Table 2.
HRV values
| HRV index | GAE | GSta | P-value |
|---|---|---|---|
| Time domain | |||
| Mean RRi, ms | 721.6±106.9 | 736.8±133.5 | 0.72 |
| STD RRi, ms | 19.3±6.5 | 14.3±12.5 | 0.007 |
| RMSSD, ms | 17.8±5.6 | 11.7±9.5 | 0.008 |
| RRi tri | 5.2±1.7 | 4.0±3.0 | 0.01 |
| TINN, ms | 88.7±26.9 | 70.6±62.2 | 0.01 |
| Frequency domain | |||
| LF, ms2 | 203.0±210.7 | 101.8±169.7 | 0.01 |
| HF, ms2 | 111.3±74.9 | 45.6±80.7 | 0.002 |
| LF/HF | 2.5±2.1 | 2.3±2.0 | 0.6 |
| Non-linear analysis | |||
| SD1 | 12.7±3.9 | 8.3±6.7 | 0.007 |
| SD2 | 30.4±14.8 | 16.2±12.5 | <0.001 |
| ApEn | 0.9±0.07 | 1.0±0.06 | 0.002 |
| SampEn | 1.4±0.32 | 1.7±0.3 | 0.007 |
Abbreviations: HRV, heart rate variability; RRi, R-wave peak detection intervals; STD RRi, standard deviation of RRi; RMSSD, root mean square of successive differences; RRi tri, triangular index; TINN, triangular interpolation of RRi; LF, low frequency; HF, high frequency; SD1, beat-to-beat variability; SD2, standard deviation of long-term variability; ApEn, approximate entropy; SampEn, sample entropy; GAE, acute exacerbation COPD group; GSta, stable COPD group.