Peak Power Estimated from 6-minute Walk Distance in Asian Patients with Idiopathic Pulmonary Fibrosis and Chronic Obstructive Pulmonary Disease

Background And Objective: Pulmonary rehabilitation guidelines recommend cycle ergometry training at an intensity that exceeds 60% of peak power (P(peak)) with the aim of achieving a physiologic response. However, many clinicians do not have access to an incremental cycle ergometry test (ICET) to allow prescription of training intensity. No studies have investigated whether the 6MWT can be used to estimate the P(peak) achieved during an ICET in subjects with IPF or in Asian subjects with COPD.

Methods: A total of 90 Japanese subjects (IPF n = 45, COPD n = 45) undertook a 6MWT and a symptom-limited ICET in random order. Anthropometry, quadriceps strength and lung function were measured.

Results: Exercise tests were prematurely terminated in 10 subjects with IPF due to profound oxygen desaturation (SpO(2) < 80%). The ICET elicited higher peak heart rates, dyspnea and leg fatigue in both subject cohorts (all P < 0.01). The magnitude of oxygen desaturation was greater during the 6MWT (P < 0.01). 6MWD was strongly associated with P(peak) (r = 0.80, P < 0.01) in both subject cohorts. In subjects with IPF, the predictive equation that accounted for the greatest proportion of variance in P(peak) included 6MWD and FVC %pred (R(2) = 0.70). In the COPD subjects, 6MWD alone accounted for 64% of the variance in P(peak) and the inclusion of other variables did not increase R(2).

Conclusions: P(peak) can be estimated from the 6MWT in Japanese subjects with IPF and COPD. This may allow individualized prescription of the intensity for cycle-based training based on the 6MWT.