A preliminary study into the effect of biofeedback on end tidal carbon dioxide levels during slow breathing in healthy volunteers

Objectives: To investigate the effect of visual biofeedback on end tidal carbon dioxide levels during slow breathing in healthy volunteers. Design: Preliminary study with experimental design in which each participant experienced both conditions i.e. slow breathing with and without visual biofeedback Setting: Human Performance Laboratory, university campus Participants: Fifteen university students. Baseline data and outcome measures: Primary outcome measure was end tidal carbon dioxide (ETCO2); Secondary outcomes were respiratory rate; pulserate; non-invasive oxygen saturations; lung function Results: There was a mean rise in ETCO2 of 0.35 k Pa (CI0.09–0.6) during slow breathing with visual biofeedback, and 0.36 k Pa (CI0.13–0.6) without biofeedback. The use of visual feedback had no observable effect on ETCO2 despite participants successfully reducing their respiratory rate further under this condition (mean 5 breaths per minute with feedback, versus 7 without feedback). ETCO2 and respiratory rate were negatively correlated under both conditions (Pearson’sr = 0.42). Conclusions: In this study of healthy volunteers manipulating respiratory rate was found to result in a significant rise in ETCO2 levels under both conditions, but the use of visual biofeedback had no significant additional effect on ETCO2. Visual biofeedback did have a statistically significant effect on respiratory rate, enabling subjects to achieve lower rates than in the absence of biofeedback. This suggests visual biofeedback may have a role in enabling people to reduce breathing rates, but this needs to be confirmed by larger trials