Effect of the trajectory of exertional breathlessness on symptom recall and anticipation: A randomized controlled trial

Background: Breathlessness is a major cause of physical limitation. Recalled breathlessness intensity may differ from experienced intensity and be influenced by the intensity trajectory including the ‘peak-end rule’. The primary aim was to test if adding two minutes of low intensity exercise at the end of an exercise test would change the recalled breathlessness. Secondary aims included to analyse the impact of the peak and end exertional breathlessness intensity on breathlessness recall. Methods: Randomized controlled trial of 92 adults referred for exercise testing who were randomized (1:1), at test end, to 2 minutes of additional low intensity exercise (intervention; n = 47) or stopping at peak exertion (control; n = 45). Experienced breathlessness during the test and recalled intensity (30 min after the test) was assessed using the Borg CR10 scale. Results: Participants were aged a mean 59 years; 61% men; 79% reported a mMRC ≥1. There was no between-group difference in recalled breathlessness intensity, 5.51 ([95% CI] 5.00 to 6.01) vs. 5.73 (5.27 to 6.20; p = 0.52) in controls, even though the intervention group had a significantly lower end breathlessness (mean difference 0.96; 0.24 to 1.67; p = 0.009). Recalled exertional breathlessness was most strongly related to peak breathlessness (r2 = 0.43). When analyzed together, end breathlessness did not add any explanatory value above that of peak breathlessness. Conclusion: Adding an episode of two minutes of lower exercise and breathlessness intensity at the end of an exercise test did not affect symptom recall, which was most strongly related to peak breathlessness intensity. Trial registration: ClinicalTrials.gov (NCT03468205).