Peripheral Vascular Loops urges practitioners to consider their patients capillary pressures when prescribing fluids or vaso-active medications, as the Steady State Starling Principle dictates that interstitial fluid volume can be rapidly increased by hyperfiltration caused by injudicious ‘bolus’ fluid therapy, while the lymphatic drainage of interstitial fluid is slow. Jv is a one-way street; there is no reabsorption of ISF to the capillary that delivered the filtrate.

I was therefore intrigued and delighted to be approached by Mr Charles L. Davis, inventor and patent holder in Vancouver, WA in the USA. Charles has developed the technology to measure capillary pressure non-invasively. If it turns out to be deliverable and practicable we could put an end to the toll of iatrogenic fluid overload in our ICUs. I am assisting Mr Davis on his life-saving mission as an unpaid medical advisor.

Mr Davis has ambitions to change the way clinicians think about haemodynamics and control of the circulation.

No one knows better than me the inertia one finds when trying to explain “New” or “Revised” physiological concepts to an audience who believe they learned all they need to know in Med School several years ago. In future blogs I’ll explore in more detail Davis’ peripheral vascular loop model. In the land of PVL the role of the heart is relegated to that of a slave pump which pressures-up the venous return to the cardiac output. The arterial system resists flow in order to generate a regulated perfusion pressure head for the organs and tissues of the body. The capillaries are the interface between intravascular and extravascular ECF circulations. Finally, the venous system assists flow by accomodating a stressed blood volume (remember the venous excess concept) which regulates venous return/ cardiac output.


So what is CVP in the land of Peripheral Vascular Loops? CVP is the pressure that remains (not dissipated by vascular resistance in the PVL segments) after the blood has taken its trip around the PVL along the pathway of flow. It remains a valid clinical tool which can also be monitored non-invasively.

If this is a potential vision of future EM/ ICU practice that excites you, bookmark and come back frequently!

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