constant work rate cycle ergometry (CWRCE), measured at baseline and then at intervals following treatment, would be an ideal way to see how therapy is affecting patients with COPD. CWRCE involves the use of a stationary cycle ergometer.

Patients are asked to continue cycling as long as they can. In some cases, other physiological and sensory data are simultaneously collected.

“Exercise tolerance limit is reached when the individual is limited by symptoms, unable to maintain pedaling cadence or unable to continue safely,” Casaburi and colleagues wrote. “At exercise cessation, exercise duration is recorded.”

Lower-limb exercises are particularly meaningful in this patient group, the authors said, because lower limbs have greater muscle mass, and due to “the central role of the muscles of ambulation in supporting activities most important to people with COPD.”

The investigators said the use of exercise as a metric also aligns with qualitative research into patient sentiment and experiences. They noted that many patients with COPD report lower rates of physical activity on “bad” symptom days and increased activity on “good” days. Patients also frequently report having to pace themselves on bad days, coming up with strategies to accomplish necessary tasks within the constraints of their illness.

The authors said an improvement in exercise endurance would suggest that patients have also seen improvement in their ability to perform their daily tasks, which is a key goal of COPD therapy.

The authors said the introduction of CWRCE as a drug development tool could help speed the process of testing potential new therapies for COPD and getting successful therapies to market.

“We have demonstrated here that improved exercise endurance time has a direct relationship to an individual with COPD’s experience of physical functioning in daily life, which is a meaningful patient-centered benefit,” Casaburi and colleagues wrote.

They said their future research will focus on assembling a database of endurance times of people with COPD and assessing which particular factors led to changes in those times.

Reference:

Casaburi R, Merrill DD, Harding G, et al. A conceptual framework for use of increased endurance time during constant work rate cycle ergometry as a patient-focused meaningful outcome in COPD clinical trials. Chronic Obstr Pulm Dis. Published online January 10, 2022. doi:10.15326/jcopdf.2021.0258