Purpose

Cardiopulmonary bypass (CPB) is a well-established procedure that uses cannulae during cardiac surgery to drain and return blood. In challenging cases (e.g. aortic dissection, reoperation), peripheral cannulation in vessels such as the axillary artery are used. However, standard cannulae at these sites may inhibit blood flow to distal extremities or require grafts that increase surgical time. This study evaluates a novel, flexible-tip arterial cannula designed for bi-directional flow.

Methods

A 22Fr body cannula was developed to achieve a pressure loss (ΔP) < 100 mmHg and 80/20 bi-directional flow distribution between tip outlets. A full factorial design of experiments (2-levels, 4 factors: tip A-width, B-height, C-depth, D-outlet shape) was completed to evaluate sixteen cannula tip designs using benchtop hydraulic and bi-directional flow models. Prototypes were fabricated using 3D printing via stereolithography (Form 3 + , Formlabs, Somerville, MA) with a flexible (50A) cured resin.

Results

The most efficient cannula design (A − , B + , C + , D + ) achieved 4 L/min of total bi-directional flow at a ΔP of 74 mmHg. The average ΔP at 4 L/min for all candidate design was 87 ± 9 mmHg (range 72–100 mmHg). Primary outlet flow distribution averaged 81% ± 6% (range 70–95%) at 1-5 L/min flow rates. Tip width had the greatest influence on ΔP, followed by outlet shape, depth, and their interactions, respectively. Cylindrical and prolate spheroid shaped tips outperformed spherical designs.

Conclusion

The novel cannula demonstrated feasibility and proof-of-concept as evidenced by bi-directional flow with ΔP comparable to commercial cannulae. Future work will involve CFD modeling and pre-clinical validation (e.g. hemolysis, cadaver fit) to support development of a low-cost, clinical grade bi-directional flow cannula for peripheral CPB to reduce surgical complexity and lower risk of adverse events.