Nonlinear dynamics of heart rate variability during paced breathing: Recurrence quantification analysis of heart rate

Abstract

BackgroundRecurrence is a fundamental property of many physiological systems and recurrence plot (RP) with its subsequent quantitative analysis is an effective approach to assessment complexity of physiological signals. The aim of this study is to assess the influence of paced breathing on RP complexity measures of heart rate variability (HRV) in healthy young females.Materials and methodsTwenty‐nine female university students (age 20.4 ± 0.2 years) participated in the study. The subjects breathed spontaneously and following the respiratory pacer for 5 min at each of 5 frequencies: 6.5, 6, 5.5, 5, 4.5 breaths/min. Five‐minute heart rate variability time series were recorded during spontaneous and paced breathing. We computed the following RQA measures: recurrence rate (REC), mean line length (Lmean), maximum line length (Lmax), determinism (DET), and Shannon entropy of line length distribution (ShanEn). Friedman ANOVA and Wilcoxon test were used to determining the significance of differences between measurements. Data are mean±SE.ResultsPaced breathing causes significant increasing of REC from 22.07±0.71 % (free breathing) to 29.53±0.6 % (6.5 breaths/min) (p <0.01). Paced respiratory rate was associated with significant increasing of Lmean from 8.33±0.2 (free breathing) to 17.54±0.94 (6.5 breaths/min) (p <0.01). Lmax was significantly (p < 0.01) higher during paced breathing (6.5 breaths/min – 279.59±14.8, 6 breaths/min – 297.96±12.27, 5.5 breaths/min – 284.09±17.3, 5 breaths/min – 276.14±22.32, 4.5 breaths/min – 228.15±23.53) than during free breathing (71.18±6.77). The statistical analysis showed that in comparison with free breathing, the DET value was significantly higher during paced breathing (p < 0.01): 96.28±0.18 at free breathing, 96.28±0.18 at 6.5 breaths/min, 98.61±0.09 at 6 breaths/min, 98.65±0.09 at 5.5 breaths/min, 98.69±0.18 at 5 breaths/min, 98.28±0.36 at 4.5 breaths/min. ShanEn was significantly (p < 0.01) increased during paced breathing (6.5 breaths/min – 3.35±0.04, 6 breaths/min – 3.3±0.03, 5.5 breaths/min – 3.22±0.03, 5 breaths/min – 3.24±0.06, 4.5 breaths/min – 3.17±0.06) than during free breathing (2.85±0.03). Recurrence indexes showed that the heart rate dynamics during paced breathing are different from free breathing, suggesting a loss of complexity of the heart rate autonomic regulation system.ConclusionsRecurrence quantification analysis of HRV is sensitive to paced breath and might, therefore, be suited to assess interactions between the cardiovascular system and respiration. The loss of HRV complexity might reflect an increased regularity of HR oscillations caused by paced breathing. Thus, RP has the potential to provide supplementary information about the dynamics in heart rate regulation.Support or Funding InformationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.