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Utility of Equations to Estimate Peak Oxygen Uptake and Work Rate From a 6-Minute Walk Test in Patients With COPD in a Clinical Setting

Kirkham, Amy A. MSc; Pauhl, Katherine E. MSc, MPT; Elliott, Robyn M. MPT; Scott, Jen A. MPT; Doria, Silvana C. MPT; Davidson, Hanan K. MPT; Neil-Sztramko, Sarah E. MSc; Campbell, Kristin L. BScPT, PhD; Camp, Pat G. BScPT, PhD

Journal of Cardiopulmonary Rehabilitation and Prevention: November/December 2015 - Volume 35 - Issue 6 - p 431–438
doi: 10.1097/HCR.0000000000000129
Pulmonary Rehabilitation
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PURPOSE: To determine the utility of equations that use the 6-minute walk test (6MWT) results to estimate peak oxygen uptake (

o2) and peak work rate with chronic obstructive pulmonary disease (COPD) patients in a clinical setting.

METHODS: This study included a systematic review to identify published equations estimating peak

o2 and peak work rate in watts in COPD patients and a retrospective chart review of data from a hospital-based pulmonary rehabilitation program. The following variables were abstracted from the records of 42 consecutively enrolled COPD patients: measured peak

o2 and peak work rate achieved during a cycle ergometer cardiopulmonary exercise test, 6MWT distance, age, sex, weight, height, forced expiratory volume in 1 second, forced vital capacity, and lung diffusion capacity. Estimated peak

o2 and peak work rate were estimated from 6MWT distance using published equations. The error associated with using estimated peak

o2 or peak work to prescribe aerobic exercise intensities of 60% and 80% was calculated.

RESULTS: Eleven equations from 6 studies were identified. Agreement between estimated and measured values was poor to moderate (intraclass correlation coefficients = 0.11-0.63). The error associated with using estimated peak

o2 or peak work rate to prescribe exercise intensities of 60% and 80% of measured values ranged from mean differences of 12 to 35 and 16 to 47 percentage points, respectively.

CONCLUSIONS: There is poor to moderate agreement between measured peak

o2 and peak work rate and estimations from equations that use 6MWT distance, and the use of the estimated values for prescription of aerobic exercise intensity would result in large error. Equations estimating peak

o2 and peak work rate are of low utility for prescribing exercise intensity in pulmonary rehabilitation programs.

Supplemental Digital Content is Available in the Text.Equations that use the 6-minute walk test to estimate peak oxygen uptake and work rate have poor to moderate agreement with measured values when used in a clinical setting. The use of these equations for prescription of aerobic exercise intensity in pulmonary rehabilitation would result in large errors.

Rehabilitation Sciences Graduate Program (Ms Kirkham, Drs Campbell and Camp), Department of Physical Therapy (Mss Pauhl, Elliott, Scott, and Doria, Mr Davidson, Drs Campbell and Camp), School of Population and Public Health (Ms Neil-Sztramko), and Centre for Heart Lung Innovation (Dr Camp), University of British Columbia, Vancouver, BC, Canada.

Correspondence: Pat G. Camp, BScPT, PhD, Department of Physical Therapy, University of British Columbia, Room 166, 1081 Burrard St, Vancouver, BC, Canada V6Z 1Y6 (pat.camp@hli.ubc.ca).

No conflicts of interest were reported.

Supplemental digital content is available for this article. Direct URL citation appears in the printed text and is provided in the HTML and PDF versions of this article on the journal's Web site (www.jcrpjournal.com).

Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.