Page 101 - BH-2-4

Brain & Heart RSA and breathing-specific heart rate

data were reported as means ± 1 standard error of the (12.1% ± 0.4%) and females (12.9% ± 0.5%). The mode
mean and as the coefficient of variation (CV = standard and the median RSA values were slightly lower than the
deviation/mean; %). A two-tailed t-test was used to average (10.4% and 10.9%, respectively).
compare the two groups. Critical values for correlation
coefficients, differences between slopes (b) and intercepts 3.2. Correlations
(a) of the linear function, and differences in mean values 3.2.1. Body weight and height
were considered statistically significant at p < 0.05. Since
each X-Y relationship contained seven data points (with Neither f h nor f resp showed statistically significant
7 – 2 = 5° of freedom), the critical value for statistical correlations with body height or weight, whether males,
significance of the correlation coefficient r (for a two-tailed females, or the combined group were considered. Similarly,
test at α = 0.05) was 0.754, which corresponds to a no significant correlation was found between ΔHR’ and
coefficient of determination (R ) of 0.569. body height or weight.
2
3. Results 3.2.2. Breathing frequency and HR

3.1. Resting values Table 2 presents the intercepts (a) and slopes (b) of
the linear regressions between the cardiorespiratory
Table 1 summarizes the average anthropometric and variables pertinent to RSA and ΔHR’. In all three groups
cardiorespiratory values relevant to RSA.
ΔHR’ was observed in all 635 subjects. On average, Table 2. Respiratory sinus arrhythmia correlations:
ΔHR’ was 8.6 ± 0.3 bpm, which was similar between males Cardiorespiratory variables relevant to respiratory sinus
(8.3 ± 0.3 bpm) and females (8.8 ± 0.3 bpm), but with arrhythmia
considerable variability among subjects (Figure 2), ranging X A b r p
from 1 bpm (observed in one male and one female) to
46 bpm. Normalizing ΔHR’ by the mean f h (ΔHR’ as a All subjects fresp 16.6 −0.57 0.97 <0.001
percentage of f h) did not reduce the variability, because fh 3.1 0.078 0.85 <0.02
ΔHR’ showed no correlation with f h (see below). On HR’trough 13.3 −0.072 0.903 <0.01
average, RSA accounted for 12.6% ± 0.5% of f h, with a CV HR’peak −4.4 0.18 0.996 <0.001
of 60%. This was not significantly different between males fh/fresp 2.2 1.16 0.96 <0.001
3.5 0.98 0.96 <0.001
HR’trough/fresp
Table 1. Respiratory sinus arrhythmia correlations: 0.7 1.34 0.98 <0.001
Anthropometric and cardiorespiratory values HR’peak/fresp
Males fresp 15.9 −0.56 0.98 <0.001
Parameters Males (n=272) Females Combined fh 1.3 0.10 0.86 <0.02
(n=363) (n=635)
HR’trough ns
Age, years 19.5±0.1 (5.1) 19.5±0.1 (4.9) 19.5±0.1 (5.0)
HR’peak −6.5 0.20 0.98 <0.001
Height, cm 177±0.4 (3.8) *164±0.5 (4.9) 170±0.6 (5.9)
fh/fresp 1.8 1.10 0.91 <0.01
Weight, kg 74±0.7 (14.9) *59±0.7 (19.0) 65.4±0.8 (20.4)
HR’trough/fresp 2.7 1.002 0.94 <0.01
fh, bpm 68.6±0.7 (15.6) 69.4±0.7 (15.6) 69.1±0.7 (15.6)
HR’peak/fresp 0.8 1.22 0.95 <0.001
fresp, br/min 13.6±0.3 (30.9) 14±0.2 (27.4) 13.8±0.2 (28.9)
Females fresp 17.4 −0.59 0.94 <0.01
HR’peak, bpm 72.8±0.7 (15.7) 73.8±0.7 (15.4) 73.4±0.7 (15.5)
fh ns
HR’trough, bpm 64.5±0.6 (16.4) 65±0.7 (16.9) 64.8±0.7 (16.7)
HR’trough 14. 8 −0.091 0.957 <0.001
ΔHR’, bpm 8.3±0.3 (61.6) 8.8±0.3 (60.0) 8.6±0.3 (60.6)
HR’peak −1.3 0.14 0.961 <0.001
RSA, % 12.1±0.4 (61.0) 12.9±0.5 (59.7) 12.6±0.5 (60.2)
fh/fresp 2.9 1.16 0.96 <0.001
fh/fresp, beats/ 5.6±0.1 (38.6) 5.4±0.1 (34.3) 5.5±0.1 (36.3)
breath HR’trough/fresp 4.1 0.98 0.94 <0.01
Notes: Values are means±1 standard error of the mean in brackets HR’peak/fresp 0.8 1.43 0.98 <0.001
or the coefficient of variations (CV=standard deviation/mean, Notes: Linear regression Y=a + b·X, where Y is the HR’peak-HR’through
%). fh: Mean heart rate (bpm=beats/min). fresp: Breathing rate difference (ΔHR’), b is the slope of the linear function, and a is the
(br/min=breaths/min). HR’: Instantaneous heart rate (bpm). intercept of the linear function. r: Correlation coefficient. p: Probability
ΔHR’: Peak-trough difference in instantaneous heart rate (bpm). of the null hypothesis (i.e., no correlation at the level indicated) to
RSA: Respiratory sinus arrhythmia expressed in percent of fh (ΔHR’/fh be correct. fresp: Breathing frequency (breaths/min). fh: Heart rate
100). fh/fresp: Breathing-specific heart rate (beats/breath). *Statistically (beats/min). fh/fresp: Breathing-specific heart rate (beats/breath).
significant difference between genders (p<0.001). ns: Not significant (p>0.05). Critical value r for two-tail test=0.754).

Volume X Issue X (2024) 4 doi: 10.36922/bh.3956