Effects of breathing frequency on the heart rate deceleration capacity and heart rate acceleration capacity.

Purpose: The deceleration capacity (DC) and acceleration capacity (AC) of heart rate as well as the respiratory rate predict outcome after acute myocardial infarction. We evaluated the relation between breathing frequency and both DC and AC, as well as the difference between them.

Methods: We studied fourteen healthy young adults who breathed spontaneously and controlled their breathing to rates of 0.1, 0.2, 0.3, and 0.4 Hz in a supine position. A 5-min R-R interval time series without movement artifacts or ectopic beats was obtained from each studied period and scanned to identify the anchor points that were characterized by a value longer or shorter than the preceding value. Averaged changes of R-R intervals surrounding the deceleration and acceleration anchors were calculated as DC and AC, respectively.

Results: The magnitudes of DC and AC increased progressively as breathing frequency decreased (Both p < 0.001 by one-way repeated-measures analysis of variance). The magnitude of DC was larger than the magnitude of AC during 0.1-Hz breathing (95 % confidence interval of their difference: 1.7-9.7 ms), while the difference between them reduced to near zero at higher frequencies.

Conclusions: Slow breathing enhances the magnitudes of DC and AC simultaneously under the conditions used in this study. The increase in the magnitude of DC is significantly greater than that of AC.