Table 2. Transit time characteristics during activation, estimated from literature red blood cell velocity data.
| MTT (seconds) | CTH (seconds) | CMRO2 original model | CMRO2 new model | PtO2 new model | CBF | |
|---|---|---|---|---|---|---|
| Functional activation10 | ||||||
| Control (0) | 1.4 | 1.33 | 1.00 | 1.00 | 1.00 | 1.00 |
| Activation (I) | 0.81 | 0.52 | 1.50 (1.46) | 1.10 (7.3) | 1.55 (1.32) | 1.73 |
| Cortical electrical stimulation9 | ||||||
| Control (0) | 1.49 | 0.92 | 1.00 | 1.00 | 1.00 | 1.00 |
| 1.0 mA (I) | 1.71 | 1.20 | 0.89 (1.2) | 0.97 (3.9) | 0.88 (1.1) | 0.87 |
| 2.0 mA (II) | 1.14 | 0.74 | 1.17 (1.8) | 1.03 (11) | 1.17 (1.8) | 1.31 |
| 3.0 mA (III) | 0.96 | 0.55 | 1.31 (1.8) | 1.05 (11) | 1.33 (1.7) | 1.55 |
| 4.0 mA (IV) | 0.62 | 0.32 | 1.64 (2.2) | 1.08 (17) | 1.66 (2.1) | 2.40 |
| 5.0 mA (V) | 0.63 | 0.23 | 1.64 (2.1) | 1.09 (16) | 1.70 (2.0) | 2.36 |
| Hypotension40 | ||||||
| 115 mm Hg (0) | 0.30 | 0.10 | 1.00 | 1.00 | 1.00 | 1.00 |
| 90 mm Hg (I) | 0.31 | 0.11 | 0.99 (2.3) | 0.99 (34) | 0.99 (2.7) | 0.97 |
| 75 mm Hg (II) | 0.34 | 0.15 | 0.94 (2.0) | 0.99 (27) | 0.95 (2.3) | 0.88 |
| 50 mm Hg (III) | 0.40 | 0.16 | 0.89 (2.3) | 0.99 (32) | 0.91 (2.7) | 0.75 |
| 30 mm Hg (IV) | 0.69 | 0.30 | 0.70 (1.9) | 0.97 (20) | 0.73 (2.1) | 0.43 |
| Mild hypoxemia11 | ||||||
| Control (0) | 0.95 | 0.36 | 1.00 | 1.00 | 1.00 | 1.00 |
| 40 mm Hg (I) | 0.72 | 0.31 | 0.89 (−2.9) | 0.90 (−3,2) | 0.46 (−0.59) | 1.32 |
| Severe hypoxemia12 | ||||||
| Control (0) | 1.41 | 1.20 | 1.00 | 1.00 | 1.00 | 1.00 |
| 26 mm Hg (I) | 0.87 | 0.63 | 0.69 (−2) | 0.77 (−1.8) | 0.29 (−0.87) | 1.62 |
| Mild hypercapnia7 | ||||||
| 33 mm Hg (0) | 1.29 | 1.02 | 0.31 | 1.00 | 1.00 | 1.00 |
| 50 mm Hg (I) | 0.82 | 0.76 | 0.24 (2.5) | 1.04 (15) | 1.24 (2.4) | 1.57 |
| Severe hypercapnia11 | ||||||
| 35 mm Hg (0) | 0.59 | 0.25 | 1.00 | 1.00 | 1.00 | 1.00 |
| 67 mm Hg (I) | 0.43 | 0.29 | 1.09 (4.2) | 1.00 (88) | 1.07 (5.2) | 1.37 |
| 97 mm Hg (II) | 0.37 | 0.29 | 1.13 (4.6) | 1.01 (93) | 1.10 (5.7) | 1.59 |
Oxygen consumption (CMRO2) and tissue oxygen tension (PtO2) predicted by the original and the new model (relative to control) are indicated. Cerebral blood flow (CBF) (relative to baseline) is given assuming a fixed capillary volume and derived from the central volume theorem. Transit time distribution is assumed to be described by a gamma variate function. As it is discussed in the main text, neurovascular coupling indices are reported in parenthesis, and correspond to the ratio of the increase in CBF over the increase in CMRO2. For PtO2, the number in parenthesis corresponds to the increase in CBF over the increase in PtO2, and can be seen as a coupling index analogy for PtO2. Physiologic conditions were assigned symbols and roman numerals to allow identification in Figures 4, 5, 6.