Table 2.
Heart rate variability indices during the first and the third sustained or intermittent hypoxia sessions.
| Sustained hypoxia | Intermittent hypoxia | ANOVA | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Session |
Baseline normoxia |
Middle hypoxia |
End hypoxia |
Recovery normoxia |
Baseline normoxia |
Middle hypoxia |
End hypoxia |
Recovery normoxia |
Condition main effect |
Condition x time interaction |
Condition x session interaction |
|
| SDNN (ms) | S1 | 81.7 (38.6) | 80.5 (61.4) | 87.7 (50.6) | 105.7 (50.8) | 84.9 (30.3) | 97.5 (35.5) | 107.2 (24.7) | 102.6 (43.7) | p < 0.001 | p = 0.002 | p = 0.100 |
| S3 | 89.0 (37.1) | 63.5 (31.0) | 75.8 (25.2) | 99.5 (35.5) | 99.6 (35.7) | 113.5 (40.6) | 118.1 (34.1) | 117.0 (59.6) | ||||
| PNN50 (%) | S1 | 41.0 (27.4) | 28.1 (22.0) | 29.0 (20.9) | 40.0 (20.3) | 48.4 (22.7) | 38.6 (22.6) | 35.0 (18.5) | 49.7 (19.4) | p = 0.011 | p = 0.362 | p = 0.783 |
| S3 | 45.0 (21.9) | 25.2 (20.5) | 23.9 (13.5) | 38.3 (21.8) | 49.7 (21.9) | 39.0 (23.6) | 36.8 (20.7) | 46.4 (18.7) | ||||
| RMSSD (ms) | S1 | 85.8 (67.7) | 70.9 (69.0) | 69.6 (67.9) | 92.5 (71.3) | 98.5 (54.2) | 80.2 (60.9) | 70.4 (44.4) | 97.03 (61.5) | p = 0.010 | p = 0.638 | p = 0.156 |
| S3 | 90.0 (48.3) | 59.3 (40.2) | 56.2 (23.5) | 83.3 (54.8) | 116.3 (61.5) | 95.3 (75.2) | 83.3 (49.7) | 106.7 (66.1) | ||||
| LF (u.n.) | S1 | 27.1 (19.2) | 29.8 (17.0) | 32.6 (16.1) | 37.7 (20.6) | 25.2 (14.7) | 24.6 (14.5) | 28.4 (22.8) | 27.6 (16.9) | p = 0.167 | p = 0.115 | p = 0.478 |
| S3 | 23.4 (14.3) | 31.8 (6.4) | 33.2 (13.3) | 28.1 (15.4) | 26.7 (19.7) | 22.9 (13.4) | 25.7 (11.6) | 32.4 (18.4) | ||||
| HF (u.n.) | S1 | 43.9 (23.5) | 35.6 (21.9) | 25.7 (19.0) | 27.2 (16.6) | 45.5 (16.9) | 30.61 (22.7) | 23.4 (16.9) | 40.4 (21.5) | p = 0.180 | p = 0.123 | p = 0.407 |
| S3 | 43.7 (21.2) | 34.7 (20.1) | 24.1 (11.3) | 29.1 (14.9) | 49.3 (24.9) | 34.3 (20.4) | 29.0 (19.6) | 37.0 (19.7) | ||||
| LF/HF | S1 | 0.97 (1.23) | 1.82 (2.70) | 2.23 (1.77) | 1.99 (1.62) | 0.70 (0.56) | 1.59 (1.86) | 1.08 (0.69) | 1.37 (1.77) | p = 0.658 | p = 0.231 | p = 0.239 |
| S3 | 0.80 (0.77) | 1.65 (1.38) | 1.69 (0.92) | 1.22 (0.74) | 1.85 (4.77) | 1.04 (0.86) | 1.85 (2.23) | 1.75 (2.42) | ||||
Values are provided for the normoxic phases before and after hypoxic exposure and in the middle and the end of the hypoxic exposure. Data are means (SD); SDNN, standard deviation of R–R interval; PNN50, percentage of successive R–R that varied by 50 ms or more; RMSSD, root-mean-square difference of successive normal R–R intervals; LF, low frequency in normalized units; HF, high frequency in normalized units; S1, first session; S3, third session.