Page 75 - BH-2-4

Brain & Heart Automatic cardiac autonomic modulation assessment

where AMo is the mode amplitude (the percentage of considered statistically significant. The Pearson correlation
intervals corresponding to the mode value relative to the was used to evaluate the relationships between selected
sample size), Mo is the mode, and MxDMn represents the quantitative variables, with a correlation considered strong
degree of interval variability, calculated from the difference if R > 0.7.
between the maximum (Mx) and minimum (Mn) intervals.
According to Baevsky, BSTRi values are considered normal 3. Results
at rest when they range from 80 to 150 conventional units
and are 1.5–2 times higher during physical or emotional 3.1. Population
stress. High BSTRi values suggest reduced variability and The demographics of the 105 healthy participants are
increased sympathetic cardiac activation. 43,44 In Kubios, summarized in Table 1.
BSTRi values are expressed as the square root of the
original Baevsky values. 40 3.2. Linear and NL HRV parameters
To calculate both PNSi and SNSi, each parameter is 3.2.1. Variations in HRV parameters based on short-
first compared to the normal population values reported term interval duration
by Nunan. These values are then scaled using the SD Compared to those calculated from 5-min intervals,
41
of the normal population and refined with undisclosed the average values of most HRV parameters were not
proprietary weighting factors to ensure robust and reliable significantly different when calculated from 2-min intervals
index values. This process considers the relationships across all examined situations (daily activity, NREM
between exercise intensity, heart rate, and HRV. 40 sleep, and acute psychophysiological stress). Significant

2.3. Statistical analysis differences (P < 0.05) for 5-min intervals were found only
for certain recurrence plot parameters (in all conditions),
Data were input into SPSS (21.0 version, Chicago, Illinois) approximated entropy (not under stress), the triangular
for quantitative analysis. All data were examined for index, TINN (during NREM sleep), and minimum heart
expected ranges, outliers, and abnormal values. Continuous rate under stress (Table 2).
variables are presented as mean and SD. Differences
between groups were assessed using either parametric For clarity, only a selection of Kubios-calculated
or non-parametric tests, as appropriate. A P < 0.05 was parameters will be presented in the following tables.

Table 2. Difference in each HRV parameter calculated from short‑term time segments of 2 and 5 min, during regular daily
activity (104 cases), NREM sleep (104 cases), and high‑stress tactical training (16 police officers)
Daily activity NREM sleep High stress
2 min interval 5 min n P 2 min interval 5 min interval n P 2 min interval 5 min interval n P
Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD
MeanRR ms 734.3 120.1 731.9 116.8 104 977.8 148.7 975.0 154.0 104 438.0 75.0 445.3 70.2 16
SDNN ms 31.7 15.1 31.2 13.7 104 27.2 12.5 27.5 12.2 104 13.7 13.1 15.0 12.6 16
MeanHR bpm 83.8 13.2 84.0 13.0 104 62.7 9.1 63.0 9.9 104 140.2 20.2 137.3 17.7 16
MinHR bpm 74.7 11.5 72.7 10.9 104 59.6 8.6 59.1 9.2 104 122.9 20.9 106.6 16.8 16 #
MaxHR bpm 93.7 14.5 97.0 14.9 104 65.7 9.7 67.4 11.6 104 155.6 18.6 160.1 17.7 16
RMSSD ms 22.3 12.1 21.8 11.0 104 32.7 16.0 32.7 16.1 104 6.4 6.1 7.0 6.5 16
pNN50 5.1 8.5 4.6 7.7 104 14.1 16.5 14.2 16.5 104 0.4 1.2 0.6 1.8 16
HRVtriang index 7.6 2.6 8.3 3.0 104 7.1 2.4 7.8 2.8 104 # 3.6 2.3 3.5 2.5 16
TINN ms 140.9 65.0 155.9 67.7 104 117.3 52.2 135.4 62.2 104 # 63.9 57.2 84.3 59.7 16
DC ms 18.3 12.4 17.6 11.5 104 28.0 18.6 27.9 17.9 104 5.4 9.6 5.2 8.6 16
DCmod ms 23.1 12.3 22.5 11.4 104 36.8 18.6 36.7 18.6 104 6.5 7.4 6.8 8.0 16
AC ms −18.1 12.7 −17.5 11.9 104 −28.9 18.3 −28.9 18.1 104 −4.2 6.0 −4.3 5.8 16
ACmod ms −23.7 14.0 −23.0 12.8 104 −38.7 19.9 −38.6 20.0 104 −5.8 5.6 −6.3 6.6 16
VLFpow FFT ms 2 98.6 130.7 99.4 102.8 104 39.0 60.4 45.5 58.3 104 25.0 29.3 25.7 27.0 16
LFpow FFT ms 2 880.4 1,051.9 844.5 921.3 104 250.1 364.3 286.3 397.6 104 276.6 504.1 317.2 596.6 16
(Contd...)

Volume 2 Issue 4 (2024) 4 doi: 10.36922/bh.3503