Relationship Between Cerebral Oxygenation and Skin Blood Flow at the Frontal Lobe during Progressive Hypoxia: Impact of Acute Hypotension.

We investigated the relationship between cerebral oxygenation (COX) and skin blood flow (SkBF) at the left frontal lobes of 10 healthy young men during progressive hypoxia (∼ -1 h at each of 21%, 18%, 15%, and 12% of inspired oxygen [FiO2]). Acute hypotension was manipulated by a thigh-cuff-release technique, where a pressure of 220 mmHg was applied at both thigh muscles for 3 min and the cuff was immediately released to induce acute hypotension. While the resting baseline for COX before the thigh-cuff release manipulation decreased gradually with the reduction of FiO2 (P < 0.05), the resting baseline for SkBF, mean arterial blood pressure (MAP), and cutaneous vascular conductance (CVC) were unaffected by FiO2 (P > 0.05). The acute hypotension that was induced by the thigh-cuff release decreased COX, SkBF, MAP, and CVC; thereafter, these values recovered toward their baseline values. During the hypotension phase, while the time to the nadir values for COX slowed progressively with reductions in FiO2 (P < 0.05), those for SkBF, MAP, and CVC were unaffected by FiO2 (P > 0.05). These results suggest that COX may not be associated with SkBF for the protocol or with the subjects in the present study.