Model for the physics and physiology of fluid administration

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Clinical Medicine

Background:

• Understanding fluid flow in intravenous systems is crucial for safe and effective drug delivery.
• Current clinical infusion devices require a robust model to explain their behavior in various physiological conditions.
• The pressure-flow relationship (PFR) is a key parameter in characterizing fluid dynamics in biological systems.

Purpose of the Study:

• To develop and validate a model for understanding fluid flow in intravenous systems and human subjects.
• To represent common clinical situations, including venous obstruction and fluid extravasation, using a unified model.
• To characterize the pressure-flow relationship (PFR) of physical devices and the patient's venous system.

Main Methods:

• Physical devices modeled as ideal resistors, pressure sources, and flow sources.
• Patient's venous system modeled as a combination of ordinary and Starling resistors.
• Experimental validation to demonstrate the model's ability to represent clinical situations.

Main Results:

• Both physical devices and patients are adequately represented by a linear PFR (pressure = opening pressure + flow X resistance) for flows between 0 and 300 ml/hr.
• Normal vein PFR: low resistance (22 +/- 20 mm Hg/L/hr) and low opening pressure (15 +/- 8 mm Hg).
• Partially obstructed vein PFR: similar resistance, elevated opening pressure. Perivascular tissue PFR: high resistance (1,125 +/- 1,376 mm Hg/L/hr), variable opening pressure.

Conclusions:

• The developed model accurately represents fluid flow in intravenous systems and common clinical scenarios.
• The PFR model provides insights into vein obstruction and fluid extravasation, explaining device behavior.
• This model can enhance the understanding and clinical application of intravenous infusion devices.