Table 1.
Cardiovascular and PetCO2 responses to head-up tilt after various head-down tilts
| Baseline | HDT1 | HDT2 | Duration at HUT, s |
||||||
|---|---|---|---|---|---|---|---|---|---|
| 5 | 10 | 15 | 20 | 40 | 60 | ||||
| HR, beats/min | |||||||||
| Con | 66.8 ± 10.7 | 74.1 ± 12.1 | 74.6 ± 10.6 | 73.1 ± 9.5 | 74.3 ± 9.0 | 74.9 ± 9.2 | 77.0 ± 11.0 | ||
| −10° | 64.5 ± 12.3 | 63.3 ± 12.4 | 64.4 ± 14.2 | 73.8 ± 14.6 | 76.7 ± 16.0 | 74.7 ± 13.5 | 73.2 ± 12.5 | 74.5 ± 11.3 | 78.0 ± 10.1 |
| −25° | 65.2 ± 11.0 | 61.6 ± 10.4† | 61.6 ± 11.0† | 76.1 ± 13.1 | 78.5 ± 12.5 | 75.7 ± 13.6 | 71.9 ± 12.3 | 73.7 ± 13.3 | 77.6 ± 13.2 |
| −55° | 64.9 ± 10.8 | 58.5 ± 9.9†* | 59.7 ± 10.7†* | 81.2 ± 12.7*#& | 85.3 ± 13.0*#& | 80.9 ± 13.3& | 75.7 ± 11.6 | 76.5 ± 12.4 | 78.6 ± 12.6 |
| MAP, mmHg | |||||||||
| Con | 88.0 ± 11.0 | 86.4 ± 14.7 | 87.7 ± 15.0 | 90.8 ± 13.4 | 93.3 ± 12.9 | 91.9 ± 12.2 | 90.8 ± 11.8 | ||
| −10° | 86.8 ± 12.3 | 89.6 ± 10.7† | 86.0 ± 11.2 | 78.7 ± 13.7& | 81.3 ± 13.4 | 89.2 ± 13.4 | 91.0 ± 12.3 | 92.5 ± 10.6 | 91.8 ± 9.7 |
| −25° | 85.9 ± 12.2 | 88.5 ± 10.8 | 83.8 ± 12.0 | 72.6 ± 15.2&* | 78.9 ± 16.8& | 87.8 ± 13.7 | 92.4 ± 12.8 | 92.1 ± 11.4 | 90.4 ± 11.5 |
| −55° | 84.9 ± 12.5 | 88.1 ± 11.0† | 82.9 ± 13.0* | 62.5 ± 16.8&*# | 71.0 ± 20.4&*# | 84.6 ± 15.2& | 89.8 ± 13.9 | 91.1 ± 11.2 | 89.7 ± 10.9 |
| SV, ml | |||||||||
| Con | 80.4 ± 14.0 | 76.2 ± 16.7 | 68.5 ± 13.4 | 68.5 ± 14.7 | 65.1 ± 12.6 | 63.8 ± 11.7 | 61.5 ± 12.2 | ||
| −10° | 80.8 ± 14.0 | 80.1 ± 13.3 | 82.1 ± 14.4 | 85.5 ± 13.7& | 78.0 ± 15.0& | 72.4 ± 16.2 | 69.7 ± 13.0 | 64.2 ± 11.6 | 60.1 ± 11.1 |
| −25° | 79.5 ± 13.5 | 78.6 ± 13.4 | 81.3 ± 14.0 | 87.8 ± 15.2& | 82.1 ± 16.1& | 75.2 ± 15.4& | 72.0 ± 13.8 | 66.6 ± 12.7 | 62.5 ± 12.1 |
| −55° | 80.1 ± 13.4 | 75.4 ± 14.4* | 76.0 ± 13.6*# | 85.5 ± 15.0& | 83.6 ± 19.2& | 75.2 ± 18.6 | 70.6 ± 15.2 | 65.0 ± 14.1 | 60.7 ± 12.0 |
| QMF, l/min | |||||||||
| Con | 5.3 ± 1.2 | 5.4 ± 1.2 | 4.9 ± 1.0 | 4.9 ± 0.9 | 4.7 ± 0.7 | 4.7 ± 1.0 | 4.6 ± 1.0 | ||
| −10° | 5.1 ± 1.2 | 5.1 ± 1.3 | 5.2 ± 1.3 | 6.2 ± 1.3& | 5.8 ± 1.1& | 5.3 ± 1.2 | 5.0 ± 1.3 | 4.7 ± 1.2 | 4.6 ± 1.1 |
| −25° | 5.1 ± 1.2 | 4.8 ± 1.1† | 5.0 ± 1.1 | 6.5 ± 1.2& | 6.3 ± 1.3&#* | 5.5 ± 1.2& | 5.0 ± 1.0 | 4.8 ± 1.2 | 4.7 ± 1.2 |
| −55° | 5.1 ± 1.1 | 4.4 ± 1.0†*# | 4.5 ± 1.0†*# | 6.7 ± 1.3&* | 6.9 ± 1.1&* | 5.9 ± 1.3&* | 5.2 ± 1.3 | 4.8 ± 1.4 | 4.7 ± 1.3 |
| PetCO2, mmHg | |||||||||
| Con | 28.5 ± 3.0 | 26.9 ± 3.3 | 27.0 ± 3.5 | 27.7 ± 3.3 | 27.9 ± 3.1 | 28.0 ± 3.7 | 27.2 ± 3.9 | ||
| −10° | 29.3 ± 3.2 | 29.5 ± 3.0 | 29.4 ± 2.7 | 27.1 ± 3.0 | 27.2 ± 3.1 | 27.3 ± 2.7 | 27.4 ± 2.8 | 27.7 ± 3.0 | 28.0 ± 3.6 |
| −25° | 28.8 ± 3.1 | 28.9 ± 3.3 | 28.2 ± 3.2 | 27.6 ± 2.9 | 27.1 ± 3.3 | 27.2 ± 3.5 | 27.5 ± 3.5 | 27.6 ± 3.4 | 27.1 ± 3.4 |
| −55° | 28.9 ± 2.9 | 28.6 ± 3.6 | 28.6 ± 3.0 | 27.7 ± 3.0 | 27.5 ± 2.7 | 27.8 ± 3.6 | 28.3 ± 3.3 | 28.0 ± 3.1 | 27.5 ± 3.6 |
Data are expressed as means ± SD; n = 10.
HR, heart rate; MAP, mean arterial pressure; SV, stroke volume; QMF, cardiac output calculated by way of Modelflow; PetCO2, end-tidal Pco2; HDT1: HDT at 0–7 s; HDT2: HDT at 8–15 s.
HUT of 5: 0–5 s; 10: 6–10 s; 15:11–15 s; 20: 16–20 s; 40: 21–40 s; 60: 41–60 s. P < 0.05: significantly different †vs. baseline, &vs. control,
*
vs. −10° HDT condition, #vs. −25° at same period.