Table 3.
THI and StO2 measurements in 30 healthy human volunteers before, during, and after acute ischemia
| Experimental condition | Tissue hemoglobin index | Tissue hemoglobin oxygen saturation |
|---|---|---|
| Head-of-bed elevation (no ischemia) | *0°, 60° | *0°, 30°, 60° |
| 0° | 14.6 ± 1.68 | 81.5 ± 5.11 |
| 30° | 15.0 ± 1.60 | 78.7 ± 5.17 |
| 60° | 15.2 ± 1.66 | 75.3 ± 5.86 |
| Arterial cuff occlusion | *All except baselines | *All except baselines |
| Baseline | 14.6 ± 1.68 | 82.0 ± 5.33 |
| End | 10.6 ± 1.81 | 28.2 ± 10.9 |
| Recovery peak | 18.7 ± 2.71 | 95.3 ± 1.86 |
| Recovery baseline | 14.8 ± 1.61 | 82.1 ± 4.57 |
| Venous cuff occlusion | *All except baselines | *All except baselines |
| Baseline | 14.8 ± 1.61 | 82.1 ± 4.45 |
| End | 16.2 ± 1.53 | 68.4 ± 6.84 |
| Recovery baseline | 14.5 ± 1.74 | 79.6 ± 4.90 |
| Esmarch bandage exsanguination | *All | *All |
| Nadir | 7.0 ± 1.56 | 31.7 ± 19.3 |
| Residual (calculated, Equation (2)) | 3.7 ± 2.0 | Not applicable |
| Recovery peak | 16.2 ± 2.49 | 92.1 ± 3.63 |
| Recovery baseline | 13.7 ± 1.90 | 78.1 ± 6.58 |
| Demographic characteristics | ||
| Age (years) | 41.8 ± 9.09 | |
| Height (inches) | 68.6 ± 3.47 | |
| Weight (pounds) | 171 ± 30.6 | |
| Body mass index (kg/m2) | 25.5 ± 3.68 | |
| Systolic blood pressure (mmHg) | 126 ± 7.9 | |
| Diastolic blood pressure (mmHg) | 78 ± 8.0 | |
| Mean arterial pressure (mmHg) | 94 ± 7.4 | |
| Heart rate (beats/minute) | 67 ± 11.6 |
Data presented as mean ± one standard deviation. Baseline measurements were obtained before inducing ischemia. All ischemia and ischemia recovery measurements were performed at 0° bed elevation. The tissue hemoglobin index (THI) mean was manipulated from 7.0 to 18.7 under conditions of constant blood hemoglobin concentration. *Rows having statistically different means, P < 0.05. StO2, tissue hemoglobin oxygen saturation.