Table 2.
Central hemodynamic responses during progressive LBNP to presyncope in males and females
| LBNP Stage |
P Values |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 15 | 30 | 45 | 60 | LBNP | Sex | Interaction | PS-1 | P value | |
| HR, beats/min | ||||||||||
| Male | 62.3 ± 1.4 | 66.7 ± 1.6* | 73.9 ± 1.8* | 83.7 ± 2.3* | 97.7 ± 3.5* | <0.0001 | 0.98 | 0.72 | 112.7 ± 3.5 | P = 0.36 |
| Female | 64.3 ± 1.7 | 65.6 ± 2.0 | 73.3 ± 2.8* | 85.8 ± 3.5* | 97.2 ± 4.8* | 107.6 ± 4.5 | ||||
| MAP, mmHg | ||||||||||
| Male | 93.6 ± 1.5 | 92.7 ± 1.6 | 89.9 ± 1.7* | 88.1 ± 1.7* | 86.3 ± 1.5* | <0.0001 | 0.80 | 0.90 | 76.2 ± 1.2 | P = 0.62 |
| Female | 94.7 ± 1.8 | 92.2 ± 1.6 | 89.7 ± 1.7* | 87.4 ± 1.9* | 83.6 ± 2.4* | 75.4 ± 0.9 | ||||
| SVi, mL/m2 | ||||||||||
| Male | 51.1 ± 1.3† | 46.2 ± 1.4* | 40.0 ± 1.4* | 33.6 ± 1.2* | 27.1 ± 1.4* | <0.0001 | 0.13 | 0.21 | 23.7 ± 1.3 | P = 0.79 |
| Female | 46.8 ± 1.2 | 44.2 ± 1.3* | 37.8 ± 1.4* | 30.3 ± 1.1* | 24.9 ± 1.1* | 23.2 ± 1.2 | ||||
| Qi, (L/min)/m2 | ||||||||||
| Male | 3.2 ± 0.1 | 3.1 ± 0.1* | 2.9 ± 0.1* | 2.8 ± 0.1* | 2.6 ± 0.1* | <0.0001 | 0.13 | 0.68 | 2.6 ± 0.1 | P = 0.17 |
| Female | 3.0 ± 0.1 | 2.9 ± 0.1 | 2.7 ± 0.1* | 2.6 ± 0.1* | 2.4 ± 0.1* | 2.4 ± 0.1 | ||||
| Qi, %Δ | ||||||||||
| Male | – | −3.7 ± 0.9* | −8.1 ± 1.2* | −12.0 ± 2.0* | −15.2 ± 2.0* | <0.0001 | 0.48 | 0.53 | −16.5 ± 3.7 | P = 0.74 |
| Female | – | −3.2 ± 1.1 | −8.2 ± 1.4* | −13.3 ± 2.0* | −18.4 ± 2.8* | −18.2 ± 3.3 | ||||
| SVRi, (mmHg/L·min−1)/m2 | ||||||||||
| Male | 30.5 ± 1.2 | 31.4 ± 1.3 | 31.9 ± 1.3 | 32.7 ± 1.5* | 34.5 ± 1.7* | <0.0001 | 0.25 | 0.48 | 30.6 ± 1.5 | P = 0.46 |
| Female | 32.2 ± 1.1 | 32.7 ± 1.0 | 33.6 ± 1.1 | 34.8 ± 1.3* | 35.5 ± 1.1* | 32.0 ± 1.2 | ||||
| SVRi, %Δ | ||||||||||
| Male | – | 3.2 ± 1.2 | 4.9 ± 1.8* | 6.9 ± 2.0* | 8.3 ± 2.9* | <0.0001 | 0.66 | 0.34 | 1.2 ± 3.7 | P = 0.97 |
| Female | – | 1.4 ± 1.3 | 4.3 ± 1.7 | 8.8 ± 2.6* | 12.3 ± 3.8* | 1.4 ± 4.4 | ||||
Data are presented as absolute and relative means ± SE. HR, heart rate; LBNP, lower body negative pressure; MAP, mean arterial pressure; Qi, cardiac output index; SVi, stroke volume index; SVRi, systemic vascular resistance index; Δ, change. PS-1 time point refers to the 1 min prior to presyncope. A two-factor linear mixed model analysis with repeated measures from baseline to −60 mmHg LBNP was performed, followed by Holm-corrected post hoc tests for multiple comparisons (run on the least squared means generated by the linear mixed model analysis).
*P ≤ 0.07 compared to baseline within a group. †P ≤ 0.09 between male and female groups. Sex differences at presyncope were assessed using unpaired t tests. Exact P values are reported for all comparisons.