Phase-dependent changes of HRV TD and NL parameters during HUT
| RMSSD | PNN50 | SD1 | SD2 | |||||
|---|---|---|---|---|---|---|---|---|
| Group 1 | Group 2 | Group 1 | Group 2 | Group 1 | Group 2 | Group 1 | Group 2 | |
| Phase 1 | 39.5±20.6 | 47.3±29.6 | 11.7±15.9 | 22.2±20.4 | 28.0±14.6 | 33.5±21.0 | 44.1±22.1 | 54.0±29.3 |
| Phase 2 | 29.1±15.7 | 28.2±12.5 | 9.6±11.8 | 8.2±9.0 | 20.6±11.1 | 20.0±8.8 | 47.7±21.1 | 48.9±20.4 |
| Phase 3 | 24.9±12.5 | 27.9±13.5 | 6.6±9.4 | 8.0±9.1 | 17.7±8.8 | 19.8±9.5 | 41.1±19.4 | 48.8±21.8 |
| p (phase 1 vs 2) | 0.003 | <0.001 | 0.004 | <0.001 | 0.003 | <0.001 | NS | NS |
| p (phase 2 vs 3) | 0.004 | NS | 0.005 | NS | 0.004 | NS | 0.032 | NS |
HRV, heart rate variability; HUT, head-up tilt testing; NL, non linear; NS, not significant; TD, time domain.