Target dyspnea ratings predict expected oxygen consumption as well as target heart rate values

Abstract

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 approximately 75% of maximal oxygen consumption (V 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 V 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 V O2 of 0.76 +/- 0.29 L/min (p = 0.18 for V O2 between groups). Compared with the expected V O2 from Visit 1, the individual percent differences in V 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 V 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 V O2 were similar for the two groups at Visits 2 (p = 0.38) and 3 (p = 0.27). There were no significant differences for V 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 (approximately 75% of V O2max) for 10 min of submaximal exertion.