A two-phase fluid volume compensation chamber for an electric ventricular assist device

Area of Science:

• Biomedical Engineering
• Mechanical Engineering
• Fluid Dynamics

Background:

• Electric ventricular assist devices (EVADs) experience significant pressure fluctuations during operation.
• These pressure variations can negatively impact device performance and longevity.
• Minimizing pressure swings is critical for ensuring the reliable function of EVADs.

Purpose of the Study:

• To investigate the impact of motor casing pressure variation on the Penn State EVAD's performance.
• To establish design criteria for acceptable pressure swing and optimal operating pressure for EVADs.
• To develop and evaluate a novel volume compensation chamber to mitigate pressure fluctuations.

Main Methods:

• Design criteria were established for maximum pressure swing and optimal mean chamber pressure.
• A two-phase fluid volume compensation chamber utilizing Freon and a high-heat-flux porous coating was developed.
• The chamber was isolated from the EVAD using a metal bellows.
• Pressure swing was measured in coated and uncoated chambers at various beat rates and Freon volumes.

Main Results:

• At -15 mm Hg mean chamber pressure, pressure swing must be below 45 mm Hg for adequate EVAD performance.
• The developed volume compensation chamber significantly reduced pressure swing, up to 50% with the high-flux coating.
• The coated chamber maintained pressure swings between 22-30 mm Hg at 60 beats/min across a wide volume range (4-38 ml).
• Acceptable pressure swings were observed even at 100 beats/min with the coated chamber.

Conclusions:

• The developed two-phase fluid volume compensation chamber effectively reduces pressure swings in EVADs.
• The high-heat-flux porous coating is crucial for the chamber's enhanced performance.
• This technology ensures adequate pump performance and offers a promising solution for improving EVAD reliability.