Am. J. Respir. Crit. Care Med., Volume 159, Number 5, May 1999, 1485-1489

Target Dyspnea Ratings Predict Expected Oxygen Consumption as Well as Target Heart Rate Values

ROBERTO MEJIA, JOSEPH WARD, TIMOTHY LENTINE, and DONALD A. MAHLER

Section of Pulmonary and Critical Care Medicine, Department of Medicine, Dartmouth Medical School, Lebanon, New Hampshire; and National Institute of Respiratory Disease, Mexico City, Mexico

A target heart rate (THR) is the traditional method to prescribe and monitor exercise training intensity in healthy individuals. However, patients with chronic obstructive pulmonary disease (COPD) are limited by ventilatory impairment and dyspnea rather than cardiovascular factors. An alternative approach is to use dyspnea ratings as a target for exercise training in patients with respiratory disease just as ratings of perceived exertion have been used in healthy individuals. The study was a randomized, parallel group trial comparing the ability of patients with COPD to accurately and reliably produce an exercise intensity using a target dyspnea rating (TDR) versus a THR. At Visit 1 patients performed an incremental exercise test on the cycle ergometer, and target values were calculated at ~ 75% of maximal oxygen consumption ( O₂). At Visits 2 (3 to 5 d later) and 3 (2 wk later) each patient was instructed to produce a TDR or a THR for 10 min of submaximal exertion. Anthropometric characteristics, lung function, and exercise performance were similar for the 22 patients in each group at Visit 1. For the TDR group the dyspnea target was 2.5 ± 1.5 at an expected O₂ of 0.88 ± 0.28 L/min; for the THR group the heart rate (HR) target was 114 ± 15 beats/min at an expected O₂ of 0.76 ± 0.29 L/min (p = 0.18 for O₂ between groups). Compared with the expected O₂ from Visit 1, the individual percent differences in O₂ at Visit 2 were 3.9 ± 18.1% (TDR) and 0.5 ± 23.2% (THR) (p = 0.58); at Visit 3 the individual percent differences in O₂ were 2.3 ± 17.0% (TDR) and 2.6 ± 30.6% (THR) (p = 0.52). The number of patients < 10% and  10% of the expected O₂ were similar for the two groups at Visits 2 (p = 0.38) and 3 (p = 0.27). There were no significant differences for O₂ values (absolute or individual percent) at Visits 2 and 3 for each group and between the groups (p = 0.79). In conclusion, patients with symptomatic COPD demonstrated a comparable ability to use dyspnea ratings and HR as a target to accurately and reliably produce an expected exercise intensity (~ 75% of O₂max) for 10 min of submaximal exertion.

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