Audio-Visual Biofeedback for Respiratory Motion Management: Comparison of the Reproducibility of Breath-Holding between Visual and Audio Guidance

Purpose: To compare the reproducibility of breath-holding and comfort between two biofeedback guidance methods (audio and visual) in a respiratory monitoring system. Method and Materials: An audio-feedback respiratory monitoring device, which was modified from a visual-feedback self-respiration monitoring system (Abches, APEX Medical Inc., Tokyo, Japan) previously developed by the authors’ group, was constructed. Twenty patients (13 men, 7 women; mean age, 68.5 years; range, 54 - 85 years) with tumors in the thorax or abdominal region were enrolled in the present study. Computed tomography images were acquired from all patients three times using the two (i.e., audio and visual) respiration monitoring devices. To evaluate the reproducibility of breath-holding, the distance between an anatomical landmark and the tumor position was measured. Furthermore, patients were asked which guidance method they preferred (visual or audio) for comfortable breath-holding. Results: The two guidance methods improved the reproducibility of breath-holding compared with free-breathing, and no significant overall differences between two methods were observed (the mean displacements of the landmark-tumor distance were 2.60 ± 1.38 mm and 2.35 ± 1.63 mm, for visual and audio guidance, respectively). In five patients, the magnitude of position displacement in the series of three computed tomography images under audio guidance was twice as large as the other under visual guidance. Audio guidance was preferred to visual guidance by 65% (13 of 20) of the patients. However, the reproducibility of breath-holding did not always correspond with patient preference. Conclusion: There were some individual differences in the reproducibility of the visual and audio guidance methods. More appropriate, individualized guidance methods for each patient would improve the reproducibility of breath-holding in respiratory motion management.