Stress, strain, ignorance and reinventing the wheel: Understanding central venous pressure
An understanding of the physics, physiology and pathophysiology underpinning the use of the central venous pressure is essential in the effective use thereof. As for any hollow organ, the interaction between intracavity volume and pressure of the container is not linear. Because of this characteristic stress and strain relationship, the central venous pressure cannot be a simple and static indication of the volume inside the container and should neither be used as such nor should across the board comparisons between central venous pressure measurements and other markers of intravascular volume be attempted. Dynamic testing of the system stiffness (elastance) of the container is an effective but still indirect manner to gauge the particular intracavity volume.
Keywords: asthma; child; anaesthesia; bronchospasm