Reliability, Validity, and Responsiveness of a 2-Min Walk Test To Assess Exercise Capacity of COPD Patients: Methods
2MWT: This test was administered according to the protocol as described by Guyatt et al. Subjects were asked to walk as far as they could in 2 min, back and forth along an indoor premeasured corridor of 30 m. Subjects were allowed to rest during the 2-min time period, and no encouragement was given during the test. Immediately before and after the walk test, arterial oxygen saturation (Sao2) and heart rate (HR) were measured by pulse oximetry (Oxypleth; Novametrix; Wallingford, CT), the rating of perceived dyspnea (RPD) and rating of perceived exertion (RPE) were measured by modified Borg scales, and the respiratory rate (RR) was also monitored. No talking was permitted during the tests. The distance walked (in meters) was recorded.
To control for learning and practice effects, the subjects were allowed to become familiar with the test by undertaking a practice walk 1 day prior to the actual testing day. In conducting the actual testing, each subject was asked to perform three 2MWTs with adequate rest of about 20 min between tests. All parameters (ie, Sao2, HR, RPD, RPE, and RR) had to return to baseline levels before the patient commenced another trial. The longest distance walked was used for the analysis of validity and responsiveness. comments
6MWT: The test was conducted according to the ATS guidelines. Subjects were asked to walk back and forth at their own pace along a corridor, attempting to cover as much ground as possible in 6 min. Subjects were permitted to slow down, to stop, and to rest as necessary but were instructed to resume walking as soon as possible. Standard phrases of encouragement were given every minute during the test. The distance walked was recorded in meters. Two trials were performed with adequate recovery between them, and the longest distance walked was used for analysis. Parameters including Sao2, HR, RPD, RPE, and RR were monitored before and immediately after the test.
CPET: A symptom-limited maximal exercise test was performed by the patient under the supervision of a pulmonologist and a qualified nurse. A standardized ramp exercise protocol was conducted using a calibrated, electronically braked cycle ergometer (model CPE/DCE; Medical Graphics Corp) according to the ATS/American College of Chest Physicians guidelines. Functional and metabolic data were measured at rest and during the test. Mixed-expired gas data, minute ventilation, breathing pattern, oxygen uptake, carbon dioxide production, and respiratory exchange ratio were generated at 30-s intervals. Sao2 and HR were monitored continuously with a pulse oximeter, and were recorded every minute.