Tissue hemoglobin index: a non-invasive optical measure of total tissue hemoglobin

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.

ISSN: 1364-8535