The relationship between heart rate and VO2 in moderate-to-severe asthmatics.

Objective: The main purpose of this study was to evaluate whether the %HRR-%VO2R relationship and %HRR-VO2peak relationship are affected in patients with moderate or severe asthma and whether airway obstruction and aerobic capacity influence these relationships.Methods: A linear regression was calculated using the paired %VO2R-%HRR and %VO2peak-%HRR for 93 subjects with asthma. The mean slope and y-intercept were calculated and compared with the line of identity (y-intercept = 0, slope = 1) for all patients and subgroups for the following conditions: low and normal VO2peak and low and normal FEV1.Results: The slope and intercepts of %VO2R-%HRR were similar to the line of identity for all groups (p > 0.05), and the regressions between %HRR and %VO2peak did not coincide with the line of identity for all groups (p < 0.05). There were no associations between the intercepts of the %HRR-VO2peak and the %HRR-%VO2R relationship with the VO2peak (p > 0.05) or FEV1 (p > 0.05).Conclusions: This is the first study to confirm a constant equivalence between %HRR and %VO2R in outpatients with moderate or severe asthma. Our data also suggest that the relationship between %HRR and %VO2peak is unreliable. These results support the use of %HRR in relation to %VO2R to estimate exercise intensity in this population, independently of the pulmonary function and fitness level.