Characterizing the impact of minor cannula design modification

Area of Science:

• Cardiovascular Surgery
• Biomedical Engineering
• Fluid Dynamics

Background:

• Venous cannulas are critical for cardiopulmonary bypass (CPB).
• Evaluating cannula hydrodynamic performance is essential for optimizing CPB procedures.
• The impact of connecting tube diameter on cannula performance requires detailed investigation.

Purpose of the Study:

• To assess the effect of extracorporeal connecting tube internal diameter on venous cannula performance.
• To quantify changes in flow rate (Q), pressure drop (delta P), and cannula resistance (delta P/Q²) with varying tube diameters.
• To compare the hydrodynamic efficiency of different venous cannula models.

Main Methods:

• An in vitro circuit was established using silicone tubing and test cannulas.
• High-fidelity pressure transducers measured pressure drop (delta P) between drainage and preload pressures.
• An ultrasonic flowmeter quantified flow rate (Q), with data managed by virtual instruments.

Main Results:

• Increasing connecting tube diameter from 8 mm to 9 mm reduced resistance by 17% for the 27 F smartcanula®.
• Flow rate (Q) increased from 7.22±0.1 to 7.81±0.04 L/min for 8 mm and 9 mm smartcanula® tubes, respectively.
• The 27 F smartcanula® demonstrated 13% higher flow rates than the 28 F Medtronic cannula (p<0.0001).

Conclusions:

• Larger connecting tube diameters significantly increase flow rate (Q) and decrease pressure drop (delta P) and resistance (delta P/Q²) in venous cannulas.
• Connecting tube diameter is a critical factor influencing liquid flow resistance through cannulas.
• Smartcanulas® exhibit superior hydrodynamic performance compared to Medtronic cannulas.