RESUMEN
PURPOSE: The aim of this study is to compare the respiration-stabilizing abilities of audio coaching (AC) and AC with visual feedback (VF) with that of free breathing (FB). MATERIALS AND METHODS: Ten healthy volunteers were told to breathe in FB, under AC and under AC + VF in random order. The standard deviation (SD) values of the respiratory cycle, the amplitude, the lowest points (exhalation), and the highest points (inhalation) of respiratory wave were used as indices of respiratory stability. RESULTS: Compared with FB, the AC method significantly improved respiratory cycle stability (p = 0.001). The AC + VF method improved the stability of the respiratory cycle, the amplitude and the lowest point of respiratory wave (all p < 0.001). In analyses of each subject's data, compared with FB, the AC method significantly improved the respiratory cycle stability in five subjects, and the AC + VF method improved the stability of the respiratory cycle, the amplitude and the lowest point of respiratory wave in 4, 5, and 4 subjects, respectively. In two cases, coaching did not improve respiratory stability. CONCLUSION: The AC + VF method had the most beneficial effects on respiratory stability. However, coaching is not necessarily effective in all cases. Therefore, the most suitable method should be chosen on an individual basis.