Saving Time for Patients with Moderate to Severe COPD: Endurance Test Speed Set Using Usual and Fast Walk Speeds.

Background: For assessing the effects of interventions on exercise tolerance, the tolerable duration (tlimit) of a high-intensity constant-speed endurance test is recommended. The test intensity is determined by the test speed (stest) which should be individualized to target a tlimit of 3 to 15 minutes. We determined the accuracy of setting the stest to achieve a targeted tlimit of 3 to 15 minutes using the participant's easily measured and non-fatiguing usual (susual) and fast (sfast) walk speeds.
Methods: Participants with COPD were asked to walk at their usual and fast walk speeds to establish their susual and sfast. This required that they walk for less than 1 minute. The individualized stest was calculated from a previously developed equation (0.57 x [sfast - susual]) + susual. Participants then completed a constant-speed endurance test, walking at this calculated stest to intolerance, to determine if the resultant tlimit occurred within 3 to 15 minutes.
Results: Twenty-nine participants (forced expiratory volume in 1 second [FEV1] standard deviation [SD ]=43 [25] %predicted; FEV1 to forced vital capacity [FVC]ratio= 41 [13]%; susual = 57.3 [10.4] meters per minute (m·min-1 ); sfast = 71.7 [10.7] m·min-1) completed the study. During testing, 24 (83%) participants used supplemental oxygen and 16 (55%) used a walking aid. The derived stest was 65.6 [10.3] m·min-1 with the observed tlimit of 6.0 [5.0] minute. Twenty-four of 29 (83 %) endurance tests were within 3 to 15 minutes.
Conclusion: Using the usual and fast walk speeds provides a simple, quick, inexpensive method for clinicians to set an acceptable endurance walk speed.