Respiratory gas exchange and circulatory responses during orthostatic tolerance test at rest and after 8 minutes standing in healthy controls and in patients with HVS
| Controls (n = 13) | HVS patients (n = 16) | |||||
|---|---|---|---|---|---|---|
| At rest | Standing | Change | At rest | Standing | Change | |
| BF (/min) | 14.5 (0.8) | 14.9 (0.9) | 0.4 (–0.5 to 1.3) | 14.0 (1.1) | 17.9 (1.1) | 3.9 (1.5 to 6.2)2-150 |
| V˙e (l/min) | 8.1 (0.6) | 9.3 (0.6) | 1.2 (0.5 to 1.9) | 7.7 (0.9) | 14.2 (1.8)2-150 | 6.5 (3.5 to 9.6)2-150 |
| RQ | 0.79 (0.03) | 0.77 (0.02) | –0.02 (–0.06 to 0.09) | 0.87 (0.04) | 0.91 (0.03)2-150 | 0.04 (–0.02 to 0.10) |
| Fetco 2(%) | 4.27 (0.12) | 4.18 (0.08) | –0.09 (–0.26 to 0.09) | 4.18 (0.13) | 3.12 (0.16)2-165 | –1.05 (–1.30 to –0.81)2-165 |
| V˙e/V˙o 2 | 31.0 (1.2) | 32.2 (1.0) | 1.2 (0.5 to 2.0) | 36.4 (1.9) | 50.6 (3.9)2-165 | 14.3 (8.5 to 20.0)2-160 |
| V˙e/V˙co 2 | 39.2 (1.7) | 41.8 (1.3) | 2.7 (1.3 to 4.0) | 41.9 (1.3) | 53.6 (2.4)2-165 | 11.7 (7.2 to 16.2)2-150 |
| HR (/min) | 65.0 (1.8) | 77.1 (2.9) | 12.1 (7.8 to 16.3) | 72.9 (1.9)2-150 | 93.4 (3.7)2-160 | 20.5 (15.3 to 25.7)2-150 |
| Systolic BP (mm Hg) | 122 (4.2) | 125 (3.9) | 4 (–1 to 8) | 135 (4.3)2-150 | 137 (5.9) | 1 (–7 to 9) |
↵2-150 p<0.05;
↵2-160 p<0.01;
↵2-165 p<0.001 compared with controls (Mann-Whitney U test).
The results within groups are expressed as mean (SE) and the changes as mean (95% confidence intervals).
BF = breathing frequency; V˙e = minute ventilation; RQ = respiratory exchange ratio; Fetco 2 = end expiratory tidal CO2 fraction;V˙e/V˙o 2,V˙e/V˙co 2 = ventilatory equivalents for O2 and CO2; HR = heart rate; BP = blood pressure.