Table 2.
Cerebrovascular and respiratory data during baseline and LBNP in each body position
| Baseline | 20% | 40% | 60% | 80% | 100% | |
|---|---|---|---|---|---|---|
| MCAv (cm/sec) | ||||||
| 45°HUT | 55.2 ± 3.0 | 51.2 ± 3.1a | 50.8 ± 3.0a | 49.9 ± 2.6a | 48.5 ± 3.0a | 45.2 ± 3.2a |
| Supine | 59.8 ± 2.0 | 54.4 ± 2.0a | 55.4 ± 2.6a | 55.8 ± 2.3a | 52.6 ± 2.1a | 49.9 ± 1.6a |
| 45°HDT | 59.3 ± 2.3 | 54.3 ± 2.8a | 54.6 ± 3.0a | 54.3 ± 2.4a | 54.1 ± 2.9a | 53.6 ± 2.6a |
| Body Position: P = 0.077; % Protocol: P < 0.001; Interaction: P = 0.053 | ||||||
| MCAv CVR (mmHg/cm/sec) | ||||||
| 45°HUT | 1.55 ± 0.10b | 1.67 ± 0.11b , a | 1.79 ± 0.11b , a | 1.70 ± 0.10b , a | 1.72 ± 0.10b , a | 1.69 ± 0.11b , a |
| Supine | 1.36 ± 0.09 | 1.50 ± 0.09a | 1.49 ± 0.08a | 1.50 ± 0.09a | 1.56 ± 0.10a | 1.52 ± 0.10a |
| 45°HDT | 1.51 ± 0.08 | 1.60 ± 0.12a | 1.61 ± 0.11a | 1.62 ± 0.10a | 1.62 ± 0.09a | 1.65 ± 0.08a |
| Body Position: P = 0.040; % Protocol: P < 0.001; Interaction: P = 0.970 | ||||||
| PCAv (cm/sec) | ||||||
| 45°HUT | 31.7 ± 2.9 | 29.7 ± 2.9 | 29.8 ± 3.0 | 29.4 ± 2.7a | 28.5 ± 2.7a | 26.3 ± 2.5a |
| Supine | 32.9 ± 2.1 | 29.8 ± 1.9a | 30.5 ± 2.0a | 30.6 ± 2.2a | 29.2 ± 2.0a | 27.9 ± 1.9a |
| 45°HDT | 32.6 ± 2.4 | 30.5 ± 2.4 | 29.9 ± 2.3a | 30.0 ± 2.2a | 30.0 ± 2.2a | 30.0 ± 2.2a , c |
| Body Position: P = 0.583; % Protocol: P < 0.001; Interaction: P = 0.046 | ||||||
| PCAv CVR (mmHg/cm/sec) | ||||||
| 45°HUT | 2.99 ± 0.28 | 3.12 ± 0.33a | 3.16 ± 0.32a | 3.13 ± 0.30a | 3.13 ± 0.29a | 3.09 ± 0.31a |
| Supine | 2.59 ± 0.24 | 2.84 ± 0.24a | 2.85 ± 0.25a | 2.87 ± 0.25a | 2.92 ± 0.24a | 2.85 ± 0.24a |
| 45°HDT | 2.92 ± 0.25 | 2.98 ± 0.27a | 3.08 ± 0.26a | 3.07 ± 0.25a | 3.04 ± 0.23a | 3.12 ± 0.24a |
| Body Position: P = 0.183; % Protocol: P < 0.001; Interaction: P < 0.542 | ||||||
| PETCO2 (mmHg) | ||||||
| 45°HUT | 31.5 ± 0.9 | 30.3 ± 0.7 | 30.1 ± 0.9 | 29.9 ± 1.0a | 29.2 ± 1.0a | 28.1 ± 0.9a |
| Supine | 31.8 ± 1.1 | 30.0 ± 1.1a | 30.2 ± 1.1 | 30.2 ± 1.0 | 30.3 ± 1.1 | 29.7 ± 1.2a , b |
| 45°HDT | 31.6 ± 0.9 | 30.4 ± 1.1 | 30.1 ± 1.2 | 30.9 ± 1.0 | 30.9 ± 1.0c | 30.3 ± 1.2c |
| Body Position: P = 0.219; % Protocol: P < 0.001; Interaction: P < 0.034 | ||||||
MCAv, middle cerebral artery velocity; MCAv CVR, middle cerebral artery cerebrovascular resistance; PCAv, posterior cerebral artery velocity; PCA CVR, posterior cerebral artery cerebrovascular resistance, PETCO2, partial pressure of end‐tidal carbon dioxide, HUT, head‐up tilt; LBNP, lower body negative pressure; PCA, posterior cerebral artery.
a
P < 0.05, versus baseline.
b
P < 0.05, 45°HUT versus supine.
c
P < 0.05, 45°HUT versus 45°HDT.
P < 0.05, Supine versus 45°HDT. P‐values for main effects and interactions are displayed underneath each variable.