Table 2. Physiologic parameters during baseline and hypercapnia.
| Parameter | Baseline | Hypercapnia | Change from baseline (%) | P-value |
|---|---|---|---|---|
| *SaO2 (%) | 89.3 (84.5, 92.3) | 84.2 (79.1, 88.7) | −3.3 (−8.4, −0.5) | <0.001 |
| *Hb (g/dL) | 13.5 (12.4, 14.2) | 13.7 (12.8, 15.2) | 0.6 (−3.5, 5.4) | 0.28 |
| Ca (mL/dL) | 16.4 (15.1, 17.8) | 15.9 (13.6, 17.6) | −2.2 (−8.1, 2.3) | 0.08 |
| MRI | ||||
| SvO2 [%] | 55.2 (49.3, 60.2) | 66.4 (57.0, 72.5) | 13.2 (3.0, 18.2) | <0.001 |
| OEF | 0.38 (0.26,0.42) | 0.19 (0.14, 0.24) | −51.6 (−59.9, −37.0) | <0.001 |
| CBF (mL/minute per 100 g) | 9.6 (7.5, 15.1) | 21.9 (16.5, 31.0) | 115.8 (83.5, 148.0) | <0.001 |
| CMRO2 (mL O2/minute per 100 g) | 0.49 (0.40, 0.79) | 0.53 (0.40, 0.79) | 4.6 (−31.8, 28.5) | 0.68 |
| Optics | ||||
| StO2 (%) | 49.3 (42.9, 54.7) | 62.7 (51.5, 67.8) | 11.1 (6.9, 19.1) | <0.001 |
| OEF | 0.58 (0.49, 0.68) | 0.28 (0.19, 0.33) | −35.5 (−43.7, −26.7) | <0.001 |
| BFI (10−9 cm2/second) | 17.8 (12.6, 27.0) | 33.5 (23.9, 44.7) | 75.0 (51.4, 87.0) | <0.001 |
| CBV (mL/100 g) | 1.74 (1.46, 2.08) | 2.38 (2.05, 2.72) | 37.3 (23.9, 45.7) | <0.001 |
| CMRO2i (10−7 mL O2/dL × cm2/second) | 1.07 (0.88, 1.87) | 1.23 (0.85, 1.99) | −7.3 (−21.0, 29.9) | 0.86 |
BFI, blood flow index; Ca, arterial oxygen content; CBF, cerebral blood flow; CBV, cerebral blood volume; CMRO2, cerebral metabolic rate of oxygen; CMRO2i, CMRO2 index; Hb, hemoglobin; OEF, oxygen extraction fraction; SaO2, arterial oxygen saturation; SvO2,venous oxygen saturation; StO2, tissue oxygen saturation.
Median and interquartile range of various hemodynamic parameters measured with MRI and optics at baseline and in response to hypercapnia. The P values were obtained from a Wilcoxon two-sided signed-rank test.
*
Determined from arterial blood gas analysis using co-oximetry.