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Table 1. HRV during spontaneous breathing before intervention in the control vs. experimental groups.

HRV index Group Mean+SD 95% CI P Value Cohen’s d Effect size
Mean HR Experimental 94.6 + 9.3 -8.908 to 0.1206 .1199 0.35 Small
(bpm) Control 90.9 + 11.6
RMSSD Experimental 87.4 + 46.5 -33.884 to 0.8915 .3668 0.38 Small
(ms) Control 73.4 + 23.4
pNN50 Experimental 48.9 + 16.6 -19.669 to -0.2714 0.15 Small
(%) Control 46.4 + 14.7 .4839
SD1 Experimental 61.9 + 33 -11.688 to 12.939 .3668 0.38 Small
(ms) Control 51.9 + 16.6
Experimental 1.212 + 0.11 -42.682 to -17.807 0.23 Small
ApEn .2843
Control 1.237 + 0.1
MSE Experimental 8.17 + 1.22 -42.634 to -17.519 .7376 0.06 Small
area 1_5 Control 8.232 + 0.79
Experimental 0.789 + 0.11 -42.867 to -17.891 0.03 Small
DFAα1 .8766
Control 0.785 + 0.14

Abbreviations: SD, Standard deviation; CI, Confidence interval; pNN50, the percentage of adjacent RR intervals with a
difference of duration greater than 50 ms; RMSSD, root-mean square of differences between adjacent normal RR intervals in
a time interval; SDNN, standard deviation of normal-to-normal RR intervals; LF, low frequency; HF, high frequency; LF/HF,
low frequency/ high frequency ratio; ms, milliseconds; HR, heart rate; SD1, standard deviation of the instantaneous variability
of the beat-to beat heart rate; SD2, standard deviation of long-term continuous RR interval variability; ApEn, Approximate
entropy; SampEnt, Sample Entropy; MSE, Multiscale entropy; DFAα1, Detrended fluctuation analysis alpha 1 scale;
ShannEnt, Shannon entropy; L mean , Mean line of recurrence analysis; L max , Maximum line of recurrence analysis; bpm, beats
per minute; Non-paired Student t test.

Table 2. Cardiorespiratory coherence measurements during spontaneous Figure 1. Consort Flow Diagram
breathing (M1, supine) and during slow breathing exercise (M2, seated) in the
experimental group in the week, 4th week and 8th week after beginning of Assessed for eligibility
1st
slow breathing training followed by effect size through Cohen’s d. (N = 127)

CR-Low Mean ± SD 95% CI P Value Cohen’s d Effect size Randomized (n = 127)
1st week M1 83.7 ± 13.2 1.950 to 14.730 .0291 0.44 Small
M2 76.8 ± 17.8
4th week M1 79 ± 18.5 -20.066 to -6.198 <.0001 0.71 Medium Excluded (n = 52)
• Declined to participate
M2 65.6 ± 18.9 (n = 31)
8th week M1 79 ± 15.5 -25.796 to -11.789 <0.0001 1.08 Large • Dropped out of the
project (n = 8)
M2 59.1 ± 20.9 • artifacts in HRV
CR-Med recordings (n = 13)
1st week M1 11.4 ± 9.6 0.2637 to 7.132 .01 0.33 Small
M2 14.6 ± 9.5
-5
4th week M1 14.6 ± 11.3 -5.426 to 8 .0295 0.36 Small
M2 18.7 ± 11.2
8th week M1 13.7 ± 10.6 -4.492 to 5.133 <.0001 0.85 Medium
M2 22.8 ± 10.7 Experimental Group (n = 42)
CR-High Control Group (n = 33)
1st week M1 4.9 ± 5.1 -0.4653 to 5.975 .0397 0.43 Small
M2 8.5 ± 10.5
4th week M1 6.3 ± 9.8 4.476 to 13.109 <.0001 0.74 Medium
M2 15.6 ± 14.6
8th week M1 7.3 ± 7.5 4.720 to 13.846 <.0001 0.84 Medium
M2 18.1 ± 16.4
Abbreviations: SD, Standard deviation; CI, Confidence interval; CR-Low,
low coherence ratio; CR-Med, mean coherence ratio; CR-High, high
consistency ratio. Paired Student t test.

Zuanazzi Cruz—Slow Breathing Exercise on Heart Rate ALTERNATIVE THERAPIES, JUL/AUG 2020 VOL. 26 NO. 4 17