Fig. 1
From: “THE MANTLE” bundle for minimizing cerebral hypoxia in severe traumatic brain injury
A Oxygen, O2 route. From atmospheric air or the gaseous mixture supplied by mechanical ventilation, O2 travels following concentration gradients. Cerebral O2 transport (CerO2t) depends on the product of CBF and arterial O2 content (CaO2), determined by the following equation: CaO2 = (Hgb × 1.34 x SaO2) + (PaO2 × 0.003), where: Hgb: concentration in gr/dl; 1.34: number of ml transported by each gram of Hgb; SaO2: arterial O2 saturation; PaO2: arterial pressure of O2. The affinity of oxygen for Hgb is expressed by analyzing the Hgb-oxygen saturation curve. The CBF is mainly determined by the cerebral perfusion pressure (CPP) and the radius of the cerebral resistance vessels (autoregulation curve). B O2 diffusion at cellular level. If the physiological variables interact harmoniously, oxygen reaches the microcirculation at 98 mmHg, then diffuses into the cell through the interstitial space (PO2i = 20–40 mmHg). Inside the cell, the O2 pressure is 1.5 mmHg. The distance that the 02 must travel varies between 20 and 60 microns