Note that the VA- and VV-ECMO systems are both accessed through <Devices><ECMO System> menu item and that the ECMO system is switched between these modes using the control at the bottom right-hand side of the ECMO system interface.
The Veno-venous ECMO module is intended for use by those undergoing training in this technique and is intended for use in a patient suffering from extreme respiratory failure. (Qs/Qt > 50%; Vd/Vt > 50%). The module has three user interfaces:
The Pump Control Interface (PCI) is loosely-based on the Maquet 'CardioHelp' perfusion system.
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To the left of the interface are three controls which control respectively the inspired oxygen concentration (%) of gas flowing through the oxygenator; the flow rate (lpm) to the oxygenator; and the temperature setting control (C) for the heater: cooler. In the context of VV ECMO, the FiO2 control should always be set at 100%. The flow rate control is used to control CO2 elimination (the higher the gas flow rate, the greater the rate of CO2 clearance). The heater: cooler can be used to vary the patient’s temperature (and their metabolic rate).
Between these three controls and the ‘CardioHelp’ data display area is the electronic clamp which controls flow through the outlet (‘Arterial’) side of the pump. When the slider is at the bottom, the clamp is fully closed, when at the top, fully open.
The data display area displays the current values of:
| • | Flow through the system in lpm, |
| • | Circuit pressure measured at a point between the pump head and the oxygenator, |
| • | Venous oxygen saturation, |
| • | Pump speed in rpm, |
| • | Haematocrit and |
| • | Blood Temperature. |
To the right of the display area are four controls:
| • | The main power switch enables the flow control knob which is situated just beneath it. |
| • | The flow control is used to adjust the speed of the centrifugal pump in the range 0 – 5000 rpm. |
| • | The <Adjust Cannula> button allows you to move the drainage cannula(e) in or out and to select size of your return cannula. |
| • | Finally, the <Mode> button is used to set the system up for either VV or VA ECMO. |
By default, the PCI assumes that venous drainage is via a femoral vein through a 24F catheter and that arterialised return is via a jugular vein through a 21F catheter. The tip of the jugular catheter has been correctly positioned (using ultrasound) with its tip in the mid-atrial position.
Cannula Adjustment Interface:
The cannula adjustment interface is used to advance or withdraw the femoral drainage catheter using the slide-control at the left. If the tips of the drainage and return cannulae are positioned too closely, re-circulation will start to occur and oxygenation will be impaired.
If satisfactory conditions cannot be obtained using a single drainage cannula, the 'Dual Cannulation' box should checked, and a second slide will appear which will enable the positioning of a second (SVC) cannula.
Clicking the <Select Return Cannula> button opens up the Cannula Selector window.
Return Cannula Selector Interface:
Select the cannula size that you want and then click <Save> to close the window. Click <Devices><ECMO System> to return to the ECMO system itself.