The effect of return cannula size on performance.
In the figure above, I've used the simulator to find out what rpm's and pressures are required to generate a flow of 5.0 lpm through a VV ECMO circuit when the size of the return cannula is varied between 15 and 23 F and drainage is unrestricted.
The data are modelled on the behaviour of a 'Rotaflow' pump and a 'Quadrox D' oxygenator.
As can be seen, when a small return cannula is selected, the driving pressure and pump speed required to generate the flow are much higher. This may be associated with:
- Increased shear stress on the formed elements of the blood,
- an increase in platelet activation,
- an increased likelihood of circuit disruption,
- an increase in the operating temperature of the pump head.