Table 2.
Time and frequency domain heart rate variability by sleep stage
| Variable | Fluid Control (n = 16) | Alcohol (n = 16) | p value | |
|---|---|---|---|---|
| N2 | RRI (ms) | 1111 ± 59 | 943 ± 46* | <0.001 |
| Resp. rate (breaths/min) | 14 ± 1 | 15 ± 1* | 0.003 | |
| HF (ms 2 ) | 1270 (461−2024) | 357 (124−2155)* | 0.013 | |
| pNN50 (%) | 46 ± 7 | 25 ± 7* | 0.001 | |
| RMSSD (ms) | 82 ± 11 | 52 ± 10* | 0.001 | |
| SWS | RRI (ms) | 1100 ± 51 | 972 ± 41* | <0.001 |
| Resp. rate (breaths/min) | 15 ± 1 | 16 ± 1* | 0.002 | |
| HF (ms 2 ) | 1429 ± 279 | 698 ± 146* | <0.001 | |
| pNN50 (%) | 47 ± 6 | 29 ± 6* | <0.001 | |
| RMSSD (ms) | 81 ± 9 | 48 ± 6* | <0.001 | |
| REM | RRI (ms) | 1046 ± 57 | 936 ± 50* | <0.001 |
| Resp. rate (breaths/min) | 15 ± 1 | 15 ± 1 | 0.453 | |
| HF (ms 2 ) | 978 (340−1864) | 335 (122−1162)* | 0.004 | |
| pNN50 (%) | 33 ± 7 | 20 ± 6* | 0.004 | |
| RMSSD (ms) | 76 ± 11 | 49 ± 8* | 0.004 |
Results are means ± SEM (normal distribution) or median (25th−75th percentile, non-normal distribution); HF, high frequency; pNN50, proportion of R−R intervals that exceed 50 ms; RMSSD, root mean square of successive differences. *p < 0.05, compared with corresponding fluid control condition.