Table 2.
Comparison of the mean HRV parameters between the study groups.
| Parameter | Control group (n = 26) |
Study group (post-COVID) (n = 65) |
p |
|---|---|---|---|
| Linear parameters in the time domain | |||
| Mean RR [ms] | 1115 (122) | 1162 (111) | 0.093 |
| SDNN [ms] | 129 (30) | 139 (33) | 0.166 |
| RMSSD [ms] | 91 (35) | 90 (39) | 0.857 |
| pNN50 [%] | 41.9 (17.4) | 47.8 (18.4) | 0.109 |
| Frequency domain | |||
| VLF [ms2] | 10,490 (4762) | 13,826 (6600) | 0.022 |
| LF [ms2] | 2879 (1471) | 2889 (1606) | 0.742 |
| HF [ms2] | 3084 (2704) | 3063 (2665) | 0.816 |
| Non-linear analysis | |||
| V0 [%] | 66.5 (18.2) | 49.0 (15.4) | < 0.001 |
| V2 [%] | 7.5 (6.3) | 14.7 (6.9) | < 0.001 |
| Sample entropy | 1.27 (0.20) | 1.32 (0.18) | 0.357 |
| α1 | 0.99 (0.15) | 1.05 (0.16) | 0.082 |
| α2 | 1.03 (0.10) | 1.11 (0.08) | < 0.001 |
| PRSA | |||
| DC [a.u.*] | 26.8 (10.1) | 26.6 (9.9) | 0.878 |
| AC [a.u.] | − 23.9 (7.0) | − 23.1 (7.5) | 0.816 |
| Resp. peak [a.u.] | 4.25 (0.61) | 3.91 (0.56) | 0.012 |
| Resp. range [a.u.] | 0.281 (0.031) | 0.275 (0.030) | 0.425 |
*a.u.- arbitrary units, see details in the “Methods” chapter.