Features of the cardiovascular system and microvascular perfusion

The cardiac output determines the amount of oxygen delivered to the whole organism. VO2 may be calculated according to the formula:

where: Q = cardiac output (L/ min) CaO2 = arterial oxygen content CvO2 = mixed venous oxygen content.

The cardiac output in the healthy resting subject is on average 3.5L/m2 body surface area (BSA) and may increase up to five-fold during exercise or hyperdynamic states like septicaemia. Increased metabolic activity is the main trigger to increase cardiac output, inducing regional vasodilation and favouring increased blood flow in the target organ.

Macrovascular parameters of oxygen utilization do not reflect the distribution of oxygen and its consumption in the various specific organ systems; but microvascular parameters of oxygen utilization are not appropriate for use in the clinical practice

It is essential to understand that limited inferences may be derived from whole body data with respect to individual organ well-being.

In contrast to DO2, tissue pO2 provides a direct measure of cellular oxygenation in the tissue measured. Within any organ, tissue pO2 varies considerably, with some cells being hypoxic and others well oxygenated. These ranges have been described in pO2 histograms51. Mitochondrial oxidative phosphorylation is finally determined by mitochondrial pO2.

0 0

Post a comment