Blood flow pulsatility effects upon oxygen transfer in artificial lungs

Area of Science:

• Biomedical Engineering
• Cardiovascular Physiology
• Respiratory Support Devices

Background:

• Artificial lungs are crucial for respiratory support, but their efficiency can be affected by blood flow dynamics.
• Understanding the impact of pulsatile flow, mimicking natural cardiac output, is essential for optimizing artificial lung performance.

Purpose of the Study:

• To investigate the theoretical and experimental effects of pulsatile blood flow on oxygen transfer rates in artificial lungs.
• To apply quasi-steady gas transfer theory to pulsatile flow conditions and validate it with in vitro experiments.
• To inform the design of artificial lungs, particularly implantable thoracic devices, by considering flow pulsatility.

Main Methods:

• Developed a theoretical model applying steady-state gas transfer principles to instantaneous pulsatile flow rates (quasi-steady approach).
• Conducted in vitro experiments using bovine blood, pediatric oxygenators, a pulsatile pump, and a compliance chamber.
• Measured oxygen transfer rates under both steady and pulsatile flow conditions to compare performance.

Main Results:

• Theoretical models predicted reduced oxygen transfer rates for pulsatile flow compared to steady flow at equivalent mean flow rates.
• In vitro tests demonstrated an average 10% reduction in oxygen transfer with pulsatile flow versus steady flow.
• Theoretical predictions aligned well with experimental measurements, validating the quasi-steady gas transfer model.

Conclusions:

• Blood flow pulsatility significantly reduces oxygen transfer efficiency in artificial lungs.
• Incorporating a compliant section in thoracic artificial lungs is recommended to dampen cardiac pulse effects and improve gas transfer.
• Even minimal compliance (0.2 ml/mm Hg) can restore oxygen transfer efficiency to approximately 95% of steady-flow levels.