Breathlessness rating type influences respiratory behavior during hypercapnia in the rebreathing test

Objective The online rating of perceived breathlessness in a rebreathing test (RT) is a new and powerful technique to analyze the psychological and physiological process related to the mechanisms of breathlessness. The aim of the present study was to assess the influence of rating type on respiratory sensation and behavior during repeated hypercapnic exposures. Methods Sixty-one healthy women performed three rebreathing trials. Half of them were auditorily cued to rate breathlessness intensity every 12 s (CR, n =30), the other half was instructed to rate breathlessness each time a change in breathlessness intensity was perceived (UCR, n =31). The ventilatory response was assessed simultaneously. Results The CR group yielded an earlier threshold in tidal volume ( V T ) than the UCR group. Only in the UCR group did changes occur across rebreathing trials: the V T threshold decreased, the respiratory rate (RR) threshold increased, and the sensitivity of the RR increased. Conclusions The type of breathlessness rating influences respiratory behavior in the RT. The short-interval cued rating seems to be the best option for a standardized application of this test in research on panic disorder.